QfotuKll Inioeraita Blibtarg 3tl{aca. Nem ^nvk THE LIBRARY OF EMIL KUICHLING, C. E. ROCHESTER. NEW YORK THE GIFT OF SARAH L. KUICHLING 1919 Cornell University Library TN 260.M91 Elements of mineralogy, crystallography 3 1924 005 009 752 M Cornell University ya Library The original of tiiis book is in tine Cornell University Library. There are no known copyright restrictions in the United States on the use of the text. http://www.archive.org/details/cu31924005009752 ELEMENTS Mineralogy, Crystallography Blowpipe Analysis FROM A PRACTICAL STANDPOINT INCLUDING A DESCRIPTION OF ALL COMMON OR USEFUL MINERALS, THE TESTS ' NECESSARY FOR THEIR IDENTIFICATION, THE RECOGNITION AND MEASUREMENT OF THEIR CRYSTALS, AND A CONCISE STATEMENT OF THEIR USES IN THE ARTS ALFRED J. MOSES, E.M., Ph.D. Professor of Mineralogy, Columbia University, New York City CHARLES LATHROP PARSONS, B.S. Professor of General and Analytical Chemistry, New Hampshire College, Durham, N. H. New Enlarged Ed-jtion Parts I and IV Rewritten. Parts II and III Extensively Revised With 664 Figures and 413 Pages of Text NEW YORK D. VAN NOSTRAND COMPANY 190Q Entered according to the Act of Congress in the year 1900, by A. J. MOSES AND C. L. PARSONS, In the Office of the Librarian of Congress. All rights reserved. M L 5. ^HE NEW ERA PRINTING COMPANY, LANCASTERj PA. PREFACE. In this edition of our text-book we have adhered to the de- sign of the edition of 1895, to present the facts leading to a use- ful knowledge of mineralogy in such a manner that the student in the technical school and the professional man in the field may readily learn to recognize or, when necessary, to determine all important minerals. We have made a number of changes and additions which experience has shown to be desirable. Some of these are : Part I., Crystallography, has been entirely rewritten to conform to the now accepted classification, and under each class there have been assembled combinations found in definite species. Over one hundred figures have been added. Part II., Blowpipe Analysis, has been carefully revised, new figures drawn and discussions of the use of the spectroscope, and of metallic sodium added. Part III., Descriptive Mineralogy, now includes about forty pages designed as an introduction to the later study of minerals in thin sections under the microscope. The cuts throughout the descriptive portion are new and the faces of crystal figures are let- tered to facilitate the recording of angles. All crystallographic descriptions and economic discussions have been rewritten. Part IV., Determinative Mineralogy, has been entirely rewrit- ten and greatly simplified. Many suggestions have been made to us by instructors using the book. In so far as possible we have acted upon these sug- gestions and we sincerely hope that the new edition may receive approval. TABLE OF CONTENTS. Part I. — Crystallography. Chapters I. to X., Pages i TO 8i. Chapter I. Introductory, i-ii Chapter II. The Isometric System, 12-22 Chapter III. The Tetragonal System, 23-32 Chapter IV. The Hexagonal System , 3 3-4 7 Chapter V. The Orthorhombic System, 48-54 Chapter VI. The Monoclinic System, 55-6° Chapter VII. The Triclinic System, 61-64 Chapter VIII. Twinned Crystals, 65-71 Chapter IX. Measurement of Crystal Angles, 72-75 Chapter X. Crystal Projection or Drawing, 76-81 Part II. — Blowpipe Analysis. Chapters XI. to XIV., Pages 83 to 135. Chapter XI. Apparatus Blast, Flame, etc., 83-89 Chapter XII. Operations of Blowpipe Analysis,... 90-109 Chapter XIII. Summary of Useful Tests with the Blowpipe, II 0-124 Chapter XIV. Schemes for Qualitative Blowpipe Analysis, 125-135 Part III. — Descriptive Mineralogy. Chapters XV. to XXXV., Pages 137 to 395. Chapter XV. Characters of Minerals, 137-153 Chapter XVI. Optical Characters, 154-163 Chapter XVII. Optical Characteristics of the Differ- ent Crystal Systems 164-179 Chapter XVIII. The Thermal, Magnetic and Electrical Characters, 180-186 Chapter XIX. Chemical Composition and Reactions, 187-193 Chapter XX. The Iron Minerals, 194-213 vi CONTENTS. Part III. — Descriptive Mineralogy — Continued. Chapter XXI. The Manganese Minerals, 214-218 Chapter XXII. Nickel and Cobalt Minerals, 219-226 The Cobalt Minerals, 219 The Nickel Minerals, 222 Chapter XXIII. Zinc and Cadmium Minerals, 227-233 The Zinc Minerals, 227 The Cadmium Minerals, — 233 Chapter XXIV. Tin, Titanium and Thorium Minerals, 234-240 The Tin Minerals, 234 The Titanium Minerals, 236 The Thorium Minerals, 239 Chapter XXV. Lead and Bismuth Minerals, 241-254 The Lead Minerals, 241 The Bismuth Minerals, 251 Chapter XXVI. Arsenic, Antimony, Uranium and Molybdenum Minerals, 255-262 The Arsenic Minerals, 255 The Antimony Minerals, ... 257 The Uranium Minerals, 260 The Molybdenum Minerals, 261 Chapter XXVII. The Copper Minerals, 262-275 Chapter XXVIII. Mercury and Silvef Minerals, 276-285 The Mercury Minerals, 276 The Silver Minerals, 278 Chapter XXIX. Gold, Platinum and Iridium Min- erals, 286-290 The Gold Minerals, 286 The Platinum and Iridium Min- erals, 289 Chapter XXX. Potassium, Sodium and Ammonium Minerals, 291-297 The Potassium Minerals, 291 The Sodium Minerals, 293 The Ammonium Minerals, . 297 Chapter XXXI. Barium and Strontium Minerals, 298-302 The Barium Minerals, 298 The Strontium Minerals, 300 Chapter XXXII. Calcium and Magnesium Minerals,.... 303-320 The Calcium Minerals, 303 The Magnesium Minerals, ..317 C0^ TENTS. vii Part III. — Descriptive Mineralogy — Continued. Chapter XXXIII. The Aluminum Minerals, 318-330 Chapter XXXIV. Boron, Sulphur, Tellurium, Hydro- gen and Carbon Minerals,.... 331-342 The Boron Minerals, 331 The Sulphur and Tellurium Min- erals 335 The Hydrogen Minerals,. ....337 The Carbon Minerals, 338 Chapter XXXV. Silica and the Silicates, 343-395 Silica, 346 Polysilicates, 351 Metasilicates, 357 Orthosilicates, 367 Basic- or Subsilicates, 381 Hydrous Silicates, 383 Titano-Silicates, 395 Part IV. — Determinative Mineralogy. Pages 397 to 399 AND Insets. Chapter XXXVI. Tables for Rapid Determination of the Common Minerals, 397 I. Minerals of Metallic or Subme- tallic Lustre. II. Minerals of Non Metallic Lustre, A. With Decided Tastes, that is. Soluble in Water. B. Without Taste but yielding Coating or Magnetic Residue when Heated on Charcoal. C. Tasteless, non Volatile and NOT made Magnetic by Heating on Charcoal. Table of Atomic Weights, 399 General Index, 4° 1-409 Index 10 Minerals, 41 0-4 1 3 PART I. CRYSTALLOGRAPHY. CHAPTER I. INTRODUCTORY. Crystals and Crystallization. Crystals are formed only when a chemical element or a chem- ical compound solidifies. Broadly speaking every such solidifica- tion is a crystallization and must result in the formation of either : (a). Crystals,* that is, distinct solids bounded by plane faces at definite angles to each other, or {/>). Masses which are aggregations of crystals, that have been hindered in development by lack of space or time or other cause. It is assumed that the invisible molecules of the substance dur- ing solidification are so drawn together that each becomes the center of a precisely similar group, and that along any line, and all parallel lines, the particles are equally far apart. Certainly in a solidification the first visible solid particles, are bounded by plane faces at definite angles to each other, and although at later stages of the solidification the crystals may be larger, the angles between the faces do not change. That a regular arrangement of the particles has taken place can be shown even in the absence of distinct crystals. For instance, solid masses will often break or cleave in directions parallel to certain crystal faces yielding frequently polyhedral solids absolutely constant in angles, no matter how far the cleaving is continued or how small the resulting solids may be. It is also thoroughly * By the term " crystal ' ' was originally meant the colorless quartz still called rock crystal, which was found in geometric solids in many localities and supposed to be water frozen at an e»tremely low temperature. 2 CRYSTALLOGRAPHY. proved that in definite chemical solids the velocity of transmission of light, is exactly the same in all parallel directions, but is not necessarily or even generally the same in directions ' not parallel ; whereas in glass or other homogeneous solids which are not defi- nite chemical compounds the velocity of transmission is, generally speaking, the same in all directions and portions, or if unlike it is without any regularity of difference. The same constancy for parallel directions and variation for di- rections not parallel is shown for other physical characters such as expansion from heat, conductivity of heat or electricity, and even color and lustre, proving beyond reasonable doubt the regular constant arrangement of the particles in straight lines and planes. LAWS OF CRYSTALS. The polyedral solids or crystals which so frequently result from a solidification are infinite in variety. Each substance may occur in a large number of different shapes, no two exactly alike, yet extended observation has shown that they follow certain laws with absolute fidelity. The three great laws of crystals are : I". The Law of Constancy of Interfacial Angles. 2". The Law of Symmetry. 3"". The Law of Simple Mathematical Ratio. Law of Constancy of Interfacial Angles. Figs. i-6. A The variations between crystals of any one substance are limited by the following law : INTRODUCTORY. ■ 3 In all crystals of the same substance the angles between corre- sponding faces are constant* Figures i and 4 represent actual crystals of quartz. Figures 2 and 5 are sections of these in the direction of the plane of the paper which show that the angles between corresponding edges are equal. The same is shown by the horizontal sections, Figs. 3 and 6. Similarly in Fig. 7 the faces of the mag- Fig. 7. netite crystal are exactly parallel to those of /I l\ the ideal octahedron represented within it, f / I ^\ that is, such crystals of magnetite are / / j^kk. -'"\ bounded by faces which may or may not be 4-/--''^^r \ equal in size but in which the angle between ^^ •' / adjacent faces must be lOQ° 28' 16". nH / Law of Symmetry. In any crystal, faces and angles of the same kind are repeated with some degree of regularity. This regularity is called the symmetry of the crystal, and its law may be stated as follows : All crystals of any one substance are of the same grade of sym- metry. To understand this law certain definitions and explanations are essential. A crystal is symmetrical to the center when every straight line through the center encounters at equal distances on each side of the center two correspondingf points of the crystal. A crystal is symmetrical to an axis when if revolved about this axis the crystal reoccupies the same position in space, two, three, four, or six times during one complete revolution. That is, corre- sponding groups of planes exchange positions after revolutions of 180", 120°, 90° or 60°. The crystal of gypsum. Fig. 8, is symmetrical to the axis BB ; for, as shown in Fig. 9 both when the point a has moved to b or again to a the crystal occupies the original position in space. Moreover for any intermediate position of a such as c the space oc- * Steno in 1669 announced that in rock crystal there was no variation of angle in spite of the variation in relative size of the faces. Rom6 Delisle in 1783 measured and described over four hundred crystal forms and announced that in each species " the respective inclination of the faces to each other never varies." f For instance, the centers of similar edges or the intersections of similar lines, or the centres of similar faces or vertices of similar polyhedral angles. 4 ■ CR YSTALLOGRAPHY. cupied is distinctly not the same. That is, BB is an axis of two-fold or binary sym- metry. riG. 8. Fig. 9. The crystal of calcite, Fig. 10, has several axes of symmetry. Of these the vertical axis c is an axis of. threefold or trigonal symmetry for, as seen in horizontal projection. Fig. 10. Fig. II. Fig. 1 1 , when a has moved to ^ or to c or again to a, the crystal occupies the same po- sition in space. Fig. 12. Fig. 13. c > Fig. 14. ^E^ ::--=>-V; Fig 15. The line CC in the zircon crystal, Fig. 12, is an axis ol fourfold ox tetragonal sym- metry, for, as shown in the horizontal projection. Fig. 13, the crystal occupies the same INTRODUCTORY. 5 position in space when any point a has moved to b, c, d or again to a, and does not for any other position. Finally the line CC in the apatite crystal, Fig. 14, is an axis ol sixfold or hexagonal symmetry, because, as shown in horizontal projection, Fig. 15, the crystal occupies the same position in space when any point a has moved to b, c, d, e, f or again to a. A crystal is symmetrical to a plane when the plane so divides the crystal that either half is the mirrored reflection of the other, and 'every line perpendicular to the plane connects corresponding parts of the crystal and is bisected by the plane of symmetry. Thus in Fig. 16 the shaded plane so divides the crystal Fig. 16. 'hat a line from an angle b perpendicular to the plane passes through a corresponding angle a, or a perpendicular from c, the center of an edge, passes through d, the center of a sim- ilar edge. True Structural Symmetry. The true structural symmetry of a crystal is known only when all the characters have been considered. Structurally equivalent directions not only imply similar groupings of bounding faces but physical identity in all respects and two directions are not structurally equivalent if in these directions there is revealed any essential difference in behavior with polarized light or etching or pyro-electricity or with any other test, the results of which depend upon the manner the crystal molecules are built together. Classes of Symmetry. Theoretically there have been distinguished thirty-two classes of symmetry, that is, thirty-two varieties of regular molecular ar- rangement. The crystals corresponding to these classes differ in the number and relative position of their axes and planes of sym- metry, but all crystals of the same substance necessarily belong to the same class. By far the greater number of crystals of minerals belong to seven of the classes. Crystallographic Axes. The faces, or bounding planes, of crystals are most conveniently defined in position by the methods of Analytical Geometry. Three (in one system four) straight lines passing through the center of the crystal are chosen as crystallographic axes and any face CDE, CR YSTALLOGRAPHY. Fig. 1 7, is defined in position by its axial intercepts, that is by the distances OA, OB and OC along each axis from the center to the intersection with the plane ABC of which the face CDE is a part. The crystallographic axes are chosen to yield the simplest rela- tions, and are therefore always lines closely related to the symme- try, that is : axes of symmetry, lines normal ^'°- ■'7- to planes of symmetry, or where these are not to be had, lines parallel to at least two faces of the crystal. Interchangeable Axes. If the grouping of the faces about one axis is just the same as the grouping of the faces about another axis so that when the axes exchange positions the appearance of the crystal is not altered, the axes are said to be " interchangeable." It may be noted that if one crystallographic axis is also an axis of trigonal, tetragonal or hexagonal symmetry, the other crystal- lographic axes will be at right angles to it and interchangeable. The Six Systems of Crystallization. The thirty-two classes of syrnmetry may be united in the fol- lowing six systems by grouping together classes in which the crystallographic axes are similarly related : The Isometric System. — Three interchangeable axes at right angles to each other. The Tetragonal System. — Three axes at right angles, of which two are interchangeable. The Hexagonal System. — Four axes, three of which lie in one plane at sixty degrees to each other and are interchangeable, the fourth is at right angles to the other three. The Orthorhombic System. — Three axes at right angles but not interchangeable. The Monoclinic System. — Three non-interchangeable axes two of which are oblique to each other, the third is at right angles to the other two. The Triclinic System. — Three non-interchangeable axes at" oblique angles to each other. INTRODUCTORY. Determination of System. There will be exactly the same grouping of planes at the oppo- site " ends " of an axis and at the ends of interchangeable axes, that is these " ends " will lie in similar geometric parts. The crystal axes, as stated, p. 6, will be preferably axes of sym- metry or normals to planes of symmetry or at least parallel to two crystal faces. By viewing the crystal in different positions and noting the shape and recurrence of similar parts, it will be seen whether the line of sight is a satisfactory direction for an axis. With natural crystals not of ideal shape, Fig. i8. more practice is needed to recognize similar groupings of faces. A hand goniometer is of great assistance. For instance, the appearance of the sulphur crystal, Fig. l8, viewed in the direction AA is shown in Fig. 19. Evi- dently the line of sight {AA^ is an axis of symmetry for Fig. 19 /evolved 180° about A is unchanged in appearance. Moreover, the two lines through A, Fig. 19, are lines of symmetry, corresponding to planes of symmetry in Fig. 18, and suggest two other crystal axes normal to these planes. Fig. 19. Fig. 20. Fig. 21. When the crystal, Fig. 18, is viewed in the direction BB, Fig. 20, or of CC, Fig. 21, the axes suggested by Fig. 19 are confirmed. No other directions yield lines of symmetry hence the crystal axes are A A, BB and CC, Fig. 18, which are not inter- changeable and the system is orthorhombic. In crystals of the higher grades of symmetry inspection may show more possible crystal axes than are needed. Preference must then be given : {a) To directions at right angles to each other. , {b) To interchangeable directions. If only one direction is found normal to a plane of symmetry or itself an axis of symmetry this direction must be taken as one of the axes and the other two must be chosen each normal to the first and parallel to at least two faces. 8 CRYSTALLOGRAPHY. If no lines of symmetry are found the axes chosen should each be parallel to at least two faces. Crystal Forms. A crystal may be one crystal form or a combination of two or more forms. All faces of a crystal form must cut the crystal axes at the same relative distances from the center and there must be just enough faces to satisfy the symmetry of the crystal. If only two faces are required then these two constitute a "form." Ideal Crystal Forms in Drawings and Models. It is convenient, in elementary work, to make use of models and drawings of crystal forms in which all corresponding faces are equal in size and at equal distances from the center. Such a form may be said to be derived from the form in which a natural crystal occurs by moving each face parallel to itself until all corresponding faces are at an equal distance from the center. Thus in Fig. 7 the little inner octahedron is the ideal form of the outer actual form, and Fig. i is the ideal form of Fig. 4. Law of Simple Mathematical Ratio. Experience proves that a very exact law limits the number of different crystal forms which ever occur upon crystals of the same substance. This relation, which is variously known as :' " The Fundamental Law of Crystallography," " The Law of Simple Mathematical Ratio " and " The Law of Rational Indices," may be expressed as follows : In all crystals of the same chemical substance, if the intercepts of ANY face upon the crystallographic axes are divided* term by term, by the corresponding intercepts of any other face, the quotients will al- ways be simple rational numbers or infinity or zero. For example, if in a crystal of a given substance the axial in- tercepts are determined for one face to be relatively 0.813 : I : 1.903 then another face could occur in such a position that its in- tercepts in the same order would be relatively 1.626:1:5.709 1.626 5-709 because — ^ — = 2 and = 3, but a plane with intercepts rel- 0.813 1-903 -" ^ I' atively 1.734: I : 6.275 could not occur upon this crystal or upon any other crystal of this substance because — ^-^ — = 2.1328 -f- and *The intercepts are always reduced so that the corresponding term in each is unity. cor- INTRODUCTORY. 6.27s - — — = 3.2973 + that IS, the quotients obtained by dividing responding terms are not simple numbers or infinity. Crystal Habit. All crystals of the same substance must be bounded by faces belonging to one series of crystal forms connected by the funda- mental law. In theory any one form or all may occur bound- ing the same crystal ; or each crystal may show a different com- bination. In actual experience, however, the crystals of a substance if found at the same locality or formed in the same experiments show a well defined " habit," that is the same forms occur on all or nearly all of the crystals, and usually the same one or two forms so predominate as to constitute the greater portion of each crys- tal and the other occurring forms are present as relatively incon- spicuous faces or sometimes entirely absent. At another locality or from a change in laboratory conditions the crystals of this substance may show very different predomi- nating faces though necessarily faces of the same series. The Weiss Symbols and Parameters, To represent a crystal form a symbol must be equally satisfac- tory for all faces of the forn:i, and be quite independent of the ab- solute position of these faces so that it may be applicable to crystals of all sizes and to the most unequally devel- ^yn^^ oped forms. b/^ / ■ .--^^N. . If the intercepts are stated as a ratio d^^^^~~~^^ — Z^ then evidently these conditions are ful- V^K'''^ ^-^ filled. For the ratio OA:OB:OC, " XT /^ Fig. 22, not only represents the face y^^ ABC and (disregarding direction, of intercepts) the other faces A'B'C, etc., of the ideal form, but it represents equally well a parallel plane DEF in which OD : OE : 0F= OA:OB: OC. But a satisfactory symbol should also show the simple relation between the forms of the series. To accomplish this Professor Weiss denoted the axial intercepts of some selected and usually prominent form in each series by a, b and c corresponding respec- lo CRYSTALLOGRAPHY. tively to intercepts upon the axes AA, BB and CC oi Fig. 22 and wrote as the symbol of this selected unit face a:b:c. The symbol of any other face in the series was written in terms of a, b, and c and was necessarily such a symbol as 2a:b:c; a '. Zb: y^c or « : 00 b-.^c the coefficients or ^^' parameters being, because of the simple ;N mathematical ratio, always simple numbers, ;] \ simple fractions^ or infinity. (; \ To illustrate: l.et BCMN and DMN, ; \l \ Fig. 23, be two faces of a crystal. Pro- ;''''[^'-. '\ long BCMN to the axes, then are OA, OB ,'\mK '•, \ and 6'Cits axial intercepts and if this plane /'^^Uf^/jK ''■'"- is chosen as the unit plane then a:b:c=. /''/^'I P^^s. > ''.-... OA:OB:OC. /,-'*'•';':;-'---■" "^ Prolong DMN to the axes, then are *"'" OD, OF and OE the intercepts of DMN. Through one of the points D, E or F, for instance F, construct a . plane FHL parallel to the unit face, then also OH : OF : OL = a:b:c. If these faces obey the fundamental law, since one intercept of DMN and FHL is the same, the quotient of the others, that is, OD ^ OE -OH^""^ OL will be simple finite numbers or infinity. In the construction OD = \0H and OE = 2OL, hence if the symbol of BCNM is taken a.s a: b:c, that of DMN in comparison is \a:b : 2c or it could be written a: T^b : 6c or \a:^b -.c. When a face is parallel to an axis it is said to intersect it at an infinite distance and the sign 00 is used to express infinitj*. The Dana Symbols consist of the vertical parameter, a dash, and the other parameter. For instance 5« : (5 : -I c becomes |^ — 5 a: na : ma becomes tn — n. The Miller Indices may be obtained from Weiss's parameters by first dividing each by the common multiple of their numerators and taking the reciprocal of the result. That is t^a-.b-.kc be- comes a:\b:\c and the Miller's symbol is 153. When the symbol is enclosed in brackets ^.^•{1535, it is understood, to typify the form, but when in parentheses it signifies the individual face (153). INTRODUCTORY. ir Determination of Ideal Forms or Models by Inspection. After the axes have been chosen, as described p. 6, and placed in the conventional positions stated under each system, the de- termination of form and symbol may be conducted as follows : Place a straight edge (or pencil) in contact with a face and turn the straight edge always as a line in the face until its relation to each axis has been noted. The absolute values of the axial intercepts (from the center of crystal to where the straight edge intersects the axes) are not needed in determining the type of form ; all that is essential is to distinguish the greater intercept from the lesser or at most a very rough approximation to their relative lengths. If it is not evident that all the faces of the figure hold the same relation to the axes, any supposedly different face is tried in pre- cisely the same way with the straight edge and with respect to the same axes. In ideal crystals and models faces of the same form are equal in size and of the same shape. CHAPTER II. ISOMETRIC SYSTEM. The Isometric* system includes all crystal forms which can be referred to three interchangeable axes at right angles to each other. In models and drawings representing ideal forms these axes are €qual in length, but in actual crystals they are merely directions about which there are equal numbers of faces grouped with cor- responding faces at the same angles. The faces are not usually equal in size. The crystal or model is turned until one axis is vertical, one extends from left to right, and one from back to front. In stating the relative distances, from the center, at which any face cuts the three axes, the shortest distance is called a and the other distances, since the axes are interchangeable, are simple (or infinite) multiples of a. According to the number and arrangement of the planes and axes of symmetry, isometric crystals have been divided into five classes. A given substance can only occur in forms of one class. Three of the classes include nearly all known isometric minerals. In describing the forms of a class the most general form "the faces of which intersect the three axes at any distances permitted by the fundamental law" is first described and then the six limit forms corresponding to special positions of the faces of the general form. HEXOCTAHEDRAL CLASS. 32- No. I. Holohedral, Liebisch. No. I. Normal Group, Dana. Symmetry of the Class. The planes of symmetry are represented in Fig. 24 and the axes of symmetry in Fig. 25. The small black squares and triangles indicate axes of tetragonal and trigonal symmetry respectively- The tetragonal axes are chosen as the crystal axes. * Also called Tesseral, Tessular, Regular, Cubic and Monometric. ISOMETRIC SYSTEM. 13 Fig. 24. Fig. 25. The General Form or Hexoctahedron. Weiss, a:na:ma\ Dana, m— n\ Miller, \hkl\ . Composed of forty-eight faces each cutting the three axes in three different, but simply proportionate distances. In the ideal forms the faces are scalene triangles. Fig. 26. Fig. 27. Fig. 28. Fig. 26 shows the form a:\a:ia for which the diedral angles A, B, C, Fig. 27, are A= 158° 13'; B= 149°, C= 158° 13'; Fig. 27 shows « : 2a : 4« for which A = 162° 15'; ^ = 154° A7', C= 144° 3'- That the symmetry of the group requires forty-eight such faces to satisfy it may readily be proved by Fig. 28 which is simply an eighth (or octant) of Fig. 24 enlarged, being the center, OA, OB and OC the crystal axes and OX an axis of trigonal sym- metry. If any face I, with intercepts on OA, OB, OC respectively, l : 3 : | occurs, it must be accompanied by faces 2 and 3 because OX is an axis of trigonal symmetry, and the three white planes of symmetry make necessary planes 4, 5 and 6. Finally the entire octant must be reflected in each of the other" octants by the shaded planes of symmetry. The Limit Forms. The general form for special positions of the faces passes into limit forms. Six suppositions may be made each of which corre- H CR YSTALLO GRAPH Y. spends to a limit-form. Denoting infinity by oo in Weiss symbols and by i in Dana we have : Weiss. Dana. Miller. Each face parallel to two axes. 1 I. Cube. a 00 a : oca i — i { 1°°}- Each face parallel to one axis. 2. Dodecahedron. a ■.n:ai a I {ivo'f 3. Tetrahexahedron. a ■ na : (xa i — n A hko \ Each face intersects all axes. 4. Octahedron. a a : a I. ^"U 5. Trigonal Trisoctahedron. a a : ma m \hhi\ 6. Tetragonal TRibocTAHEDRON. a ma : ma ?!i — ■ m \ hkk\ The Six Limit Forms in Detail. I. The Cube. — a: 00 « : 00 « ; i — i\ \ioo\. Composed of six faces, Fig. 29, each parallel to two axes, all diedral and plane angles being right angles. The commonest of all crystal forms. In the ideal forms the faces are squares. Fig. 29. Fig. 30. 2. The Dodecahedron. — a: a: 00a; i ; {iio|. Composed of twelve faces, Fig. 30, each parallel to one axis and cutting the others at equal distances. In the ideal form each face is a rhombus. Angles between adjacent faces 120°, between alternate faces 90". The plane angles between edges are equal to the interfacial angles of the octahedron, i. e., 109° 28' 16" and 70° 31' 44". 3. Tetrahexahedron. — a -.na-.'^a; i— n\ \hko\. Composed of twenty -four faces, Fig. 31, each parallel to one axis Fig. 31. Fig. 32. ISOMETRIC SYSTEM. 15 and cutting the other two unequally in distances bearing a simple ratio to each other. In the ideal forms the faces are equal isos- celes triangles. Fig. 31 shows « : 2«: 00 « for which A = C= 143° 8'; Fig. 32 shows «: 3a: CO a for which A = 154" 9', C= 126° 52'. 4. The Octahedron. — a : a: a; i; |iii| Composed of eight faces, Fig. 33, each cutting the three axes at equal distances. In the ideal form the faces are equilateral tri- angles. The angles are 109° 28' 16" between adjacent faces and 70° 31' 44" between alternate faces. The alternate edges are at right angles and the adjacent edges at 60°. Fig. 33. Fig. 34. 5. Trigonal Tkisoctahedron. — a: a: ma; in; \hhl\. Composed of twenty-four faces, Fig. 34, each cutting two axes at equal distances, the third axes at some longer distance a simple multiple of the others. In the ideal forms the faces are isosceles triangles. For m = 2, A= 152° 44', B= 141° 3^'. For m = 3, ^ = 142° 8', ^=153° 28I'. 6. TeteagonalTrisoctahedron. — a -.ma -.ma; m — m; \hkk\. Composed of twenty-four faces, each cutting two axes equally and the third in some shorter distance bearing a simple ratio to the others. In the ideal form the faces are trapeziums. Fig. 35. Fig. 36. i6 CR YSTALLOGRAPHY. Fig. 35 shows a: 2a: 2.a for which A = 146° 27'; B= 131'' 59'. Fig. 36 shows « : 3« : 3« for which -(4 = 129" 31'; B = 144° 44'. Combinations in the Hexoctahedral Class. The most frequently occurring forms are the cube a, the octahedron /, the dodecahedron d, and the tetragonal trisoctahe- dron n = a : 2a : 2a. The other forms usually occur modifying these. Fig. 37. Fig. 38. Fig. 39. The cube a and dodecahedron d, Figs. 37, 38 are combined in crystals of fluorite, argentite and cuprite. The cube and octahe- FlG. 40. Fig. 41. Fig. 42. dron /, Figs. 39, 40 and 41, are very frequently combined in fluo- rite, pyrite, galenite, silver, sylvite and many other minerals. The Fig. 43. Fig. 44. Fig. 45. \ e \ 7 e e 4—11^ octahedron,/, and dodecahedron, d, Figs. 42 and 43, are frequently found in spinel, magnetite, franklinite and cuprite, while the three together, cube, dodecahedron, and octahedron. Fig. 44, occur in ISOMETRIC SYSTEM. 17 smaltite, galenite and fluorite. The tetfahexahedron e, {a : 2a : oad) is found with the cube in fluorite, Fig. 45. The tetragonal Fig. 46. Fig. 47. Fig. 48. - - -i*- - g trisoctahedron n, (a : 2a : 2a) is common in analcite, garnet and amalgam, either combined with the dodecahedron, Figs. 46 and 48, or with the cube. Fig. 47. Fig. 49. Fig. 50. Fig. si. Another tetragonal trisoctahedron o, (a : ^a : 3a) occurs in spinel and magnetite either with the octahedron, Fig. 49, or with both octahedron and dodecahedron, Figs. 50 and 51. Fig. 52. Fig. 53. Fig. 54. The trigonal trisoctahedron ;-, {a: a : 2d) occasionally occurs, .especially in galenite and magnetite, combined with octahedron and dodecahedrotl, Fig. 52."' The hexoctahedron t, [a: 2a: \a) occurs modifying cubes of fluorite. Fig. 53, and another hexocta- hedron s, {a:^a: 3a) occurs in garnet. Fig. 54. CR YSTALLOGRAPHY. HEXTETRAHEDRAL CLASS. 31. No. 2. Tetrahedral Hemihedry, Liebisch. No. 3. Tetrahedral Group, Dana-^ In this class of isometric forms, to which crystals of the dia- mond, tetrahedrite, sphalerite and boracite belong, the shaded planes of Fig. 24 are no longer planes of symmetry, and the sym- metry is restricted to the diagonal planes shown in Fig. 55 and to the axes formed by their intersection. The General Form or Hextetrahedron. Weiss, a:na: nia ; Dana, m — n ; Miller l^ hkl [> . Composed of twenty-four faces each cutting the three axes in three different, but simply proportionate, distances. In the ideal forms the faces are scalene triangles. Fig. 55. Fig. 56. Fig. 57. In a manner precisely similar to that followed on p. 13 it may be shown that if one face of the general form occurs twenty-four must, and according to the position of the first face the form will be that shown in Fig, 56, usually called the positive form, or that shown in Fig. 57, called the negative form. The positions of the crystallographic axes are indicated. The Limit Forms. Three of the six limit forms are geometrically identical with the forms of the preceding class, namely, 1. The Cube. Fig. 29. 2. The Dodecahedron. Fig. 30. 3. The Tetrahexahedron. Figs. 31 and 32. The geometrically new forms are : 4. The Tetrahedron. — a: a: a; i; \\i\\. Composed of four faces. Fig. 58, each cutting the three axes at equal distances. In the ideal form the faces are equilateral triangles. All interfacial angles are 70° 31' 44" and all plane angles be- tween edges are 60° ISOMETRIC SYSTEM. 19 S. Tetr^onal Tristetrahedron. — a: a -.ma; m; \hhl\. Composed of twelve faces, Fig. 59, each cutting two axes equally and the third in some longer distance a simple multiple of the others. In the ideal form the faces are trapeziums. Fig. 58. Fig. 59. Fig. 60. 6. Trigonal Tristetrahedron. — a:ma:ma; m — m; \hkk\. Composed of twelve faces, Fig. 60, each cutting two axes equally and the third in some shorter distance bearing a simple ratio to the others. In the ideal form the faces are isosceles triangles. Combinations in the Hextetrahedral Class. The characteristics of the crystals of this group are best shown Fig. 61. Fig. 62. Fig. 63. in the combination forms, since the simple forms are comparatively rare and the predominating form is frequently the cube. Fig. 64. Fig. 65. Fig. 66. ^ The simple tetrahedron /, Fig. 61, and the combination of the positive and negative tetrahedrons, Fig. 62, occur as crystals of sphal- 20 CR YSTALLOGRAPHY. erite and tetrahedrite. The combination of the tetrahedron and cube a, Fig. 63 and 64, is common in boracite and pharmacosiderite. The tetrahedron with the dodecahedron d, Fig. 65, occurs in tetrahedrite, and with both cube and dodecahedron, Fig. 66, in boracite. Fig. 67. Fig. 68. Fig. 69. Figs. 67, 68, 69 and 70 are all crystals of tetrahedrite. Fig. 67 is the tetrahedron with the trigonal tristetrahedron n, {a: la: 2d). In Fig. 68 the negative form of n occurs and- in Fig. 69 the dodecahedron d is an additional form. Fig. 70. Fig. 71. Fig. 72. Fig. 70 is more complex and includes the dodecahedron d, the tetragonal tristetrahedron r, {a: a: 2d) and the trigonal tristetra- hedrons o, (a : 3a : 3a) and n, {a: 2a: 2d). Fig 71 represents a crystal of boracite with the cube, dodecahedron, both tetrahedrons and the trigonal tristetrahedron n, while Fig. 72 shows the hextetrahedron s, {a : ^a : -2,0) combined with the cube and tetra- hexahedron g, {a : -|« : oo«). CLASS OF THE DIPLOID. 30. No. 4. Pentagonal Hemihedry, Liebisch. No. 2. Pyritohedral Group, Dana. Ciystals of the common mineral pyrite and of the minerals cobaltite and smaltite have the symmetry shown in Fig. 73. ISOMETRIC SYSTEM. 21 The General Form or Diploid. Weiss, a:na:ma; Dana, m-n; Miller, a ; i — n\ \hko\. Composed of twelve faces, Fig. ^6, each parallel to one axis and cutting the other two unequally in distances bearing a simple ratio to each other. In the ideal forms the faces are pentagons. Combinations in the Class of the Diploid. These combinations greatly resemble those of the hexoctahedral class because five of the seven forms occur in both, and the other two are parallel faced. 22 Fig. 77. CR YSTALLOGRAPHY. Fig. 78. Fig. 79. Fig. "]"] shows the pyritohedron e,{a:2a: 00 a) with the cube a. Figs. 78 and 79 show the same form with the octahedron p. Fig. 80. Fig. 81. Fig. 82. Fig. 80 shows the three forms combined. Fig. 81 shows the same pyritohedron e and octahedron / combined with the diploid s, {a : ^a : 2,0) and Fig. 82 shows this diploid with the cube and oc- tahedron. Two classes of lower symmetry exist but need not be described here as no common minerals are known to occur in one and the minerals referred to the other are so referred rather by virtue of etching tests than from the shape of the common crystals. CHAPTER III. TETRAGONAL SYSTEM. Inall Tetragonal* forms the crystallographic axes can be chosen at right angles to each other, so that two will be interchange- able. In models and drawings representing ideal forms the inter- changeable axes are equal in length and the third axes is longer or shorter but never a simple multiple of the lengths of the inter- changeable axes. In real crystals the interchangeable axes are directions surrounded by exactly the same number of faces and with corresponding faces at the same angles. The grouping of faces about the third axis is not the same as to angles and not necessarily the same as to number of faces. Conventionally the crystal is placed so that the two inter- changeable axes are horizontal and the third axis vertical. The former are known as the basal or a axes, the latter as the vertical or c axis. Groups or Classes of Forms. According to the number and arrangement of the planes and axes of symmetry, tetragonal crystal forms have been divided into seven classes. Of these two are unknown among crystals of min- erals and two are represented by one mineral each. The remain- ing classes are described following the same general method as in the isometric. Series. Just as in the isometric system a substance can onlj'^ occur in forms of one class and in forms of one series in that class. This has been explained generally upon page 8, but warrants here a more detailed explanation. In the isometric system all three axes were interchangeable, that is, all were surrounded by the same number of faces at the same * Also called Pyramidal, Viergliedrige, Zwei-und-einaxige, Monodimetric, Quadiatic and Diraetric. 24 CRYSTALLOGRAPHY. angles, and these angles were always such that the three intercepts of any face were simple multiples of each other, such as a : 2« : 3«. In the tetragonal system, however, while the intercepts of any face upon the two interchangeable axes are simple multiples of each other, the intercept of this face with the third axis will not be a simple multiple of either of the other intercepts and furthermore this complex relation will be different/^/- every form upon each dif- ferent substance. Experience, however; has shown that a perfectly exact relation exists between the different complex values for the third inter- cept obtained from different faces of the same substance such that this intercept for any one face is always a simple multiple or simple fractional part of the corresponding intercept for any other face. Advantage is taken of this to secure simple instead of complex symbols as follows : Some prominent face which must intersect the vertical and at least one of the basal axes is chosen as the unit face, and its symbol is said to be a : na : c in which a is the shorter horizontal intercept, c is the vertical intercept and n is necessarily a simple number or infinite. This ratio is always reduced imtil a is unity, that is, may be of such a form as « : «« : c = 1:2: 1.073. If now the intercepts of any other face of a crystal of the same substance are obtained and reduced so that the shorter horizontal intercept is unity, the face may be expressed by the symbol a : n'a : mc in which both m and n' are simple numbers or infinite. For example, by calculation the relative intercepts" of the com- mon forms of zircon, see Figs. 91 to 94, p. 27, are/ = i : i : 0.64 which may be denoted hy a:a:c, then in comparison the face m with intercepts 1:1:00 is «:a:ooc; the face a with intercepts I : 00 : 00 is a: oo« : oor ; the face u with intercepts 1:1: 1.92 is a:a:y and the face x with intercepts 1:3: 1.92 is a : 3« : 3c. CLASS OF THE DITETRAGONAL PYRAMID. 15. No. 18. Holohedry, Liebisch. No. 6. Normal, Dana. Symmetry of the Class. As shown in Fig. 83 forms in this class are symmetrical to one horizontal plane and to four vertical planes at forty-five degrees to each other. The intersections of these planes with each other are axes of symmetry and of these CC is an axis of tetragonal sym- metry. CC and either pair of alternate horizontal axes may be chosen as crystal axes. TETRAGONAL SYSTEM. 25 The General Form or Ditetragonal Pyramid. Weiss, a:na:mc; Dana, m- n; Miller, { hkl \ . Composed of sixteen faces, Fig. 84, each cutting the two basal axes at unequal but simply proportionate distances, and the ver- tical axis at a distance not simply proportionate to the other dis- tances. In the ideal forms the faces are scalene triangles. Fig. 83. Fig. 84. The values of m and n may be determined from any two diedral angles. For Xand Fthe equations are : I + cos i Fx 1. 4142 cos ^ X ' n cot |- X= sin «, tan « = mc. That sixteen such faces are needed to satisfy the symmetry is seen in Fig. 83. If the face I occurs, the planes of symmetry make necessary the occurrence of faces 2, 3, and 4, and each of these must have on each side and below a corresponding plane and so on ; or sixteen faces in all. Limit Forms. The general form, for special positions of the faces, passes into limit forms. Assuming the conventional position of the axes with the axis c vertical these limit positions are : Each face horizontal. Weiss. Dana. Miller I. Basal Pinacoid. 00 a : 00 ^ : ^ \ 001 j- Each face vertical. 2. Prism of Sfxond Order. a (XI a :iX3 c i — i { i°o|- 3. Prism of First Order. a : a -.oo c t {iio[- 4. Ditetragonal Prism. a na •,'X c i — n \hko\ Each face inclined. 5. Pyramid of Second Order. a ■.IX a -.mc in — i \hol\ 6. Pyramid of First Order. a ' a : mc m \hhl\ 26 CR YSTALLOGRAPHY. The Limit Forms in Detail. 1. Basal Pinacoid. — oo«:oo«:c: o, fooi}. Composed of two faces, Fig. 85, each parallel to both the basal axes. 2. Prism of Second Order. — a : 00 « : 00 ^ ; i — i ; {ioo\. Composed of four faces, Fig. 86, each parallel to the vertical axis and to one basal axis. The interfacial angles are 90°. Fig. 85. Fig. 86. Fig. 87. 3. Prism of the First Order. — a : a: ^ c\ I ; \\ \o\. Composed of four faces, Fig. 87, each parallel to the vertical axis and cutting the basal axes at equal distances from the centre. The interfacial angles are 90°. 4. DiTETRAGONAL Prism. — a : na : CO c ] i— n; \hko]. Composed of eight faces. Fig. 88, each parallel to the vertical axis and cutting the two basal axes in distances unequal but sim- ply proportionate. Fig. 88. Fig. 89. Fig. 90. The value of « may be determined. Fig. 88, by the equations : « = tan ^ X, or n = tan (135° — J K) TETRAGONAL SYSTEM. 27 5. Pyramid of Second Order. — a-.ooa-.mc; m — i; \hol\. Composed of eight faces, Fig. 89, each parallel to one basal axis, and cutting the other basal axis and the vertical axis at either unit distances or simple multiples of these. In ideal forms the faces are isosceles triangles. The value of mc may be determined by the following equations, Fig. 89 : cos ^Fx 1.4142 = sin a, tun ^ Z = tun a, mc = tana. 6. Pyramid of First Order. — a:a:inc\ m; \hhl\. Composed of eight faces, Fig. 90, each cutting the basal axes at equal distances, and the vertical axis at some distance not a simple multiple of the basal intercepts. In the ideal forms the faces will be isosceles triangles. The value of ntc may be determined, Fig. 90, by the following equations : nu = tan \ Z x -JOJi, or sin a = cot \ X, mc — tan a. Series and Combinations in the Class of Ditetragonal Pyramid. It is only by considering the forms in series, that is the forms of each substance separately, that a clear idea is obtained as to the pyramidal forms. The prismatic forms and the basal pinacoid are alike for all substances crystallizing in the class, but the pyra- mids vary in shape and angle with the relative lengths of mc and a. Though as explained, p. 24, the pyramids which occur upon crystals of any one substance are definitely related in axial inter- cepts and usually very limited in number. The common forms of certain minerals in this class have there- fore been assembled here. Fig. 91. Fig. 92. Fig. 93. ^"^f^ ^^ Fig. 94. 28 CR YSTALLOGRAPHY. Zircon. — Axes a -.c ^ I : 0.640. Fig. 91 shows the common association of unit pyramid / and unit prism m. In Fig. 92 these two forms are combined with the prism of the second order a and in Fig. 93 with the pyramid u = (a -.a: 2,c). Fig. 94 shows the union of second order prism, unit pyramid and ditetragonal pyramid x = (a-.^a: y). Fig. 95. ^~ Fig. 96. a'' I '"^ Fig. 97. Vesuvianite. — Axes a:c^= i : 0.537. The unit pyramid in vesuvianite is a httle flatter than in zircon but not much, hence in the drawings there is little apparent differ- ence between the pyramid angles in Fig. 91 and Fig. 97. The relative development of faces, or crystal habit, is, however, mark- edly different, as is at once apparent on comparing the two series of common crystals. Fig. 95 shows the combination of unit pyramid/, unit prism-** and basal pinacoid c. Fig. 96 shows these three forms combined with the prism of the second order a and Fig. 97 shows the two prisms and the unit pyramid. Fig. 98. Fig. 100. Fig. ioi. Fig. 99. Apophyllite. — Axes a:c= i : 1.252. TETRAGONAL SYSTEM. 29 As indicated by the ratios of a to c the unit pyramid of this mineral is much more acute than in zircon and vesuvianite, this is clearly apparent in Fig. 10 1. The figures also illustrate very well the possibility of great differences in habit without any difference in occurring forms, thus Figs. 98, 99 and 100 are all combinations the unitpyramid/, basal pinacoid c and second order prism a. In Fig. 10 1 the basal pinacoid does not occur. Fig. 103. Fig. 102. / I ^ \ /a \ VT'- Cassiterite. — Axes « : c = i : 0.6723. In this the ratio of « to c is closely as in zircon but the common association is now the unit pyramid / with the second order pyra- mid d zs shown in Fig. 102. In Fig. T03 these forms occur with a ditetragonal pyramid z = (a : ^ a : ^c) and the unit prism 7n. CLASS OF THE THIRD ORDER PYRAMID. 13. No. 21 — Pyramidal Hemihedry, Liebisch. No. 8 — Pyramidal Group, Dana. Certain crystals of the minerals scheelite and wernerite are sym- metrical to one horizontal plane and one vertical tetragonal axis only. Fig. 104. Fig. 105. Fig. 106. 30 CR YSTALLOGRAPHY. The General Form or Third Order Pyramid. — Weiss, a:na:mc\ Dana, m — n; Miller, \kkl\. Composed of eight faces, Fig. 105, each cutting the two basal axes at unequal but simply proportionate distances, and the ver- tical axis at a distance not simply proportionate to the other dis- tances. In the ideal forms the faces are isosceles triangles. That eight such faces satisfy the symmetry is shown by Fig. 104. Any occurring face must, because of the vertical axis of tetragonal symmetry, occur with three other faces above the horizontal axes, and because of the horizontal plane of symmetry each of these must be accompanied by a face below the plane. The Limit Forms. Five of the limit forms are geometrically like forms already described, namely : 1. Basal Pinacoid. Fig. 85. 2. Prism of Second Order. Fig. 86. 3. Prism of First Order. Fig. 87. 5. Pyramid of Second Order. Fig. 89. 6. Pyramid of the First Order. Fig. 90. The geometrically new form is : 4. Prism of Third Order. — a:na: c ; I ; [lolo]. Composed of six faces, Fig. 120, each parallel to the vertical axis and to one basal axis and cutting the other two basal axes at equal distances. Fig. 119. Fig. 120. Fig. 121. 3. Hexag. Prism of Second Order. — 2a : 2a : a : oac ; i— 2 ; {II20|. Composed of six faces, Fig. 121, each parallel to the vertical axis and cutting one basal axis at a certain distance and the other two at twice that distance. n a : a : 00c ; i — « ; } hklo \ . 4. DiHEXAGONAL PrISM. HU : Fig. 122. 3 I y Composed of twelve faces. Fig. 122, each parallel to the vertical axes and cutting all three basal axes at unequal distances which are simple multiples of each other. The value of n may be calculated by the following equations. Fig. 122. tan^Xx .5773 = 1.732 = n 2 — n' n + I n — \ or tan \y y. 5. Hexag. Pyramid of First Order. — a : ixa : mc ; m ; \hohi]. Composed of twelve faces, Fig. 123, each parallel to one basal axis, cutting the other two basal axes at equal distances, and 36 CR YSTALLOGRAPHY. cutting the vertical axis at some distance not simple proportionate to the intercepts on the basal axes. In ideal forms the faces are isosceles triangles. The value of mc may be found by the following equations, Fig. 123. tan \Z X .866 = mc ; or sin a = cot \X x 1.732 ; tan a = mc. Fig. 123. Fig. 124. 6. Hexag. Pyramid of Second Order. — 2« ■.2a:a:mc;m— 2; [hfn'ki]. Composed of twelve faces, Fig. 1 24, each cutting one basal axis at a certain distance, the other basal axes at twice that distance, and the vertical axis at some distance not simply proportionate to the others. In the ideal form the faces are isosceles triangles. ^The value of mc may be calculated, Fig. 124, by the equations : 2 cos \X ^ sin ^Z ; tan ^Z = mc. Combinations of Forms in the Class of Dihexagonal Pyramid. Beryl. — Axes « : t = i : 0.499 Fig. 125. Fig. 126. Fig. 127. Fig. 125 shows the usual prism of first order in and basal pina- coid c ; in Fig. 126 the second order pyramid e = (2a : 2a:a:2c) occurs and in Fig. 1 27 the unit pyramid / is also present. HEXAGONAL SYSTEM. Z7 CLASS OF THE THIRD ORDER PYRAMID. 25. No. 9. Pyramidal Hemihedry, Liebisch. No. 15. Pyramidal Group, Dana. Crystals of the minerals apatite and vanadinite are symmetrical only to one horizontal plane and one verticalhexagonal axis. Fig. 128. Fig. 129. Fig. 130. The General Form or Third Order Pyramid. — Weiss, n na: n — I a: a: mc ; Dana, m — n ; Miller, \hkli\ Composed of twelve faces, Fig. 129, each intersecting the vertical axis and also cutting all three basal axes at unequal distances which are simple multiples of each other. That twelve such faces are necessary to satisfy the symmetry of the class, may be traced in Fig. 128. The resulting form is geometrically like the pyramids of first and second order, and is distinguishable only when combined with other forms. The Lfimit Forms. Five of the limit forms are geometrically like forms already de- scribed, namely ; 1. Basal PiNACoiD. Fig. 119. 2. Hexagonal Prism of First Order. Fig. 120. 3. Hexagonal Prism OF Second Order. Fig. 121. 5. Hexagonal Pyramid of First Order. Fig. 123. 6. Hexagonal Pyramid OF Second Order. Fig. 124. The new form is : n 4. Hexagonal Prism of Third Order. — na : « : a : 00 t ; ^ n— 1 ' i—n; ^ hkJo \ . Composed of six faces, Fig. 1 30, each parallel to the vertical axis and cutting all three basal axes at unequal distances which are simple multiples of each other. 38 CR YSTALLOGRAPHY. Combinations in the Class of the Third Order Pyramid. Apatite. — Axes a:c = \: 0.734. As in the corresponding tetragonal class it is only the occasional crystal that shows the symmetry by the position of its faces. Thus in the six figured crystals of apatite only Fig. 163 proves the true symmetry by the occurring faces. Fig. 131. Fig- 132- Fig- 133- — . \ FlG. 134- fY~-- ff ' -if- W. ; U-----_: 1 -«- 1 Fig. 135. Fig. 136. Figs. 131, 132, 133 and 134 show variations in habit in com- binations of the unit pyramid /, basal pinacoid c and first and second order prisms, m and a. In Fig. 135 a flatter pyramid o = (a : 00 « : a : i c) occurs with the basal pinacoid and second order prism, and in Fig. 1 36 a third order pyramid ^ = {^a:\a:a: ifi) occurs with the unit prism, basal pinacoid, pyramid of first order o and pyramid of second order e = (2a ■.2a -.a: 2c). Vanadinite. — Axes a : c =■ i : 0.7 1 2. The usual combination, Fig. 137, is the prism m and base c, but Fig. 137. Fig. 138. M \JkJ in Fig. 138, there is shown also the unit pyramid p, and a third order pyramid v, {^a : ^ a : a: 3c). HEXAGONAL SYSTEM. 39 SCALENOHEDRAL CLASS. 31. No. 13. Rhombohedral Heraihedry, LieUsch. No. 19. Rhombohedral Group, Dana. This is by far the most important group in the hexagonal sys- tem, and- includes the crystals of such minerals as calcite, corun- dum, hematite and chabazite. Symmetry of the Class. Fig. 1 39 shows the three planes of symmetry at sixty degrees with the three axes diagonal to these and one vertical axis. The axes of symmetry are taken as the crystal axes. The General Form or Scalenohedron. Weiss, na : - a:a:mc; Dan3i,m — n: Miller, ]M/i]. Composed of twelve faces, Fig. 140, each cutting all the axes. In the ideal form the faces are scalene triangles. The ad- jacent polar edges are necessarily unequal. Fig. 139. Fig. 140. To satisfy the symmetry any face, I, Fig. 139, must be accompanied by a face 2, because of a plane of symmetry, and by a face 3, because OA is an axis of symmetry, and these require others and so on to twelve faces. The Limit Forms. Four of the limit forms have been described, namely : 1. Basal PiNACoiD, Fig. 119. 3. Hexagonal Prism of Second Order, Fig. 121. 4. Dihexagonal Prism, Fig. 122. 6. Hexagonal Pyramid of Second Order, Fig. 1 24. The new forms are : 2. Trigonal Prism of First Order. — a : cc a -.a: 00 c ; / ; {1010;. Composed of three vertical faces, Fig. 141, each of which is parallel to one basal axis and intersects the others at equal dis- tances from the center. Fig. 141. 40 CRYSTALLOGRAPHY. Fig. 141. Fig. 142. Rhombohedron of the First Order. — a : 00 « : a:mc;m; \hohi\. Composed of six faces, Fig. 142, each cutting two basal axes at equal distances, parallel to the third and cutting the vertical. In the ideal forms the faces are rhombs. The values of mc may be calculated by the following equations. Fig. 142: sin a=^ cos X x 1.155 ; tan a x .866 =^ mc. Combinations in the Scalenohedral Class. Calcite. — Axes a: c=^ \: 0.854. Figs. 143 to 150 represent the more common of the extremely numerous combinations shown by crystals of calcite. Rhombo- hedrons and scalenohedrons predominate. The rhombohedrons Fig. 143. Fig. 144. Fig. 145. HEXAGONAL SYSTEM. 41 shown are/ the unit, Fig. 143, ^ the negative form of « : 00 « ; a : ^c, Fig. 144 ; /the negative form of a : oa a : a : 2c, Fig. 148 ; and g the positive form of a: 00 a: a: i6c, Fig. 145. Two scalenohedrons only are shown, v =^a : ^a: a : ^c, Fig. 147, and w = ^a : 4a : a : ^c, Fig. 1 50. The rhombohedron e occurs more frequently than the unit and is shown in combination with the rhombohedron q in Fig. 145 and with the prism jn in 149. The unit rhombohedron is shown in combination with the sca- lenohedron v in Fig. 147, and with the two scalenohedrons v and w in Fig. 150. Figs. 149. Fig. 150. Hematite. — Axes a:c^ i : 1.365. Fig. 1 5 1 shows the unit rhombohedron / with the basal pina- coid c and the second order pyramid n = {2a : 2a : a: |-c). Fig. 153 shows the same except that the basal pinacoid is replaced by the rhombohedron^ = {a : 00a : a : ^f), and Fig. 152 shows the two rhombohedrons / and g. Fig. 151. Fig. 152. Fig. 153. Corundum. — Axes a:c= i : 1.363. The unit forms of hematite and corundum are practically iden- tical, but the combinations and habits are very different. Fig. 1 54 shows a second order pyramid n = (2a •.2a; a: ^c). Fig. i 5 5 shows this and two other second order forms o = {2a ■.2a: a: ^c) and a = (2a : 2a : a : 00 c) and a rhombohedron/" =(« : oo« : a : 2c). Fig. 1 56 shows a second order pyramid w = {2a •.2a: a: 2c) with the unit rhombohedron / and the basal pinacoid c. 42 CRYSTALLOGRAPHY. Fig. 154. Fig. 155 Fig. 156. Chabazite. — Axes « :c= i : 1.086. Fig. 157 shows the unit rhombohedron / and Fig. 158 shows this combined with the more acute and more obtuse rhombohedrons e = {a: 00a : a:^c) and/ = {a -.caa-.a: 2c). Fig. 1 59 shows a twin of the variety phacolite. Fig. 157. Fig. 158. Fig. 159. HEMIMORPHIC CLASS 20. No. 14. Second Hemimorphic Tetartohedry, Liebisch. No. 20. Rhombohedral Hemimorphic Group, Dana. The common mineral, tourmahne, and the ruby silvers, proust- ite and pyrargyrite, occur in forms showing different group- FlG. 160. Fig. 161. ings of faces at opposite ends of the vertical axis. That is the forms are without horizontal planes or axes of symmetry, Fig. 160. HEXAGONAL SYSTEM. 43 The General Form or Hemimorphic Ditrigonal Pyramid. Weiss, na : — a -.a: mc ; Dana, m — n ; Miller, \hkli\ n — I Composed of six faces, Fig. i6i, each cutting all basal axes at simply related distances and all cutting the vertical axis on the same side of the center. As seen in Fig. l6o if one such face occurs five others must to satisfy the symmetry. The Limit Forms. Only two of the forms have been described. 2. Trigonal Prism First Order, Fig. 141. 3. Hexagonal Prism Second Order, Fig. 121. The geometrically new forms are : I. The Basal Plane, za a: ca a : o^ a:c : o; {0001 1. Composed of one face parallel to the basal axes. n a: a: ^ c ; t — n; \hklo\. 4. Ditrigonal Prism. n — I Composed of six faces, Fig. 162, each parallel to the vertical axis and cutting all three basal axes at unequal distances which are simple multiples of each other. Fig. 162. Fig. 163. Fig. 164. 5. Hemimorphic Trigonal Pyramid of First Order. a : cx)a:a: mc ; m ; \ hohi\ . Composed of three faces, Fig. 163, each parallel to one basal axis cutting the other two basal axes at equal distances, and cut- ting the vertical axis at some distance no( simply proportionate to the intercepts on the basal axes. 6. Hemimorphic Hexagonal Pyramid of Second Order. 2a : 2a : a : mc ; m — 2; \hh2hi\. Composed of six faces, Fig. 164, each cutting one basal axis at a certain distance, the other basal axes at twice that distance, and 44 CR YSTALLOGRAPHY. the vertical axis at some distance not simply proportionate to the others. Combinations in the Hemimorphic Class. Tourmaline. — Axes a\c^\ : 0.447. Fig. 165 shows the first order trigonal prism m, the second order hexagonal prism a ; at the upper end the trigonal pyramids of first order p =(a: oa a: a:c) and/ = (a : 00 a : a : 2c) , but at the lower end the trigonal pyramid/ only. Fig. 166 shows m, p and a, but does not so evidently reveal the hemimorphic symmetry. Fig. 167 again shows m and a central, with at one end p and at the other /. Fig. 165. Fig. 166. Fig. 167. TRAPEZOHEDRAL CLASS. 18. No. 15. Trapezohedral Tetartohedry, Liebisch. No. 22. Trapezohedral Group, ZJowa. Crystals of the common mineral quarj:z are without planes of symmetry but are symmetrical to the four axes shown in Fig. 168. The General Form or Trigonal Trapezohedron. n Weiss, na : — — - a:a:mc; Dana, m-n; Miller, \ hkli' \ . Composed of six faces. Fig. 168, each cutting all the axes. In ideal forms these are trapeziums. Fig. 168. Fig. 169. Since OC, Fig. 168, is an axis of trigonal symmetry, a face I of the general form must be accompanied by faces 2 and 3, and because the other axes, as O^, are axes of binary symmetry, each of these must be accompanied by one of the faces 4, 5 and 6. HEXAGONAL SYSTEM. 45 The Limit Forms. Five of the six forms have been described namely : 1. Basal Pinacoid, Fig. 119. 2. Hkxagonal Prism of First Order, Fig. 1 20. 3. Hexagonal Prism of Second Order, Fig. 121. 4. Ditrigonal Prism, Fig. 162. 5. Rhombohedron of First Order, Fig. 142. The geometrical new form is 6. Trigonal Pyramid of Second Order. — 2a: 2a -.a: mc ; m—2; -j kh2ki J> . Composed of six faces, Fig. 1 69, each cutting two basal axes at an equal distance, the third at half that distance and the vertical somewhere. The faces in the ideal form are isosceles triangles, and a horizontal section is an equilateral triangle. Combinations in the Trapezohedral Class. Quartz. — Axes^a : c = i : 1.099. Fig. 1 70 shows the positive p and negative p unit rhombohe- drons, combined in equal proportions. Figs. 172, 173 and 174 Fig. 170. Fig. 171. Fig. 172. Fig. 174. Fig. 175. Fig. 176. show one or both of these combined with the hexagonal prism of first order m. 46 CRYSTALLOGRAPHY. In Fig. 171a second order pyramid s = (2a : 2a: a: 2c), necessa- rily trigonal, occurs with the forms previously mentioned. Fig. 175 and 176 both show the prism m and the two unit rhombohe- drons, but in Fig. 175 the second order trigonal pyramid s and the trigonal trapezohedron x = (^a :6a: a: 6c) are both to the right of the positive rhombohedron p, while in Fig. 176 they are to the left. These crystals are called right-handed and left-handed, and represent a structural difference which is also revealed by etching, rotation of the plane of polarization and pyro-electric phenomena. CLASS OF THIRD ORDER RHOMBOHEDRON. 17. No. 16. Rhombohedral Tetartohedry, Liebisch. No. 21. Trirhombohedral Group, Dana. A number of minerals, ilmenite, dolomite, phenacite, dioptase, willemite, etc., occur in forms which are symmetrical only to a vertical trigonal axis, and to the central point. The General Form or Rhombohedron of JThird Order. ft Weiss, na : « :a:mc: Dana, m-n: Miller, \ hkli \ . Composed of six faces, Fig. 178, each cutting all the axes at unequal distances. Any face. Fig. 177, must, because of the trigonal axis, be accompanied by two other faces 2 and 3 and each of the three must have a diametrically opposite face, 4, 5 or 6, as in Fig. 177. Fig 177. Fig. 178. The Limit Forms. Of the six limit forms, five have been described, namely : 1. Basal Pinacoid, Fig. 119. 2. Hexagonal Prism of First Order, Fig. 1 20. 3. Hexagonal Prism of Second Order, Fig. 121. 4. Hexagonal Prism of Third Order, Fig. 130. 5. Rhombohedron of First Order, Fig. 142. The geometrically new form is : Fig. 179. HEXAGONAL SYSTEM. 47 6. Rhombohedron of Second Order. 2a: 2a: a: mc ; m-2; \ hh2hi \ . Composed of six faces, Fig. 179,. each cutting two basal axes at twice the distance that it cuts the third, and cutting the vertical somewhere. Combinations in the Class of the Third Order Rhombohe- dron. Phenacite. — Axes a:c ^=\ : 0.66107. Fig. 180. Fig. 181. Fig. 180 shows the first order prism m and second order prism a and the third order rhombohedron x = ^ a: ^a : a:^c. Fig. 1 8 1 shows first order rhombohedrons r, z and d, second order rhombohedrons p and o, third order rhombohedrons x and s and second order prism a. CHAPTER V. ORTKORHOMBIC SYSTEM. The orthorhombic* system includes three classes of symmetry, in all of which the crystallographic axes may be chosen at right angles to each other, but are not interchangeable. Series. All forms which ever occur upon crystals of the same substance belong to one series. That is, their faces occur at such angles that if the intercepts of any one face are reduced until one term is unity, then the axial intercepts of any other face, taken in the same order and reduced until the same term is unity, will be simple or infinite multiples term for term of those of the first face. If one of the faces is taken as the unit and its intercepts ex- pressed by a:b:c all other faces may be simply expressed in terms of this face. For instance in the crystals of topaz, Figs. 197 to 1 99, the calculated intercepts for certain faces and their symbols, when / is taken as the unit face, are as follows : Face. - Calculated Intercepts. Symbol in Terms of/. P 0.528 : I : 0.477 a: b \c i 0.528 : I : 0.318 a:b:%c ? 0.528 : I : 0.954 a -.b ■.■2c in 0.528 : I : 00 a : b: ooc I 1. 156 : I : 00 la :b \ 00 f 00: I : 0.954 003 : /5 : 2(r h I : 00:0.318 a : rxb : y^c The Choice of the Unit Plane. The directions of the axes having been determined, the unit plane chosen will if possible be a face of frequent occurrence which intersects all the axes.f The orientation is then optional. One axis, Fig. 182, will be made the vertical, or c, axis, the other two * Also called Prismatic, Rhombic, Ein-und-einaxige, Anisometric and Trimetric. f On account of similarity of crystals to some species of related composition, another choice may be made or the values a, b and c may result from two different faces or from cleavages, because of greater brilliancy and more accurate measurements. ORTHORHOMBIC SYSTEM. 49 will be horizontal, and the horizontal axis with the longer unit intercept will be placed to run from left to right, and called the macro or b axis ; the other axis will run from front to back and will be called the brachy or S. axis. PYRAMIDAL CLASS 8. No. 25. Holohedry, Liebisch. No. 25. Normal Group, Dana. Almost all orthorhombic minerals crystallize in forms sym- metrical to three planes at right angles to each other, as in Fig. 182, the intersections of these being axes of binary symmetry and chosen as the crystallographic axes. General Form or Pyramid. Composed'of eight faces. Figs. 183 and 184, each of which cuts the three axes in the same relative distances ; these intercepts are never simple multiples of each other, but in crystals of the same sub- stance are necessarily simple multiples of the corresponding inter- cepts of the selected unit pyramid. In the ideal forms the faces are equal scalene triangles. Fig. 182. Fig. 183. Fig. 184. The values of nS. and mc may be determined from any two of the angles X, Y, Z, Fig. 184,' by equations like the following : cos « = cos \X sin^|z ' cos \Z cos /9 = 2— sin J A'' na = cot a. mc = tan /9 x nd. Evidently a rhombic pyramid may be composed either of faces with the unit intercepts, or the faces may be at other angles. 50 CRYSTALLOGRAPHY. with any one or two of the intercepts simple multiples of the unit intercepts. Three types are distinguished, the symbols being :* Weiss. Unit series Pyramids, a:h:mc Macro Pyramids, d : nb\ mc Brachy Pyramids, iia:b: mc Dana. m m — n in — « MlLI.ER. { hhl\ \ hkl \ \ khl \ Limit Forms. The general form for special positions of the faces may be- come one of six limit forms, as follows : Each face parallel to two axes. Weiss. Dana. 00 d : (xib : c o a : (X b : oii c i — i 1. Basal Pinacoid. 2. Macro Pinacoid. 3. Brachy Pinacoid. 00 Each face parallel to one axis. 4. Brachy Dome. 00 a : b-.mc 5. Macro Dome. a: oob\mc d : nb : ca c n d:b : ca c 6. Prism. d: b : (xi c i — i ni — I in — i i — n i — n Miller. \ 001 \ { 100 t- Macro Prism, a : ?ib : ixi c i - n d :b:c) and z = ( ood -.b-.^c) and the macro dome t = d: : mc; —m — l; \ hol )■ . Fig. 213. Fig. 214 \ ! \ \ i \ 6. Prism. Composed of four faces, Fig. 214, each parallel to the vertical axis, and cutting the basal axes in distances not simply propor- tionate. As in the pyramids, a prism compared with the chosen unit plane may be : Unit Prism a -.d 00c I -. — - a smp Combinations Prismatic Class. Pyroxene. — Axes d:b:c= 1.092 : i : 0.589 ; /3 = 74° 10' 9". Fig. 2 1 5 shows the three pinacoids, a, b and c, the unit prism m, MO NO CLINIC SYSTEM. 59 the negative unit hemi-pyramid / and the positive hemi-pyramid v = (a : 3 : 2c). Fig. 2 1 7 is the same without v and Fig. 216 omits also the basal pinacoid c. Fig. 2 1 8 shows the unit prism m, the basal Fig. 216. Fig. 217. Fig. pinacoid c, two positive hemi-pyramids v and w = (a:b : y) and a clino dome .s = ( 00 « : ^ : 2c). Amphibole. — Axes« -.'b: c = 0.551; i : 0.293; ^ = 73° S^'V- Fig. 219. Fig. 220. Fig. 221. ^■^ Fig. 2 1 9 shows the unit prisjn m, the basal and clino pinacoids, c and b and the positive unit hemi pyramid /. Fig. 220 shows the unit prism, clino pinacoid and unit clino dome d = (^ca a: b : c). Fig. 221 shows the same except that the clino pinacoid b is re- placed by the ortho pinacoid a. Fig. 222. Fig. 223 Fig. 224. Fig. 225. ^<^itv 6o CRYSTALLOGRAPHY. Orthoclase. — Axes « :^: (r=o.658; i :o.555; ^=6^" 56' 46". Fig. 222 shows the unit prism m, clino and basal pinacoids ^ and c, and positive hemi orthodome 7 = (a: 00 ^: 2c). In Fig. 223 J is replaced hy o = (a: co d : c), and in Fig. 225 the clino pinacoid is omitted. Fig. 224 includes the forms of 257 and also a clino prism s = ^a : d : ca c and the unit pyramid p. Not one of the common monocHnic minerals is known to crystallize in either of the other two classes possible in the system. CHAPTER VII. TRICLINIC SYSTEM.* The Triclinic System has been divided into two classes in both of which the crystallographic axes are three hnes obhque to each other and not interchangeable. The three axes, Fig. 226, ^'°- "^■ are usually chosen parallel to prominent edges of the crystal. Oneof the three chosen axes ■ is placed in a vertical position, and is called the vertical axis, j c. Of the others, the brachy a axis & takes the position of the clino axis in the monoclinic system and the macro axis b takes its position according to its angles with d and c. The oblique angles between the axes are conventionally desig- nated by Greek letters as follows : d t\ bhy y; d f\ c hy ^ ; b /\ c hy a. Series. As in the preceding systems all the "forms " in which one sub- stance ever crystaUizes belong to the same series, that is, if referred to three axes inclined at certain constant values for a, ^ and Y, the intercepts of any two faces reduced until the same term in each is unity, and the corresponding terms divided the one by the other ; the quotients will be either simple numbers, simple frac- tions, or infinity. PINACOIDAL CLASS. 2. No. 31. Holohedry, Liebisch. No. 31. Normal Class, Dana. All known triclinic minerals crystallize in forms symmetrical to the center only. Every form must therefore consist of two faces. •Also known as Tetarto prismatic, Ein-und-eingliedrige, Triclinohedral, Clinorhom- toidal, Anorthic, Doubly oblique and Asymmetric. 62 CR YSTALLOGRAPHY. Miller. \ hhl \ \ hhl \ { hhl \ General Form or Tetrapyramid. Composed of two opposite faces, Fig. 227, which may be, as in the orthorhombic, unit, macro or brachy. Weiss. Dana. Unit Series, a:b:mc m Macro, d:nb: mc m — n Brachy, nd-.b : mc in — « According to the position of the faces with reference to the axes, names and symbols may be given. Thus, for four tetra- pyramids of the unit series : Upper Right Tetra-Pyramid, Upper Left Tetra-Pyramid, Lower Right Tetra-Pyramid, Lower Left Tetra-Pyramid, Fig. 227. a b : mc ;«' \ hhl} a b' : mc 'm { hhl ). a' : b' : mc m, iMiy^r] a> ■.b:mc pn {hhl}^ Fig. 228. /fS /^ --6 ,...J;-X*' a 1 ■ -'-"'J^ ,^''\ / ,^::^ — " Limit Forms. The general form for certain positions of the faces will pass into limit forms as follows : Weiss. Dana 00a : oab : c o d : ic d' : oab : mc d :nb : 00c m — /' Miller. { 001 ;. i 100 y i 010 ;. { okl \ \ hoi \ \ hho \ TRI CLINIC SYSTEM. 63 2. Macro PiNAcoiD. — ^: 00^ :00c; i—i; ^ 100 [>. Composed of two faces parallel to the macro and vertical axes. The faces a of Figs. 228, 232, 233 and 234. 3. Brachy PiNACOiD. — CK,a:b: cac; i-l ; .j 010)^. Composed of two faces, each parallel to the brachy and vertical axes. The faces b of Figs. 228, 232, and 233. 4. Hemi Brachy Dosies. Composed of two faces, Fig. 229, parallel to a and intersecting b and c in distances not simply related. According to the position the form may be : Right upper, co a-.h Left upper, 00 a : b' mc mc { okl\ { okl\ Fig. 229. Fig. 230. Fig. 231. 5. Hemi Macro Dome. Composed of two faces. Fig. 230, each parallel to the macro axis and cutting the brachy axis and the vertical axis in distances not simply proportionate. According to position the form may be : Upper front, d: J kho ^ Left Brachy, nd : b' : 00c t-'n ^ kko y Combinations in the Triclinic System. Fig. 232 shows a crystal of chalcanthite with brachy pinacoid b, macro pinacoid a, right hemi prism w, left hemi prism M and lower 64 CR YSTALLOGRAPHY. left tetra pyramid /. Fig. 233 shows a crystal of cyanite with the three pinacoids a, b and c, the right m, and left M hemi unit prisms and a right hemi brachy prism l={2a : b : cx>c). Fig. 232. Fig. 233 Fig. 234. M \ \r k^ — -"K m N \y> \ 6 m h ir ';/ I . a 1 I Fig. 234 shows a crystal of axinite with both hemi prisms m and M, macro pinacoid a, upper right and upperjeft unit pyramids /' and '/ and a macro dome e = cl : cab : 2c. CHAPTER VIII. TWINNED CRYSTALS. Crystals frequently occur in which the faces, while evidently belonging to more than one individual, possess a very definite position with respect to each other, usually symmetrical to a defi- nite plane called a twinning plane. Such a symmetrical intergrowth of two like crystals is called a twinned crystal. When the two individuals penetrate each other they constitute a penetration twin and when they do not they con- stitute a contact twin. Twinning Plane. The twinning plane, since it is a plane of symmetry for the pair of crystals, cannot be a plane of symmetry for either individually. It is usually, however, parallel to a crystal face of simple symbol. Twin Axis. The line normal to the twinning plane is called the tiviji axis and usually the two individuals are in the relative positions corre- sponding to a half revolution about this line of one of two originally parallel individuals. Evidently this twin axis cannot be an axis of binary symmetry, p. 4, because a rotation of 180° about it would bring the crystals into an identical instead of a reversed position. For the same reason the twin axis cannot be an axis of tetragonal or hexagonal symmetry, though it could be an axis of trigonal symmetry. The twin axis will usually, however, be either a crys- tallographic axis or normal to some very prominent face. ISOMETRIC TWINS. Twinning Plane an Octahedron Face. The most frequent type is with the twinning plane an octahedral face. Fig. 235 shows an octahedron with the twinning plane shaded and the twin axis AA normal thereto ; Fig. 237 shows the corres- ponding contact twin, and Fig. 236 the interpenetrating twin. Fig. 238 shows a combination of cube and octahedron, the twin plane shaded and the twin axis AA normal thereto. Fig. 239 66 CR YSTALLOGRAPHY. shows two such crystals united in reversed positions. Fig. 240 shows two cubes interpenetrating. Fig. 235. Fig. 2-;6. Fig. 237. Fig. 238. Fig. 239. Fig. 240. Twinning PlaJie a Cube Face. A cube face can be a twinning plane in the class of the hex- tetrahedron, p. 18. Fig. 241 shows the tetrahedron with the twinning plane shaded and the twin axis OA normal thereto. Fig. 242 shows the pene- tration twin, the reversed tetrahedron being shaded. Fig. Fig. 242. Twinning Plane a Dodecahedron Face. A face of the dodecahedron can be a twinning plane in the class of the diploid. Fig. 243 shows a pyritohedron with twinning plane shaded and twin axis OA normal thereto. Fig. 244 shows the penetration twin, the reversed form being shaded. TWINNED CRYSTALS. 67 Fig. 243. Fig. 244. TETRAGONAL TWINS. Twinning Plane a Face of Second Order Pyramid. This is the most common type. Fig. 245 shows a cassiterite crystal with such a plane shaded. Fig. 246 shows the contact Fig. 245. Fig. 246. Fig. 247. twin, the reversed form being shaded. Fig. 247 shows a similar contact twin of rutile. Fig. 248 shows the pyramid of hausman- nite with twinning plane shaded. Fig. 249 shows a contact twin Fig. 248. Fig. 249. Fig. 250. and Fig. 250 shows four pyramids which have grown about a fifth in normal position, each of the pyramids with a twinning plane parallel to a different face of the second order pyramid. 68 CRYSTALL OGRAPHY. Other planes may be twinning planes. Chalcopyrite occurs with twinning plane parallel to a first order pyramid face. In scheelite, Fig. 251, the twinning plane is parallel to a face of the second order prism. Fig. 251. HEXAGONAL TWIN. Twins are rare in the class of highest sym- metry of this system. In the scalenohedral class twins occur with the twinning plane par- allel to a rhombohedron or base but not to a prism face. In quartz, however, which belongs to the trapezohedral class, p. 44, without planes of symmetry, the twinning plane is frequently a prism face. Twinning Plane a Face of a Rhombohedron. Fig. 252, represents a calcite unit rhombohedron with a twin- EiG. 252. Fig ning plane parallel to a: ) If stony or vitreous, treat a small sharp-edged fragment in the platinum forceps, at the tip of the blue flame, directing the flame upon the point. (<:) If in powder, or with a tendency to crumble, grind and mix with water to fine paste, spread thin on coal and dry, and, if cohe- rent, hold in the forceps. If not coherent dip a moistened platinum wire in the powder, and treat the adhering powder in the flame. There will be noted both the degree of fusibility and manner of fusion. The degree of fusibility is stated in much the same way as the hardness by comparing it with a scale of fusibility. It is gener- ally, however, sufficient to class a mineral as simply easily fusible, fusible, difficultly fusible, or infusible. For purposes of compari- son, the following scale, suggested by v. Kobell, is usually adopted : 1. Stibnitc, coarse splinters fuse in a candle flame. 2. Natrolitc, fine splinters fuse in a candle flame. 3. Garnet [Ahnandite), coarse splinters easily fuse before the blowpipe. ' 4. Actinolite, coarse splinters fuse less readily before the blow- pipe. 5. Orthoclase, only fused in fine splinters or on thin edges before the blowpipe. 6. Calamine, finest edge only rounded in hottest part of flame. 7. Quartz, infusible, retaining the edge in all its sharpness. OPERATIONS OF BLOWPIPE ANALYSIS. 91 The trial should always be made on small and fine pointed frag- ments. Penfield recommends using a standard size about i mm. in diameter and 4 mm. long. The fragment should project beyond the platinum as in Fig. 300, so that heat may not be drawn off ^'"- 3°°- by the platinum, and the flame directed especially upon the point. It is always well to examine the splinter with a magnifying glass, before and after heating, to aid the eye in determining whether the edges have or have not been rounded by the heat. The manner of fusion may be such as to result in a glass or slag which is clear and transparent, or white and opaque, or of some color, or filled with bubbles. There may be a frothing or intu- mescence, or a swelling and splitting (exfoliation). In certain in- stances the color and form may change without fusion, etc. Flame Coloration. During the fusion test the non-luminous veil is sometimes un- changed, but it is often enlarged and colored by some volatilizing ■ constituent. There is frequently a bright yellow coloration due to sodium salts, but this gives place to the color proper. The flame is best seen in a dark room or against a black back- ground, such as a piece of charcoal, and is often improved by hydrochloric acid and occasionally by other reagents. Some elements color the flame best at a gentle heat, others onh- at the highest heat attainable. A good method to cover all cases is to dip the end of a flattened platinum vvire first in hydrochloric acid and then in the finely powdered substance and hold it first in the mantle flame near the wick and then at the hottest portion at the tip of the blue flame. It is possible in this way to obtain two distinct flames such as the red of calcium and the blue from cop- per chloride. The colors can also often be seen to decided advantage by simply holding the wire in the non-luminous flame of a Bunseti burner or even in the flame of an alcohol lamp. Flame tests for Ca, Sr and Ba are not usually obtainable from silicates. 92 BLOWPIPE ANALYSIS. The important flame colorations are : Yellows. Yellow. — Sodium and all its salts. Invisible with blue glass. Reds. Carmine. — Lithium compounds. Masked by soda flame. Vio- let through blue glass. Invisible through green glass. Scarlet. — Strontium compounds. Masked by barium flame Violet red through blue glass. Yellowish through green glass. Yellowish. — Calcium compounds. Masked by barium flame. Greenish gray through blue glass. Green through green glass. Greens. Yellowi.sh. — Barium compounds, molybdenum sulphide and oxide ; borates especially with sulphuric acid or boracic acid flux. Pure Green. — Compounds of tellurium or thallium. Emerald. — Most copper compounds without hydrochloric acid. Bluish. — Phosphoric acid and phosphates with sulphuric acid. Feeble. — Antimony compounds. Ammonium compounds. Whitish. — Zinc. Blues. Light. — Arsenic, lead and selenium. Azure. — Copper chloride. With Green. — Copper bromide and other copper compounds with hydrochloric acid. Violet. Potassium compounds. Obscured by soda flame. Purple red through blue glass. Bluish green through green glass. In sili- cates improved by mixing the powdered substance with an equal volume of powdered gypsum. USE OF THE SPECTROSCOPE. When salts of the same metal are volatilized in the non-luminous flame of a Bunsen burner the spectra producedT)n decomposing the resultant light by a prism will show lines identical in color, number and relative position. Salts of different metals will yield different lines. Although, with pure salts, the already described flame color- ations are generally distinct and conclusive, it will frequently hap- pen that in silicates or minerals containing two or more reacting OPFRATIONS OF BLOWPIPE ANALYSIS. 93 Fig 301. substances the eye alone will fail to identify the flame coloration. It is well therefore to supplement the ordinary flame tests by spectroscopic observation. In the blowpipe laboratory the chief Hse of the spectroscope will be to identify the metals of the potas- sium and calcium families singly or in mixtures. For this purpose the direct vision spectroscope of Hoff- man, Fig. 301, is perhaps the most convenient. The substance under examination should be moistened with hydro- chloric acid and brought on a plati- num wire into the non-luminous flame of the Bunsen burner as in the ordi- nary flame test. In viewing the flame through the properly adjusted spec- troscope certain bright lines will be seen, and by comparing these with the chart, Fig. 304, or with substances of known composition, the nature of the substance may be determined. The sodium line will almost invariably be present and the position of the other lines will be best fixed by their situation relative to this bright yellow line. The more ordinary form of spectroscope. Fig. 302, has special advantages in allowing an easy comparison of flames. /I is the Fig. 302. observation telescope, B the collimator through which the light from the flames M and M ' is sent as parallel rays through the prism Pto the telescope A. The third telescope C sends the image of 94 BLOWPIPE ANALYSIS. Fig. 303. a micrometer scale to A by which the relative distance apart of the lines is judged. Fig. 302 shows an enlarged view of the collimator B. By means of the little rect- angular prism i the light from a second flame H placed at one side is sent through the colli- mator and its spectrum obtained side by side with that from the flame G. In this manner the spectrum of an unknown substance may be compared with that of one of known composition and if hnes Fig. 304. -red org. yellow gre eii red _; orange yellow green Y Tiulet viulet OPERATIONS OF BLOWPIPE ANALYSIS. 95 of the unkno\Yn coincide with those of the known substance the identity of at least one of its constituents is established. The chart (Fig. 304) and brief description of spectra of substances giving distinct lines with the Bunsen flame will be of service. Potassium — two red lines and one violet line. Sodium — a single bright yellow line, which with higher dispersion is resolved into two lines. Almost always present from the small amounts of sodium in dust. Lithium — one very bright deep red line and a faint line in the orange. Strontium — a number of characteristic red lines and one blue line. Calcium — a bright red, and a bright green line, with fainter red to yellow lines and a line in the violet. Barium — a number of yellow and green lines. Rubidium — two violet and two red lines with several less prom- inent lines in the orange, yellow and green. CiESiuM — two distinct blue lines and one orange line. Thallium — one characteristic green line. Indium — an indigo blue line and a violet line. Volatilization. In blowpipe analysis, antimony, arsenic, cadmium, zinc, tin, lead, mercury and bismuth are always determined by securing sublimates of either the metals themselves or of some volatile oxide, iodide, etc. Other elements and compounds, such as sulphur, selenium, tel- lurium, osmium, molybedenum, ammonia, etc., are also volatilized and in part determined during volatilization as odors or by sub- limates. Certain other compounds, particularly chlorides of sodium and potassium and of some other metals, such as copper, tin and lead, yield sublimates ordinarily disregarded. Volatilization tests are commonly obtained on charcoal, or plaster or in open and closed tubes. Treatment on Charcoal. A shallow cavity, just sufficient to prevent the substance sHp- ping, is bored at one end of the charcoal and a small fragment or a very little of the powdered substance is placed in it. The char- 96 BLOWPIPE ANALYSIS. coal is held in the left hand, so that the surface is .at right angles to the lamp but tipped vertically at about 1 20° to the direction in which the flame is blown. A gentle oxidizing flame is blown, the blue flame not touching the substance, but being just behind and in a line with it. After a Fig. 305. few moments the test is examined and all changes are noted, such as position and color of sublimates, color changes, odors, decrepi- tation, deflagration, formation of metal globules or magnetic parti- cles. The heat is then increased and continued as long as the same reactions occur, but if, for instance, a sublimate of new color or position is obtained, it is often well to remove the first subli- mate either by transferring the substance to another piece of char- coal or by brushing away the first formed sublimate after its satis- factory identification. The same steps should then be followed using the reducing flame. The sublimates differ in color and position on the charcoal ; some are easily removed by heating with the oxidizing flame, some by the reducing flame, some are almost non-volatile, and some im- part colors to the flame. Treatment on Plaster Tablets. Experience has shown that the sublimates obtained on charcoal and plaster supplement each other. The method of using is pre- cisely the same, and white sublimates are easily examined by first smoking the plaster surface by holding it in the lamp flame. The coatings differ in position, and to some extent in color. OPERATIONS OF BLOWPIPE ANALYSIS.- 97 Plaster is the better conductor, condenses the oxides closer to the assay, and therefore, the more volatile coatings are thicker and more noticeable on plaster, while the less volatile coatings are more noticeable when spread out on charcoal. Charcoal supple- ments the reducing action of the flame, and therefore is the better support where strong reduction is desired. Comparison of Important Sublimates on Charcoal and Plaster.* I. Without Fluxes.— Treated First in O. F., then in R. F, Arsenic. — White volatile coat. On smoked plaster it is crystal- line and prominent ; on charcoal it is fainter and less distinct, but the odor of garlic is more marked. Deposits at some distance from assay. Fumes invisible close to assay. Antimony. — White pulverulent volatile coat, more prominent on charcoal. Deposits near assay and fumes are visible close to assay after removal of flame. Selenium. On Charcoal. — Horse-radish odor and a steel-gray coat. On Plaster. — Horse-radish odor, brick-red to crimson coat. Tellurium. On Charcoal. — White coat with red or yellow border. On Plaster. — Deep brown coat. Cadmium. On Charcoal. — Brown coat surrounded by peacock tarnish. On Plaster. — Dark brown coat shading to greenish-yellow and again to dark brown. Molybdenum. — Crystalline yellow and white coat with an outer circle of ultramarine blue. Most satisfactory on plaster. Lead. — 1 Yellow sublimate with outer fringe of white. More Bismuth. — j noticeable on charcoal than on plaster. Zinc. — White, not easily volatile coat, yellow while hot. Best on charcoal. Tin. — White non-volatile coat close to assay, yellowish while hot. Best on charcoal. * Certain compounds give white coating before the blowpipe which at times cause confusion. Notably among these are many chlorides and the sulphate of lead. Among minerals, galena and other lead sulphides give a white sublimate which must not be confused with arsenic or antimony coats. 98 BLOWPIPE ANALYSTS. II. With Bismuth Flux * Lead. On Plaster. — Chrome yellow coat. On Charcoal. — Greenish-yellow, equally voluminous coat. Bismuth. On Plaster. — Chocolate-brown coat, with an underlying scar- let; with ammonia it becomes orange-yellow, and later cherry-red. On Charcoal. — Bright red band with a fringe of yellow. Mercury. On Plaster. — Scarlet coat with yellow, but if quickly heated is dull yellow and black. On Charcoal. — Faint yellow coat. Antimony. On Plaster. — Orange coat stippled with peach-red. On Charcoal. — Faint yellow coat. Arsenic. On Plaster. — Yellow and orange coat, and not usually satis- factory. On Charcoal. — Faint yellow coat. Tin. On Plaster. — Brownish-orange coat. On Charcoal. — White coat. The following tests show only on the plaster : Selenium. — Reddish-brown, nearly scarlet. Tellurium. — Purplish-brown with darker border. Molybdenum. — Deep ultramarine blue. III. With Soda (Sodium Carbonate or Bicarbonate). Soda on charcoal exerts a reducing action partly by the forma- tion of sodium cyanide, partly because the salts sink into the char- coal and yield gaseous sodium and carbon monoxide. The most satisfactory method is to mix the substance with three parts of the moistened reagent and a little borax ; then spread on the char- coal and treat with a good reducing flame until everything that can be absorbed has disappeared. Moisten the charcoal with water, break out and grind the portion containing the charge. Wash away the lighter part and examine the residue for scales and magnetic particles. * Two parts of sulphur, one part of potassium iodide, one part of acid potassium sulphate. OPERATIONS OF BLOWPIPE ANALYSIS. 99 The reduction may result in : 1 . Coating, but no reduced metal. Volatile white coating and garlic odor, . . . As. Reddish-brown and orange coating with characteristic variegated border, ...... Cd. Non-volatile coating, yellow hot and white cold, . . Zn. Volatile steel-gray coating and horseradish odor, . Se. Volatile white coating with reddish border, . . Te. 2. Coating with reduced inetal. Volatile thick white coating and gray brittle button, . Sb, Lemon-yellow coating and reddish-white brittle button, Bi. Sulphur-yellow coating and gray malleable button, . Pb. Non-volatile white coating, yellow hot, and malleable white button, ....... Sn. White coating, made blue by touch of R. F., and gray infusible particles, ...... Mo. 3. Reduced metal only. Malleable buttons, . . . . Cu, Ag, Au. Gray magnetic particles, , . . Fe, Co, Ni. Gray non-magnetic infusible particles, W^, Pt, Pd, Ir, Rh. The carbonate combines with many substances forming both fusible and infusible compounds. Many silicates dissolve with a little of the reagent, but with more are infusible ; a few elements form colored beads with the reagent, especially on platinum. The residue left after heating may contain malleable metallic beads of copper, lead, silver, tin or gold. It may consist of a brittle easily fusible button of bismuth, antimony, or the sulphide, arsenide or antimonide of some metal. It may be magnetic from the presence of iron, cobalt or nickel or it may show an alkaline reaction, when touched to moistened red litmus or turmeric paper, indicating the presence of some member of the potassium or cal- cium group of metals. Infusible Compounds. — Mg, Al, Zr, Th, Y, Gl. Fusible Compounds. — Si02 effervesces and forms a clear bead that remains clear on cooling if the reagent is not in excess. TiOj effervesces and forms a clear yellow bead, crystalline and opaque on cooling : WO3 and M0O3 effervesce but sink in the charcoal. Ba, Sr, Ta, V, Nb sink into the charcoal. Ca fuses, then decomposes, and the soda sinks into the charcoal. loo BLOWPIPE ANALYSIS. Colored Beads. — Mn forms a turquois or blue-green opaque bead with soda on plantinum wire in oxidizing flame. Cr forms a chrome-yellow opaque bead with soda on platinum wire in oxidizing flame, which becomes green in reducing flame. Sulphur Reaction. — If a little of the residue, with some of the charcoal beneath, is taken up upon the point of a knife and placed upon a wet silver coin, the coin will be blackened if sulphur was present as a sulphide. Sulphates and other sulphur compounds will also give the same reaction after thorough fusion. The test should always be made on a fresh piece of charcoal. IV. With Metallic Sodium. Reducing effects which are obtained with soda only by hard blowing may be accomplished by the use of metallic sodium im- mediately and with the greatest ease. The metal should be handled carefully and not allowed to come in contact with water. It should be kept in small tightly closed bottles, and if kept cov- ered with naphtha, vfhich is not necessary, care should be taken that the the naphtha is not exposed to fire. A piece of sodium about the size of an ordinaiy borax bead is cut off with a knife and hammered out flat. The powdered substance is placed upon the sodium, pressed into it and the whole moulded into a little ball with a knife blade. This sodium ball should not be touched with the fingers, for if some oxides are present, such as lead oxide, spontaneous combustion may take place. After placing the sodium ball on the charcoal it should be touched care- fully with a match or with the Bunsen flame. A little flash ensues and the reduction is accomplished. The residue can now be safely heated with the reducing flame of the blowpipe, any reduced metal collected together and the sodium compounds volatilized or ab- sorbed by the charcoal. When present in sufficient quantity, beads of the malleable metals can be obtained immediately from almost any of their mineral compounds ; metals like zinc and tin which require reduction before volatilization yield their sublimates with comparative ease ; and if a little of the charcoal beneath the assay is placed on a wet silver coin the sulphur reaction will be obtained if sulphur was present. In general the results are the same as outlined for soda but are much more easily secured. Even silica, silicates, borates, etc., are reduced but are generally identified by other means. OPERATIONS OF BLOWPIPE ANALYSIS. loi These reactions are not successful on plaster tablets on account of their non-absorbent character. Tests in Closed Tubes and Matrasses. The matrass is practically a glass tube closed at one end and blown to a bulb. In most cases better results are secured by using a plain narrow tube about 4 inches by ^ inch and closed at one end. The usual purpose is to note the effects of heat without essential oxidation ; they are also used for effecting fusions with Fig. 306. such reagents as KHSO^ or KCIO3. Enough of the substance is slid down a narrow strip of paper, previously in- serted in the tube, to fill it to the height of about one-half inch ; the paper is with- drawn and the slightly inclined tiibe heated at the lower end gradually to a red heat. Fig. 306. The results may be : evolution of water, odorous and non- odorous vapors, sublimates of various colors, decrepitation, phosphorescence, fusion, charring, change of color, magnetization, etc. Acid or alkaline moisture in the upper part of tube, . Odorless gas that assists combustion (nitrates, chlorates and per oxides), ...... Pungent gas that whitens lime water, . . . . Odors. Odor of prussic aid, ....... Odor of putrid eggs, ..... Odor that suffocates, fumes colorless, bleaching action, Odor that suffocates, fumes violet, . fumes brown, . fumes greenish yellow, . fumes etch the glass. Odor of nitric peroxide, fumes reddish-brown, Odor of ammonia, fumes colorless or white, . H,0. 0. CO3. CN. H,S y SO, I.* Br. CI, F. NO, NH3 •t *I, Br, CI, F and NjOj are assisted by mixing substance with acid potassium sulphate. t NHj, Hg, As, Cd are assisted by mixing with soda. 102 BLOWPIPE ANALYSIS. Sublimates. Sublimate white, fusing yellow fusing to drops, disagreeable odor, and volatile, . yellow hot, infusible, yellow hot, fusible, fusible, needle crystals, volatile, octahedral crystals, fusible, amorphous powder, Sublimate mirror-like, collects in globules, does not collect in globules, . Sublimate red when hot, yellow cold. Sublimate dark red when hot, reddish-yellow cold, . Sublimate black when hot, reddish-brown cold. Sublimate black, but becomes red when rubbed, Sublimate red to black, but becomes red when rubbed, ....... Color of substances changes from white to yellow, cools yellow, . from white to yellow, cools white, . from white to dark yellow, cools light yellow, . from white to brown, cools yellow, . from white to brown, cools brown, . from yellow or red to darker, after strong heat, cools green, ...... from red to black, cools red, .... from blue or green to black, cools black. PbCl,. Os. NH, (salts). HgCl. HgCl,. Sb,03. As,03. TeO,. Hg. As, Cd,Te. S. As,S3. Sb.S,. HgS. Se. PbO. ZnO. Bi,03. SnO,. CdO. Cr.O,. Fe.O,. CuO. Tests in Open Glass Tubes. Fig. 307. By using a somewhat longer tube, open at both ends and held in an inclined position, a current of air is made to pass over the heated substance, and thus many substances not vola- tile in themselves absorb oxy- gen and release volatile oxides. The substance should be in state of powder. Place the assay near the lower OPERATIONS OF BLOWPIPE ANALYSIS. 103 end of the tube and heat gently, Fig. 307, creasing the air current by holding the tube vertical. Odor that suffocates, bleaching action, Odor of rotten horseradish, Odor of garlic, ...... Sublimate white volatile octahedral crystals, Sublimate white partially volatile, fusible to yellow drops, pearl gray cold. Sublimate white non-volatile powder, dense fumes, ...... Sublimate white non-volatile powder, fu- sible to colorless drops. Sublimate white non-volatile powder, fusi- ble to yellow drops, white when cold. Sublimate white non-volatile fusible powder, ...... Sublimate gray, red at distance, Sublimate yellow hot, white cold, crystal- line near the assay, blue in reducing flame, ...... Sublimate brown hot, yellow cold, fusible, SubHmate metallic mirror. and then strongly, in- more and more nearly SO2, in SeO„ As,03, As,03, dicating S. Se. " As. " As. PbOCl, u PbCl,. SbA. n Sb. Te0„ ii Te. PbSO,, u PbS. BiSO,, Se0„ a It BiS. Se. M0O3, Bi,03, n il it Mo. Bi. Hg. Bead Tests with Borax and with Salt of Phosphorus. Preliminary to bead tests, many compounds, sulphides, arsenides, arsenates, etc., maybe converted into oxides by roasting as follows : Treat in a shallow cavity on charcoal at a dull red heat, never allowing the substance to fuse or even sinter. Use a feeble oxidiz- ing flame to drive off sulphur, then a feeble reducing flame to reduce arsenical compounds, then reheat in an oxidizing flame. Turn, crush, and reroast until no sulphurous or garlic odor is noticeable. Sodium tetraborate or borax may be considered as made up of sodium metaborate and boron trioxide. The boron trioxide at a high temperature combines with metallic oxides, driving out volatile acids, and by the a d, of the oxidizing flame the resulting borates fuse with the sodium metaborate to form double borates often of a characteristic color. The color may differ when hot and cold and according to degree of oxidation and reduction. I04 BLOWPIPE ANALYSIS. Sodium ammonium phosphate, or salt of phosphorus, by fusion loses water and ammonia and becomes sodium metaphosphate. The sodium metaphosphate at high temperatures combines with metallic oxides to form double phosphates and pyrophosphates, which like the double borates are frequently colored, although the colors often differ from those obtained with borax. A bead of either flux is made on platinum wire as described on page 88, and the substance is added gradually to the warm bead and fused with it in the oxidizing flame. The ease of dissolving, effer- vescence, color, change of color, etc., should be noted. We may greatly simplify the tabulation of results by the follow- ing division : 1. Oxides which Color neither Borax or Salt of Phosphorus, or at Most Impart a Pale Yellow to the Hot Bead when Added in Large Amounts. Oxides of Noticeable Distinctions. Aluminum. — Cannot be flamed opaque. Antimony. — Yellow hot in oxidizing flame, flamed opaque gray in reducing flame, on charcoal with tin black. Expelled by reducing flame in time. Barium. — Flamed opaque white. Bismuth. — Like antiriiony. Cadmium. — Like antimony, but not made black by fusion with tin. Calcium. — Like barium. Lead. — Like antimony, but not made black by fusion with tin. Magnesium. — Like barium. Silicon. — Only partially dissolved in salt of phosphorus. Strontium. — Like barium. Tin. — Like aluminum. Zinc. — Like antimony, but not made black by fusion with tin. 2. Oxides which Impart Decided Colors to the Beads. The colors in hot and cold beads of both fluxes and under both oxidation and reduction are shown in the following table. The abbreviations are : sat = saturated ; fl = flamed ; op = opaque. OPERATIONS OF BLOWPIPE ANALYSIS. 105 Hot and cold relate to same bead ; kot and cold to larger amounts of the oxide. Oxides of Violet. Blue Green. Red. Brown. Yellow. Col'l'ss Chromium, O.F. R.F. cold hot, cold hot hot Cobalt, O.F. R.F. hot, cold hot, cold Copper, Iron, O.F. R.F. cold hot cold {0^.) cold hot rfi O.F. R.F. hot, cold hot hot, cold cold H ■< W Manganese. O.F. R.F. hot cold \ cold hot, cold X! Molybdenum, O.F R.F. hot (sat.) hot, cold hot cold y Nickel, O.F. R.F. hot flamed cold hot, cold Titanium, O.F. R.F. hot, cold cold hot hot, cold hot, cold Tungsten, O.F. R.F. hot hot, (sat.) hot hot, cold cold Uranium, O.F. R.F. hot, cold hot hot, cold ^fl.) Vanadium, O.F R.F. cold hot, cold hot, cold Oxides of Violet. Blue. Green. cold cold Red. Brown. Yellow. Col'l'ss Chromium, O.F. R.F. hot hot Cobalt, O.F. R.F. hot, cold hot, cold ifi Q <: w m Copper, O.F. R.F. cold hot hot cold (op.) Iron, O.F. R.F. hot hot, cold cold cold hot, cold hot cold cold Manganese, O.F. R.F. hot, cold hot, cold CM Molybdenum, O.F. R.F. hot hot, cold cold Nickel, O.F. R.F. hot hot cold cold hot hot 5 Titanium, O.F. R.F. cold hot, cold Tungsten, O.F. R.F. O.F. R.F. cold hot hot (sat.) hot, cold Uranium, cold hot, cold hot hot, cold Vanadium, O.F. R.F. cold hot io6 BLOWPIPE ANALYSIS. Flaming. Some substances yield a clear glass with borax or salt of phos- phorus, which remains clear when cold, but at a certain point near saturation if heated slowly and gently or with an intermittent flame, or unequally, or by alternate oxidizing flame and reducing flame, the bead becomes opaque and enamel-like. The reason is an incomplete fusion by which a part of the base is separated in the crystalline form. Flaming is hindered or quite prevented by silica. The borax beads may in general be said to be colored more intensely by equal amounts of coloring oxides, than the salt of phosphorus beads while the latter may be said to yield the greater variety in color. Use of Tin with Beads. Reduction is sometimes assisted by transferring the borax or salt of phosphorus bead to charcoal and fusing it for a moment with a grain or two of metallic tin. The tin oxidizes and takes its oxygen partly from the oxides in the bead. Use of Lead and Gold with Beads. Minute amounts of reduced metals, such as Cu, Ni, Co, may be collected from a bead by fusing it on charcoal with a small button of lead or gold. The glass bead can then be examined for the non- reducible oxides, and the lead or gold can by oxidation in contact with borax or salt of phosphorus, be made again to yield oxide colors from the reduced metals. Separate the button and the slag, saving both, and heat the button with boracic acid to remove the lead, and then with frequently changed S. Ph. The metals which have united with the gold or lead will be successively oxidized, and their oxides will color the S. Ph. in the following order : Co. — Blue, hot ; blue, cold. May stay in the slag. Ni. — Brown, hot ; yellow, cold. May give green with Co or Cu. Cu. — Green, hot ; blue, cold. Made opaque red by tin and re- ducing flame. The slag should contain the more easily oxidizable metals, and be free from Cu, Ni and Ag. Reduction Color Tests. Saturate two S. Ph. beads with the substance in the oxidizing flame, treat one of them on charcoal with tin and strong reduc- ing flame, pulverize and dissolve separately in cold dilute (1-4) OPERATIONS OF BLOWPIPE ANALYSIS. 107 hydrochloric acid with the addition of a little tin. Let the solu- tions stand for some time and then heat them to boiling. The Oxidized Bea d Yields In Cold Solution, In Hot Solution, w M( Ti. V. Cr. Ur, The Reduced Bead Yields In Cold Solution. In Hot Solution. Mo. Ti Blue. Deep Blue. Deep Blue. Deep Blue. ^, Wine Brown. Blue. Brown. Faint Brownwith Black Precipitate. ■c- • 4. Tr- 1 i Violet and Famt Violet. 1 urbid. Violet and Turbid. Violet. Bluish Green. Green. Green. Green. Green. Green. Green. Green. Green. Green. Green. Green. Tests with Sodium Thiosulphate. Na.S.Oj. A powdered metallic compound mixed with the dry flux, and either heated in a closed tube or upon a borax bead inside the blue flame will show the same color as would be produced by passing HjS through a solution of the compound. White = Zn. Orange ^ Sb. Yellow = Cd, As. Brown = Sn, Mo. Green = Cr, Mn. Black = Pb, Fe, Co, Cu, Ni, Ur, Bi, Ag, Au, Pt, Hg. Use of Acids. Acids are chiefly used in blowpipe work to expel and detect volatile constituents, to determine ease of solubility or to assist flame tests. Volatile constituents are released with bubbling (effervescence), and the constituent is detected by the odor, or sometimes by passing the gas into another reagent. Generally a colorless odor- less gas shows the mineral to be a carbonate. The mineral substance to be treated should be ground to fine powder, unless otherwise stated. Hydrochloric acid is commonly used but nitric acid is often needed for metallic minerals. Solubility may be : With effervescence in the cold. With effervescence only on heating. Quiet and easy. Difficult and incomplete. With separation of perfect jelly. io8 BLOWPIPE ANALYSIS. With separation of imperfect jelly. With separation of powder. With separation of crystals. Tests with Cobalt Solution, Cobalt nitrate dissolved in ten parts of water is used to moisten light colored infusible substances. These are then heated to redness in the oxidizing flame and colored compounds result. Blue, Al^O, and minerals containing it. Silicates of zinc. Green (bluish) Sn02. Green (yellowish), ZnO, TiO^. Green (dark), oxides of antimony and columbium. Flesh Color, MgO, and minerals containing it. Test with Magnesium Ribbon. Build a little pyramid of the powdered substance on char- coal, around a half inch length of magnesium ribbon and ignite the ribbon by touching with the flame ; after the flash place in water. Odor of PH, = P. Tests with Acid Potassium Sulphate. This reagent may be used to decompose insoluble compounds preparatory to wet separation, but its use in blowpipe analysis is chiefly to release volatile vapors and as a component of bismuth flux and boracic acid flux. Color of Fumes. Odor. ' Remarjcs. Indicating. Brown. Pungent. From nitrates. NO,. Brown. Choking. Turn starch paper yellow. Br. Violet. Choking. Turn starch paper violet. I. Yellowish- ■green. Chlorine. Explosive. CIO,. Colorless. Colorless. Burning sulphur. Pungent. SO,. HF. Corrodes the glass. Colorless. Chlorine. White vapors with NH,. HCl. Colorless. Bad eggs. Blacken lead acetate paper. H^S. Colorless. Almonds. Whitens lime water. HCN. Colorless. Odorless. Whitens lime water. CO^. OPERATIONS OF BLOWPIPE ANALYSIS. 109 Others of minor importance, acetic acid, chromic acid, organic acids, etc. Tests with Potassium Chlorate. Heat gradually in a matrass with the chlorate ; finally there will be an energetic oxidation, and the fused mass will be : Black = Ni, Cu. Bluish black = Co. Purple = Mn. Brown = Pb. Flesh color = Fe. Tests with Boracic Acid Flux. Grind 4^ parts KHSO^, i part CaFj to paste with water, add substance, thoroughly mixing. Heat at tip of the blue flame. Just after the water is driven off there may be yellow green flame of boron, or carmine flame of lithia. Use of Boracic Acid. Is used to' separate lead and bismuth from antimony, copper, cadmium, silver, etc. CHAPTER XIII. SUMMARY OF USEFUL TESTS WITH THE BLOWPIPE. The details of ordinary manipulations, such as obtaining beads, flames, coatings and sublimates, are omitted and the results alone stated; unusual manipulations are described. The bead tests are supposed to be obtained with oxides ; the other tests are true, in general, of all compounds not expressly excluded. The course to be followed in the case of interfering elements is briefly stated. ALUMINUM, Al. With Soda. — Swells and forms an infusible compound. With Borax or S. Ph. — Clear or cloudy, never opaque. With Cobalt Solution.* — Fine blue when cold. AMMONIUM, NH,. In Closed Tube. — Evolution of gas with the characteristic odor. Soda or lime assists the reaction. The gas turns red litmus paper blue and forms white clouds with HCl vapor. ANTIMONY, Sb. On Coal, R. F.\ — Volatile white coat, bluish in thin layers, con- tinues to form after cessation of blast and appears to come directly off the mass. With Bismuth Flux : On Plaster. — Peach-red coat, somewhat mottled. On Coal. — Faint yellow or red coat. * Certain phosphates, borates and fusible silicates become blue in absence of alumina. ■j- This coat may be further tested by S , Ph. or flame. USEFUL TESTS WITH THE BLOWPIPE. in In Open Tube. — Dense, white, non-volatile, amorphous sublimate. The sulphide, too rapidly heated, will yield spots of red. In Closed Tube. — The oxide will yield a white fusible sublimate of needle crystals, the sulphide, a black sublimate red when cold. Flame. — Pale yellow-green. With S. Ph. — Dissolved by O. F. and fused on coal with tin in R. F. becomes gray to black. Interfering Elements. Arsenic. — Remove by gentle O. F. on coal. Arsenic with Sulphur. — Remove by gentle heating in closed tube. Copper. — The S. Ph. bead with, tin in R. F. may be momentarily red but will blacken. Lead or Bismuth. — Retard formation of their coats by inter- mittent blast, or by adding boracic acid. Confirm coat by flame, not by S. Ph. ARSENIC, As. On Smoked Plaster. — White coat of octahedral crystals. On Coal. — Very volatile white coat and strong garlic odor. The oxide and sulphide should be mixed with soda. With Bismuth Flux: On Plaster. — Reddish orange coat. Oji Coal. — Faint yellow coat. In Open lube. — White sublimate of octahedral cr)'stals. Too high heat may form deposit of red or yellow sulphide. In Closed Tube. — May obtain white oxide, yellow or red sul- phide, or black mirror of metal. If the tube is broken and the mirror heated, a strong garlic odor will be noticed. Flame. — Pale azure blue. Interfering Elements. Antimony. — Heat in closed tube with soda and charcoal, break and treat resulting mirror in O. F. for odor. Cobalt or Nickel. — ¥\ist in O. F. with lead and recognize by odor. Sulphur. — {a) Red to yellow sublimate of sulphide of arsenic in closed tube. (b) Odor when fused with soda on charcoal. 112 BLOWPIPE ANALYSIS. BARIUM, Ba. On Coal with Soda. — Fuses and sinks into the coal. Flame. — Yellowish green improved by moistening with HCl. With Borax or S. Ph. — Clear and colorless, can be flamed opaque-white. BISMUTH, Bi. On Coal. — In either flame is reduced to brittle metal and yields a volatile coat, dark orange yellow hot, lemon yellow cold, with yellowish-white border. With Bismuth Flux .■* On Plaster. — Bright scarlet coat surrounded by chocolate brown, with sometimes a reddish border. The brown may be made red by ammonia.f On Coal. — Bright red coat with sometimes an inner fringe of yellow. With S. Ph. — Dissolved by O. F. and treated on coal with tin in R. F. is colorless hot but blackish gray and opaque cold. Interfering Elements. Antimony. — Treat on coal with boracic acid, and treat the re- sulting slag on plaster with bismuth flux. Lead. — Dissolve coat in S. Ph. as above. BORON, B. All borates intumesce and fuse to a bead. Flame. — Yellowish green. May be assisted by : [a) Moistening with HjSO^; (/;) Mixing to paste with water, and boracic acid flux (4^ pts. KHSO^, I pt. CaFj) ; {c) By mixing to paste with H,SO, and NH,F. BROMINE, Br. With S. Ph. Saturated With CuQ. — Treated at tip of blue flame, the bead will be surrounded by green and blue flames. In Matrass With KHSO^. — Brown choking vapor. Interfering Elements. Silver. — The bromide melts in KHSO4 and forms a blood-red globule which cools yellow and becomes green in the sunlight. * Sulphur 2 parts, potassic iodide I part, potassic bisulphate I part, t May be obtained by heating S. Ph. on the assay. USEFUL TESTS WITH THE BLOWPIPE. 113 CADMIUM, Cd. On CoalR. F. — Dark brown coat, greenish yellow in thin layers. Beyond the coat, at first part of operation, the coal shows a varie- gated tarnish. On Smoked Plaster with Bis^nuth Flux. — White coat made orange by (NHJ,S. With Borax or S. Ph. — O. F. clear yellow hot, colorless cold, can be flamed milk-white. The hot be^d touched to NajSjOj becomes yellow. R. F. Becomes slowly colorless. Interfering Elements. Lead, Bismuth, Zinc. — Collect the coat, mix with charcoal dust and heat gently in a closed tube. Cadmium will yield either a reddish brown ring or a metallic mirror. Before collecting coat treat it with O. F. to remove arsenic. CALCIUM, Ca. On Coal with Soda. — Insoluble and not absorbed by the coal. Flame. — Yellowish red improved by moistening with HCl. With Borax or S. Ph. — Clear and colorless, can be flamed opaque. CARBON DIOXIDE, CO,. With Nitric Acid. — Heat with water and then with dilute acid. COj will be set free with effervescence. The escaping gas will render lime-water turbid. With Borax or S. Ph. — After the flux has been fused to a clear bead, the addition of a carbonate will cause effervescence during further fusion. CHLORINE, CL With S. Ph. Saturated with CuO. — Treated at tip of blue flame, the bead will be surrounded by an intense azure-blue flame. On Coal with CuO. — Grind with a drop of HjSO^, spread the paste on coal, dry gently in O. F. and treat with blue flame, which will be colored greenish-blue and then azure-blue. CHROMIUM, Cr. With Borax or S. Ph. — O. F. Reddish hot, fine yellow-green cold. 114 BLOWPIPE ANALYSIS. R. F. In borax, green hot and cold. In S. Ph. red hot, green cold. With Soda. — O. F. Dark yellow hot, opaque and light yellow cold. ' R. F. Opaque and yellowish-green cold. Interfering Elements. Manganese.— The soda bead in O. F. will be bright yellowish- green. COBALT, Co. On Coal, R. F. — The oxide becomes magnetic metal. The solu- tion in HCl will be rose- red but on evaporation will be blue. With Borax or S. Ph. — Pure blue in either flame. Interfering Elements. Arsenic. — Roast and scorify with successive additions of borax. There may be, in order given : Yellow (iron), green (iron and cobalt), blue (cobalt), reddish-brown (nickel), green (nickel and copper), blue (copper). Copper and other Elements which Color Strongly. — Fuse with borax and lead on coal in R. F. The borax on platinum wire in O. F. will show the cobalt, except when obscured by much iron or chromium. Iron, Nickel or Chromium. — Fuse in R. F. with a little metallic arsenic, then treat as an arsenide. Sulphur or Selenium. — Roast and scorify with borax, as before described. COPPER, Cu. On Coal R. F. — Formation of red malleable metal. Flamed — Emerald-green or azure-blue, according to compound. The azure-blue flame may be obtained : («) By moistening with HCl or aqua regia, drying gently in O. F. and heating strongly in R. F. [b) By saturating S. Ph. bead with substance, adding common salt, and treating with blue flame. With Borax \ or S. Ph. — O. F. Green hot, blue or greenish- blue cold. * Sulphur, selenium and arsenic should be removed by roasting. Lead necessitates a gentle heat. ■[■ By repeated slow oxidation and reduction, a borax bead becomes ruby red. USEFUL TESTS WITH THE BLOWPIPE. 115 R. F. Greenish or colorless hot, opaque and brownish-red cold. With tin on coal this reaction is more delicate. Interfering Elements. . General Method.* — Roast thoroughly, treat with borax on coal in strong R. F., and If Button Forms. — Separate the button from the slag, remove any lead from it by O. F., and makp either S. Ph. or flame test upon residual button. If no Visible Biitton Forms.— Add test lead to the borax fusion, continue the reduction, separate the button and treat as in next test. (Lead Alloy.) Lead or Bismuth Alloys. — Treat with frequently changed boracic acid in strong R. F., noting the appearance of slag and residual button. Trace. — A red spot in the slag. Over One Per Cent. — The residual button will be bluish-green when melted, will dissolve in the slag and color it red upon application of the O. F., or may be removed from the slag and be submitted to either the S. Ph. or the flame test. FLUORINE, F. Etching Test. — If fluorine is released it will corrode glass in cloudy patches, and in presence of silica there will be a deposit on the glass. According to the refractoriness of the compound the fluorine may be released : (a) In closed tube by heat. {Ji) In closed tube by heat and KHSO4 (c) In open tube by heat and glass of S. Ph. With Cone. H^SO^ and SiO.^- — If heated and the fumes condensed by a drop of water upon a platinum wire, a film of silicic acid will form upon the water. IODINE, I. With S. Ph. Saturated with C21O. — Treated at the tip of the blue flame the bead is surrounded by an intense emerald-green flame. ht Matrass with KHSO^. — Violet choking vapor and brown sublimate. * Oxides, sulphides, sulphates are best reduced by a mixture of soda and borax. ii6 BLOWPIPE ANALYSIS. In Open Tube with Equal Parts Bismuth Oxide, Sulphur and Soda. — A brick-red sublimate. With Starch Paper. — The vapor turns the paper dark purple. Interfering Elements. Silver. — The iodide melts in KHSO^ to a dark red globule, yel- low on cooling, and unchanged by sunlight. IRON, Fe. On Coal. — R. F. Many compounds become magnetic. Soda assists the reaction. With Borax.* — O. F. Yellow to red hot, colorless to yellow cold. R. F. Bottle-green. With tin on cbal, vitriol-green. With S. Ph. — O. F. Yellow to red hot, greenish while cooling, colorless to yellow cold. R. F. Red hot and cold, greenish while cooling. State of the Iron. — A borax bead blue from CuO is made red by FeO, and greenish by FejOj. Interfering Elements. Chromium. — Fuse with nitrate and carbonate of soda on pla- tinum, dissolve in water and test residue for iron. Cobalt. — By dilution the blue of cobalt in borax may often be lost before the yellow of iron. Copper. — May be removed from borax bead by fusion with lead on coal in R. F. Manganese. — [a) May be faded from borax bead by treatment with tin on coal in R. F. ib) May be faded from S. Ph. bead by R. F. Nickel. — May be faded from borax bead by R. F. Tungsten or Titanimn.—The. S. Ph. bead in R. F. will be reddish- brown instead of blue or violet. Uranium.- — As with chromium. Alloys, Stdphides, Arsenides, etc. — Roast, treat with borax on coal in R. F., then treat borax in R. F. to remove reducible metals. LEAD, Pb. On Coal.\ — In either flame is reduced to malleable metal and - A slight yellow color can only be attributed to iron, when there is no decided color produced by either flame in highly charged beads of borax and S. Ph. f The phosphate yields no coat without the aid of a flux. USEFUL TESTS WITH THE BLOWPIPE. 117 yields, near the assay, a dark lemon-yellow coat, sulphur-yellow cold and bluish-white at border. With Bismuth Flux : On Plaster. — Chrome-yellow coat, blackened by (NH4),S. On Coal. — Volatile yellow coat, darker hot. Flame. — Azure-blue. With Borax or S. Ph.—Q. F. Yellow hot, colorless cold, flames opaque-yellow. R. F. Borax bead becomes clear, S. Ph. bead cloudy. Interfering Elements. Antimony. — Treat on coal with boracic acid, and treat the re- sulting slag on plaster with bismuth flux. Arsenic Sulphide. — Remove by gentle O. F. Cadmium. — Remove by R. F. Bismuth. — Usually the bismuth flux tests on plaster are sufficient. In addition the lead coat should color the R. F. blue. LITHIUM, Li. Flame, — Crimson, best obtained by gently heating near the wick. Interfering Elements. Sodium, {a) Use a gentle flame and heat near the wick, {b) Fuse on platinum wire with barium chloride in O. F. The flame will be first strong yellow, then green, and lastly, crimson. Calcium or Strontium. — As these elements do not color the flame in the presence of barium chloride, the above test will answer. Silicon. — Make into a paste with boracic acid flux and water, and fuse in the blue flame. Just after the flux fuses the red flame will appear. MAGNESIUM, Mg. On Coal with Soda. — Insoluble, and not absorbed by the coal. With Borax or S. Ph. — Clear and colorless can be flamed opaque- white. With Cobalt Solution.* — Strongly heated becomes a pale flesh color. MANGANESE, Mn. With Borax or S. Ph.\ — O. F. Amethystine hot, reddens on cool- * With silicates this reaction is of use only in the absence of coloring oxides. The phosphate, arsenate and borate become violet-red. + The colors are more intense with borax than with S. Ph. ii8 BLOWPIPE ANALYSIS. ing. With much, is black and opaque. If a hot bead is touched to a crystal of sodium nitrate an amethystine or rose-colored froth is formed. R. F. Colorless or with black spots. With Soda. — O. F. Bluish-green and opaque when cold. Sodium nitrate assists the reaction. Interfering Elements. Chromium. — The soda bead in O. F. will be bright yellowish- green instead of bluish-green. Silicon. — Dissolve in borax, then make soda fusion. MERCURY, Hg. With Bismuth Flux : On Plaster. — Volatile yellow and scarlet coat. If too strongly heated the coat is black and yellow. On Coal. — Faint yellow coat at a distance. In Matrass with Dry Soda or with Litharge^ — Mirror-like sublimate, which may be collected in globules. MOLYBDENUM, Mo. On Coal. — O. F. A coat yellowish hot, white cold, crystalline near assay. R. F. The coat is turned in part deep blue, in part dark copper-red. Flame. — Yellowish-green. With Borax. — O. F. Yellow hot, colorless cold. R. F. Brown to black and opaque. With S. Ph. — O. F. Yellowish-green hot, colorless cold.f R. F. Emerald-green. Dilute (^) HCl Solutions. — If insoluble the substance may first be fused with S. Ph. in O. F. If then dissolved in the acid and heated with metallic tin, zinc or copper, the solutions will be suc- cessively blue, green and brown. If the S. Ph. bead has been treated in R. F. the solution will become brown. * Gold-leaf is whitened by the slightest trace of vapor of mercury. f Crushed between damp unglazed paper becomes red, brown, purple or blue, ac- cording to amount present. USEFUL TESTS WITH THE BLOWPIPE. 119 NICKEL, Ni. On Coal. — R. F. The oxide becomes magnetic. With Borax.— O. F. Violet hot, pale reddish-brown cold. R. F. Cloudy and finally clear and colorless. With S. Ph.—O. F. Red hot, yellow cold. R. F. Red hot, yellow cold. On coal with tin becomes colorless. Interfering Elements. General Method. — Saturate two orthree borax beads with roasted substance, and treat on coal with a strong R. F. If a visible button results, separate it from the borax, aud treat with S. Ph. in the O. F., replacing the S. Ph. when a color is obtained. If no visible button results, add either a small gold button or a few grains of test lead. Continue the reduction, and : With Gold. — Treat the gold alloy on coal with S. Ph. in strong O. F. With Lead. — Scorify button with boracic acid to small size, complete the removal of lead by O. F. on coal, and treat residual button with S. Ph. in O. F. Arsenic. — Roast thoroughly, treat with borax in R. F. as long as it shows color, treat residual button with S. Ph. in O. F. Alloys. — Roast and melt with frequently changed borax in R, F. adding a little lead if infusible. When the borax is no longer colored, treat residual button with S. Ph. in O. F. NITRIC ACID, HNO3. In Matrasswith KHSO^,orin Closed Tube with Litharge. — Brown fumes with characteristic odor. The fumes will turn ferrous sul- phate paper brown. PHOSPHORUS. P. Flame. — Greenish-blue, momentary. Improved by cone. HjSO^. hi Closed Tube with Dry Soda and Magnesium. — The soda and substance are mixed in equal parts and dried, and made to cover the magnesium. Upon strongly heating there will be a vivid in- candescence, and the resulting mass, crushed and moistened, will yield the odor of phosphuretted hydrogen. POTASSIUM, K. Flame. — Violet, except borates and phosphates. 1 ? D BLO WPIPE ANAL YSIS. Interfering Elements. Sodium. — {a) The flame, through blue glass, will be violet or blue. (3) A bead of borax and a little boracic acid, made brown by nickel, will become blue on addition of a potassium compound. Lithium. — The flame, through green glass, will be bluish-green. SELENIUM, Se. On Coal, R. F. — Disagreeable horse-radish odor, brown fumes, and a volatile steel-gray coat with a red border. In Open Tube. — Steel-gray sublimate, with red border, some- times white crystals. In Closed Tube. — Dark-red sublimate and horse-radish odor. Flame. — Azure-blue. On Coal with Soda. — Thoroughly fuse in R. F., place on bright silver, moisten, crush, and let stand. The silver will be blackened. SILICON, SI. On Coal rvith Soda. — With its own volume of soda, dissolves with effervescence to a clear bead. With more soda the bead is opaque. With Borax. — Clear and colorless. With S. Ph. — Insoluble. The test made upon a small fragment will usually show a translucent mass of undissolved matter of the shape of the original fragment. When not decomposed by S. Ph., dissolve in borax nearly to saturation, add S. Ph., and re-heat for a moment. The bead will become milky or opaque white. SILVER, Ag. On Coal. — Reduction to malleable white metal. With Borax or S. Ph. — O. F. Opalescent. Cupellation. — Fuse on coal with i vol. of borax glass and i to 2 vols, of test lead in R. F. for about two minutes. Remove button and scorify it in R. F. with fresh borax, then place button on cupel and blow O. F. across it, using as strong blast and as little flame as are consistent with keeping button melted. If the litharge is dark,orif the button freezes before brightening, or if it brightens but is not spherical, rescorify it on coal with borax. USEFUL TESTS WITH THE BLOWPIPE. 121 add more test lead, and again cupel until there remains only a white spherical button of silver. SODIUM, Na. Flame. — Strong reddish-yellow. STRONTIUM, Sr. On Coal with Soda. — Insoluble, absorbed by the coal. Flame. — Intense crimson, improved by moistening with HCl. With Borax or S. Ph. — Clear and colorless; can be flamed opaque. Interfering Elements. Barium. — The red flame may show upon first introduction of the sample into the flame, but it is afterward turned brownish- yellow. Lithium. — Fuse with barium chloride, by which the lithium flame is unchanged. SULPHUR, S. On Coal with Soda and a Little Borax. — Thoroughly fuse in the R. F., and either : («) Place on bright silver, moisten, crush and let stand. The silver will become brown to black. Or, ((5) Heat with dilute HCl (sometimes with powdered zinc) ; the odor of HjS will be observed. In Open Tube. — Suffocating fumes. Some sulphates are unaf- fected. In Closed Tube. — May have sublimate red when hot, yellow cold, or sublimate of undecomposed sulphide, or the substance may be unaffected. With Soda and Silica (equal parts). — A yellow or red bead. To Determine Whether Sulphide or Sulphate. — Fuse with soda on platinum foil. The sulphide only will stain silver. TELLURIUM, Te. On Coal. — Volatile white coat with red or yellow border. If the fumes are caught on porcelain, the resulting gray or brown film may be turned crimson when moistened with cone. HjSO^, and gently heated. 122 BLOWPIPE ANALYSIS. On Coal with 5o^«.— Thoroughly fuse in R. F. Place on bright silver, moisten, crush and let stand. The silver will be blackened. Flame. — Green. In Open Tube.— Gra.y sublimate fusible to clear drops. With H^SO^ (cone.).— Boiled a moment, there, results a purple violet solution, which loses its color on further heating or on dilu- tion. TIN, 8n. On Coal. — O. F. The oxide becomes yellow and luminous. R. F. A slight coat, assisted by addition of sulphur or soda. With Cobalt Solution.— VL6\s'i&n the coal, in front of the assay, with the solution, and blow a strong R. F. upon the assay. The coat will be bluish-green when cold. With CuO in Borax Bead. — A faint blue bead is made reddish- brown or ruby-red by heating a moment in R. F. with a tin com- pound. Interfering Elements. Lead or Bismuth {Alloys). — It is fair proof of tin if such an alloy oxidizes rapidly with sprouting and cannot be kept fused. Zinc. — On coal with soda, borax and charcoal in R. F. the tin will be reduced, the zinc volatilized ; the tin may then be washed from the fused mass. TITANIUM,=*=Ti. With Borax. — O. F. Colorless to yellow hot, colorless cold, opalescent or opaque-white by flaming. R. F. Yellow to brown, enamel blue by flaming. With S. Ph.—O. F. As with borax. R. F. Yellow hot, violet cold. HCl Solutions. — If insoluble the substance may first be fused with S. Ph. or with soda and reduced. If then dissolved in dilute acid and heated with metallic tin, the solution , will become violet after standing. Usually there will also be a turbid violet precipi- tate, which becomes white. Interfering Elements. Iroti. — The S. Ph. bead in R. F. is yellow hot, brownish-red cold. TUNGSTEN, W. With Borax. — O. F. Colorless to yellow hot, colorless cold, can be flamed opaque-white. * If the substance is mixed with sodium fluoride, fused on platinum witli a little sodium pyrosulphate and dissolved by boiling in a very weak solution of sulphuric acid, the addition of a few drops of hydrogen peroxide will produce a color like that of ferric chloride. USEFUL TESTS WITH THE BLOWPIPE. 123 R. F. Colorless to yellow hot, yellowish-brown cold. With S. Ph. — O. F. Clear and colorless. R. F. Greenish hot, blue cold. On long blowing or with tin on coal, becomes dark green. With Dilute HCl. — If insoluble, the substance may first be fused with S. Ph. The solution heated with tin becomes dark blue ; with zinc it becomes purple and then reddish-brown. Interfering Elements. Iron. — The S. Ph. in R. F. is yellow hot, blood-red cold. URANIUM, U, With Borax. — O. F. Yellow hot, colorless cold, can be flamed enamel yellow. R. F. Bottle-green, can be flamed black but not enamelled. With S. Ph. — O. F. Yellow hot, yellowish-green cold. R. F. emerald-green. Interfering Elements. Iron. — With S. Ph. in R. F. is green hot, red cold. VANADIUM, V. With Borax. — O. F. Colorless or yellow hot, greenish-yellow R. F. Brownish hot, emerald-green cold. With S. Ph. — O. F. Dark yellow hot, light yellow cold. R. F. Brown hot, emerald-green cold. H^SOi Solutions. — Reduced by Zn become successively yellow, green, bluish-green, blue, greenish-blue, bluish-violet and lavender. ZINC, Zn. On Coal. — O. F. The oxide becomes yellow and luminous. R. F. Yellow coat, white when cold, assisted by soda and a little borax. With Cobalt Solution. — Moisten the coal, in front of the assay, with the solution, and blow a strong R. F. upon the assay. The coat will be bright yellow-green when cold. 124 BLOWPIPE ANALYSIS. Interfering Elements. Antimony. — Remove by strong O. F., or by heating with'sulphur in closed tube. Cadmium, Lead or Bismuth. — The combined coats will not pre- vent the cobalt solution test. Tin. — The coats heated in an open tube, with charcoal dust by the O. F., may yield white sublimate of zinc. CHAPTER XIV. SCHEMES FOR QUALITATIVE BLOWPIPE ANALYSIS. Test I.* — Heat a portion gently with O. F. upon charcoal or a plaster tablet which has been blackened in the lamp flame. As. — White very volatile crystalline coat, white fumes having garlic odor and invisible near assay, best on plaster. The coat disappears before R. F. , tingeing it pale blue and evolving the characteristic garlic odor. Confirmation As. — The coating may be scraped off together with a little charcoal and if heated in closed tube should yield an arsenic mirror ; or it may be dissolved in solution of KOH, placed in a test tube, a small pjece of sodium amalgam added, and the tube covered with a piece of filter paper moistened with a slightly acid solution of AgNOj. The paper will be stained black by the AsHj evolved. Sb. — White fumes and white pulverulent volatile coat, best on charcoal. A good distinguishing feature between As and Sb is as follows : They both usually continue to give off fumes after removal of the flame, but while still hot the AsjOj fumes are not visible within one-half inch of assay, while SbjO^ fumes appear to come imme- diately from the mass. Confirmation Sb. — The coating disappears before R. F., tingeing it a pale yellow- green, or, if scraped together, dissolved in S. Ph. and jtcst fused on charcoal in contact with tin it will form a gray or black opaque bead. If the coating be scraped off and dissolved in tartaric acid -|- HCl, and the solution placed in a platinum capsule with a piece of zinc, Sb, if present, will give a black adherent stain. This may be confirmed by washing the stain with water, then dissolv- ing it in a few drops of hot tartaric acid plus a drop or two of HCl ; on adding HjS, an orange precipitate proves Sb^Sj. Most antimony minerals leave a white residue when treated with concentrated nitric acid. If this residue is washed with water dissolved in HCl and HjS added, an orange precipitate of SbjSj will be formed. *Test I. may also yield white coating of chlorides or lead sulphate, or of Se or Te, non-volatile coatings of Sn or Zn near the assay, yellow hot and white cold ; yellow coatings of Pb or Bi ; crystalline yellow and white coating of Mo ; and deep brown coating of Cd. All of these will be detected with greater certainty by later tests. 126 BLOWPIPE ANALYSIS. Test II. — Mix a portion with soda and a little borax and heat strongly upon charcoal with R. F. for three or four minutes. Preserve the fused mass for' subsequent examination. Or, mix some of the powdered substance with metallic sodium by means of a knife blade, ignite carefully on charcoal and heat residue with blowpipe flame to obtain coatings or to fuse to- gether any metallic particles* Preserve residue for Test III. As — Garlic odor, white fumes and a white volatik coat. Sb. — White fumes and a white volatile coat. Cd. — Dark brown volatile coat, sometimes shading to greenish- yellow and usually surrounded by a variegated coloration resem- bling the colors of peacock feathers. CONFIKMATION Cd. — The coat forms at first heating, and, if mixed with NajSjOj and fused in a borax bead, will form a bright yellow mass of CdS, Zn. — White not easily volatile coat, yellow when hot. Sn. — White non-volatile coat close to assay, yellow while hot and usually small in amount. Confirmation Zn and Sn. — If any coat forms, moisten it with cobalt solution and blow a strong blue flame on the substance. The coatings from otherjelements will not prevent the cobalt coloration. The zinc coat is made bright yellowish green. The tin coat becomes bluish-green. Test III. — Crush, and pulverize and examine the residue of Test II. I. Collect any magnetic particles with the magnet; dissolve some of the magnetic particles in a borax bead with the O. F. Try also effect of R. F. Fe — The bead is : O. F. hot, yellow to red ; O. F. cold, color- less to yellow ; R. F. cold, bottle-green. Confirmation Fe. — The magnetic particles yield with HNO3, a brown solution from which, after evaporating excess of acid, K^FeCy^ throws down a blue precipitate. Ni. — The bead is : O. F. hot, intense violet ; O. F. cold, pale brown ; R. F. cold, colorless. Confirmation Ni. — If the excess of acid is driven off by evaporation, KCy added in excess, and the solution then made strongly alkaline with KOH, two or three drops of pure bromine will give a black precipitate of Ni2(0H)j. Co. — The bead is : O. F. and R. F. hot or cold, a deep pure blue ; if greenish when hot, probably Fe or Ni is also present. Confirmation Co. — The magnetic particles yield with HNO3, a rose-red solution which becomes blue on evaporation. * Test II. may also yield white coats from Pb, Bi or alkalis, yellow coats from Pb or Bi, brown or red coats from Cu or Mo, and the ash of the coal may be white or red. SCHEMES FOR QUALITATIVE ANALYSIS. 127 2. Examine residue for metallic buttons and observe if they are malleable or not. Ag. — Silver white malleable button. Confirmation Ag. — Dissolve button in dilute HNO3, and add a drop of HCl. A white precipitate, soluble in NH^OH is obtained. Pb — Lead gray malleable button. Confirmation Pb. — With bismuth flux on charcoal gives yellow coating. Sn. — White malleable button. Confirmation Sn. — Heated in O. F. on charcoal gives a non-volatile coating, yellow hot and white cold. Decomposed in cone. HNO3 with white residue of metastannic acid. Cu. — Reddish malleable button. Confirmation Cu. — Dissolves in HNO3 to a green solution rendered intense blue when neutralized with NHjOH. Au. — Yellow malleable button. Confirmation Au. — Insoluble in HNO3 or HCl alone, but dissolved by mixed acids. Bi. — Reddish white brittle button. Confirmation Bi. — Heat with bismuth flux. Sb. — White brittle button, yielding white coating before the blowpipe. 3. Dig up some of the charcoal beneath assay, place upon a bright silver surface ; moisten with water and let stand. S, Se, Te.— The bright silver is stained black or dark-brown, and unless the horseradish odor of Se or the brown coatings of Se and Te with bismuth flux have been already obtained, this stain will prove sulphur. Confirmations S.— The soda fusion will evolve HjS when moistened with HCl. By holding in the gas a piece of filter paper moistened with a drop or two of lead acetate (test is made more sensitive by adding a drop of ammonia to the acetate), the paper will be stained black. Confirmation Se.— Characteristic disagreeable horseradish odor during fusion. Confirmations Te.— If a little of the original substance is dropped into boiUng concentrated H2SO4, a deep violet color is produced; this disappears on further heating. The quite cold soda fusion added to hot water produces a purple-red solution. Test IV.— Mix a portion of the substance with more than an equal volume of bismuth flux,* and heat gently upon a plaster tablet with the oxidizing flame. * Formed by grinding together I part KI, part KHSO^, 2 parts S. ,28 BLOWPIPE ANALYSIS. Pb.— Chrome-yellow coat, darker hot, often covering the entire tablet. Confirmation Pb. — If the test is made oa charcoal, the coat is greenish-yellow, brown near the assay. Hg. — Gently heated, bright scarlet coat, very volatile, and with yellow fringe; but if quickly heated, the coat formed is pale-yel- low and black. Confirmation Hg. — If the substance is heated gently in a closed tube or matrass with dry soda or Ktharge, a mirror-like sublimate will form, which may be collected into little globules of Hg by rubbing with a match end. The test with bismuth flux on charcoal yields only a faint yellow coat. Bi. — Bright chocolate-brown coat, with sometimes a reddish fringe. Confirmations Bi.— The coat is turned ora,nge-yellow, then cherry-red, by fumes of NH3, which may conveniently be produced by heating a few crystals of S. Ph. on the assay. The test with bismuth flux on charcoal yields a bright-red band, with sometimes an inner fringe of yellow. Sb. — Orange to peach-red coat, very dark when hot. Confirmation Sb. — The coat becomes orange when moistened with (NH4)2S. Test IV. may yield colored sublimates with large amounts of certain other elements, and on smoked plaster certain white sublimates are obtainable. In all cases the elements are detected with greater certainty by other tests, but for convenience they are here summarized : Sn, brownish-orange ; As, reddish-orange ; Se, reddish-brown ; Te, purplish-brown, with deep brown border; Mo, deep ultramarine blue; Cu, Cd, Zn, white on smoked plaster. Test V. — Dissolve substance in salt of phosphorus in O. F. so long as bead remains clear on cooling. Treat then for three or four minutes in a strong R. F. to remove volatile compounds. Note the colors hot and cold, then re-oxidize and note colors hot and cold. Fe, Ti, Mo, W. — The bead in O. F. cold is colorless or very FAINT YELLOW. Confirmation Fe. — The bead in its previous treatment should have been O. F. hot, yellow to red ; O. F. cold, colorless ; R. F. cold, bottle green. Confirmation Ti. — The bead is reduced on charcoal with tin, pulverized and dis- solved in J HCl with a little metallic tin. The reduced bead is violet, the solution is violet and turbid. Confirmations Mo. — Tested as above on charcoal with tin, etc., the reduced bead is green, the solution is dark brown. Heat a little of the substance on platinum foil with a few drops of cone. HNO3, heat until excess of HNO3 ^^^ ^'1 volatilized, then add SCHEMES FOR QUALITATIVE ANALYSIS. 129 few drops of strong H^SO^ and heat until copious fumes are evolved ; cool, and breathe upon the cooled mass ; an ultramarine blue = Mo. Confirmation W. — Tested on charcoal with tin, etc., as above, the reduced bead is green, the solution is deep blue. Ur, V, Ni.* — The bead in O. F. cold, is colored yellow or GREENISH-YELLOW. Confirmation U.— The bead in R. F. is dull green, hot; iine green, cold. Make a Na^COj fusion, dissolve in HCl or H^SO^, add a few drops or H^S water, and if it gives any precipitate, add it in excess and filter ; to filtrate add a few drops of HNO3 and boil, then add NH^OH to alkaline reaction, filter, wash precipitate with ammonia water, and then treat precipitate with a concentrated solution of (NH^I^COj-l- NH,OH, filter, acidify filtrate with HC], and add KjFeCyg. Brown ppt. = Ur. Confirmation V. — In R. F. the bead will be brownish hot, fine green cold. Fuse substance with NajCOj in O. F., and dissolve fusion in a few drops of dilute HjSOj or HCl, add a piece of zinc and warm ; blue color changing to green and finally vio- let = V. Confirmation Ni. — A borax bead in O. F. will be intense violet, and in R. F. will be reddish hot, yellow cold. Mn. — The bead in O. F., cold, is colored violet ; if touched while hot to a crystal of nitre, it is made deep permanganate color. Confirmation Mn. — Fused on platinum wire in O. F., with a paste of soda, and nitre, manganese yields an opaque bluish-green bead. Cr. — The bead in O. F., cold, is colored green. * If the absence of Ni is not proved, or Co obscures the tests, dissolve the substance in borax on charcoal to saturation, and treat for five minutes in hot R. F. If a visible button results, separate it from the borax, and treat with S. Ph. in the O. F., replacing the S. Ph. when a color is obtained. If no visible button results, add either a small gold button or a few grains of test lead. Continue the reduction, and, if lead has been used, scorify the button with fre- quently changed boracic acid to small size, stopping the instant the boracic acid is colored by Co, Ni, or Cu, blue, yellow, or red, respectively. Complete the removal of lead by O. F. on coal, and treat as below. Treat the gold alloy, or the residual button from the lead alloy, on coal, with fre- quently changed S. Ph., in strong O. F. The metals which have united with the gold or lead, will be successively oxidized and their oxides will color the S. Ph. in the following order ; Co. — Blue, hot ; blue, cold. May stay in the slag. Ni. — Brown, hot; yellow, cold. May give green with Co or Cu. Cu. — Green, hot; blue, cold. Made opaque red by tin and R. F. The slag should contain the more easily oxidizable metals, and be free from Cu, Ni, and Ag. Test a portion with S. Ph. and tin to prove absence of Cu. If present, it must be removed by further reduction with lead. Pulverize the slags and dissolve a portion in S. Ph., and examine by Test V. I30 BLOWPIPE ANALYSIS. I There may be a green bead from admixture of a blue and a yellow. If Cr is not proved, examine in such a case for Ur, V, Cr, etc., with unusual care. Confirmation Cr. — If the substance is fused on platinum wire in the O.F. with a paste of soda and nitre, an opaque yellow bead is produced ; and if the soda bead is dissolved in water, filtered, acidified with acetic acid, and a drop or two of lead acetate added, a yellow precipitate will be formed. Co, Cu. — The bead in O. F., cold, is colored blue. Confirmation Co. — The bead is deep blue, hot and cold, in both flames. Confirmation Cu. — The bead is green, hot, greenish-blue, cold, and on fusion with tin on coal becomes opaque brownish-red. With larger percentage of copper, the substance will yield a mixed azure-blue and green flame on heating with HCl. SiOj, AI2O3, TiO^, SnOj — The saturated bead contains an ap- preciable amount of insoluble material, in the form of a trans- lucent cloud, jelly-like mass, or skeleton form of the original material. Confirmation SiO^. — Mix the dry substance with a little dry calcium fluoride free from SiOj, place in a dry test tube and add cone. H^SO^ and heat gently, hold in fumes given off, a drop of water in loop of platinum wire ; SiOj will be separated on coming in contact with the water and form a jelly-like mass. Silica or silicates fused with soda unite with noticeable effervescence. Confirmation AI2O3, TiO„, SnOj, SiOj. — If infusible, moisten the pulverized mineral with dilute cobalt nitrate solution and heat strongly. AljOj. — Beautiful bright blue. TiOj. — Yellowish green. SnOj. — Bluish green. SiOj. — Faint blue ; deep blue, if fusible. There may also be blues from fusible phosphates and borates, greens from oxides of Zn, Sb, violet from Zr, various indefinite browns and grays, and a very character- istic pale pink or flesh color from Mg. Confirmation SnO^. — Treat the finely pulverized mineral with Zn and HCl in contact with platinum. Dissolve any reduced metal in HCl and test with HgCl2. There will be white or gray ppt. Ba, Ca, Sr, Mg. — The saturated bead is white and opaque and the nearly saturated bead can be flamed white and opaque. Confirmation Ba, Ca, Sr. — Moisten the flattened end of a clean platinum wire with dilute hydrochloric acid, dip it in the roasted substance, and heat strongly at the tip of the blue flame, and gently near the wick. Remoisten with the acid frequently. Ba. — Yellowish-green flame, bluish-green through green glass. Ca. — Yellowish-red (brick-red) flame, green through green glass. Sr. — Scarlet-red flame, faint yellpw through green glass. There may also be produced Li, carmine-red flame, invisible through green glass. SCHEMES FOR QUALITATIVE ANALYSIS. 131 K, rose-violet flame, reddish-violet througli blue glass. Na, orange-yellow flame, invisible through blue glass. Cu. azure-blue and emerald green. Se and As, pale blue. Mo, Sb, Te, pale green. Confirmation Mg. — Moisten the roasted substance with cobalt solution, and heat strongly. The substance will be colored pale pink or flesh color, or violet if present as either arsenate or phosphate. Test VI. — Cupellation for silver and gold. Fuse one vol. of the roasted substance on charcoal with i vol. of borax glass, and I to 2 vols, of test lead in R. F. for about two minutes. Remove button and scorify it in R F. with fresh borax, then place button on cupel and blow O. F. across it, using as strong blast and as little flame as are consistent with keeping the button melted. If the litharge is dark, or if the button freezes before brightening, or if it brightens but is not spherical, re- scorify it on charcoal with borax, add more test lead, and again cupel until there remains only a bright spherical button unaltered by further blowing. Ag. — The button is white. Au. — The button is yellow or white. Confirmation Ag and Au. — Dissolve in a drop of HNOj, and add a drop of HCl, producing a white curd-like precipitate. If gold is present there will be a resi- due insoluble in HNO3 which will become golden yellow on ignition. Test VII. — Heat substance in matrass with acid potassium sulphate. N2O5, Br. — Reddish brown vapor. Confirmation N^Oj. — The gas turns ferrous sulphate paper brown. Nitrates defla- grate violently when fused on charcoal. CI. — Colorless or yellowish green vapor, with odor of chlorine. I. — Violet choking vapor. Confirmation Br, CI, I. — Saturate a salt of phosphorus bead with CuO, add sub- stance, and treat in O. F. Br, azure blue and emerald green flame. Cl, azure blue flame with a little green. I, emerald green flame. Fuse with NajCOj, pulverize and mix with MuOj, and add a few drops of cone. HjSOj, and heat. Cl, yellowish green gas that bleaches vegetable colors. Br, red fumes. Fuse with Na^COg, dissolve in water, make slightly acid with HjSOj, and add Fe2(S04)3 (ferric alum may be used), and boil; I, violet fumes (turn starch paper blueV 132 BLOWPIPE ANALYSIS. F. — The glass of the matrass is corroded, and if SiOj is present a film of SiOj is often deposited on the glass. Confirmation F. — If the substance be mixed with silica and then heated with concentrated sulphuric acid, and the fumes caught on a drop of water held in a loop of platinum wire, gelatinous silica will form in the water. Test VIII. — Heat the substance gently with water to re- move air bubbles and then with dilute hydrochloric acid. CO.^. — Effervescence continuing after heat is removed. HjS, CI and H are sometimes evolved, but usually the odor will distinguish these. Confirmation COj. — If the gas is passed into lime water, a white cloud and ppt. will be produced. Test IX. — Place a piece of Mg wire in a closed tube, and cover the wire with a mixture of soda and the substance. Heat till the mass takes fire, cool and add water. P. — Evolution of phosphine, recognized by odor. Confirmation P. — Fuse a little of the substance, previously roasted if it contains As, with two or three parts.NajCOj and one of NaN03 dissolve in HNO3, and add excess of (NHj)jMoOj; yellow ppt. = PzOs- I" presence of SiOj it is well to confirm this ppt by dissolving it in dilute NHjOH, allowing it to stand for half an hour and filtering off any SiOj that separates, then to filtrate adding magnesia mixture (MgClj -f- NHjCl + NH^OH) ; white ppt. = Yf>^. Phosphates yield a pale momentary bluish green flame when moistened with con- centrated HjSOj and treated at the tip of the blue flame. Test X. — Make a paste of four parts KHSO„ one part CaF,, water and substance. Treat at tip of blue flame. Just after water is driven off the flame will be colored. B. — Bright green. Li. — Carmine. Confirmation B. — Heat some of the substance gently on platinum wire, then add a drop of concentrated H^SO^, heat very gently again, just enough to drive off excess of HjSOj, dip in glycerine, hold in flame until glycerine begins to burn, remove from flame, and the mass will continue burning with a green flame. Turmeric paper, moist- ened with an HCl solution containing boron and dried at 100°, is turned a reddish brown which ammonia blackens. Test XI — Make a paste of the powdered substance with strong HCl. Treat on platinum wire in the non-luminous flame of a Bunsen burner. Confirm results by the spectro- scope as directed on page 93. SCHEMES FOR QUALITATIVE ANALYSIS. 133 The color imparted to the flame is : Na, K, Alone. Yellow. Violet. Through blue glass. Invisible or pale blue, Reddish violet. Na and K. Yellow. Reddish violet. Ba, Mo, B, Ca, Sr, Yellowish green. Red. Scarlet. Bluish green. Greenish grey. Violet. Cu, f Azure blue, I / \ Emerald green, j \ Azure blue, Emerald green. Test XII. — Heat the substance in a closed tube.* HjO. — Moisture on the side of tube. Hg. — Metallic mirror collecting in globules. As. — Metallic mirror but no globules, Test XIII. t — Treat the finely powdered substance in a test tube with strong HCl. Observe the result, then boil. Effervescence. — If the substance is non-metallic the gas given off will almost always be COj showing that the substance was a carbonate. H^S is easily recognized by its odor. CI which is yellowish and very offensive would be given off only in a few cases by the action of some oxides on HCl. Confirm CO^. — A drop of lime water on the end of a glass rod held in the gas after it has been passed through water to free it from HCl will be rendered turbid. Confirm HjS. — A piece of filter paper moistened with lead ace- tate will be blackened if held in the gas. Confirm CI. — A piece of moistened red litmus paper held in the gas will be bleached. Gelatinous Residue. — If a gelatinous residue forms after boil- ing away the larger part of the acid a silicate was present. * Other sublimates may result as noted on page 102. f Substitute for test VIII when convenient. 134 BLOWPIPE ANALYSIS. SPECIAL SCHEME FOR DETECTION OF THOSE METALS WHICH WHEN PRESENT AS SILI- CATES USUALLY FAIL TO YIELD SATISFACTORY TESTS BEFORE THE BLOWPIPE. Remove the volatile constituents as thoroughly as possible by roasting, then heat gently in a platinum capsule, with HF and a few drops of concentrated H^SO^ as long as fumes are given off; add a little more HF and HjSO^, and heat again in the same way. When fusion is quite cold, dissolve in cbld water and filter. Filtrate a. — Divide into four parts and test as follows : 1. Add a piece of Zn or Sn and a little HCl, and heat. Ti. — A violet or blue solution. Confirmations Ti. — Nearly neutralize solution, and then add Na^SjOj, and boil. White ppt. = Ti. Or, make solution slightly alkaline, and then acidify slightly with HCl, and add Na^HPO^. White ppt. = Ti. 2. Add excess of KOH or NaOH, boil and filter, and to filtrate add excess of NH^Cl. and boil. Al. — White precipitate. Dissolve ppt., produced by the KOH or NaOH, in HCl, and add K^FeCyg. Fe. — Blue precipitate. 3. Add HCl ; then make alkaline with NH^OH and add (NH^S + (NHJ2C03 in slight excess, filter; to filtrate add Na^HPO^. Mg. — White crystalline precipitate. Confirmation Mg. — If phosphates are present, this test would not be reliable for Mg. In such cases test a few drops of the solution with HjS; if it causes any precipi- tate, saturate the whole of the solution with it, filter, and to filtrate add a few drops of HNO3, and boil to oxidize FeO, nearly neutralize with solution of Na2C03. If iron is not present, add >■ few drops of FejClg, enough to give a red precipitate with the sodium acetate, then dilute and add excess of sodium acetate, and boil, filter, and to filtrate add NH^OH + (NHJ^S, filter, to filtrate add Na^HPOi. White crystalline precipitate = Mg, 4. Add BaClj as long as it gives a precipitate, then Ba(0H)2 to alkaline reaction, boil, filter, and to filtrate add (NHJ^COj and NH^OH and heat, filter; evaporate filtrate to dryness and ignite to drive out NH^ salts. Test residue in flame for K and Na; dis- solve residue in a few drops of water, filter if necessary, and then add solution of PtCI^ and alcohol. SCHEMES FOR QUALITATIVE ANALYSIS. 135 K. — Yellow crystalline precipitate. Confirmation Na, K. — Mix i part of the silicate with 5-6 parts of precipitated CaCOj and i part of NH4CI, heat to redness in platinum capsule for thirty minutes being careful to apply heat gently at first, digest sintered mass in hot water, and filter | to filtrate add (NHJ^COj and NHjOH, heat and filter, evaporate filtrate to dryness and ignite gently until all ammonium salts are driven off, then determine Na and K as above. Residue a — Boil with strong solution of (NHJ^SO^ and filter. Filtrate b. — Add a few drops of H^S water ; if any precipitate forms, saturate with HjS and filter, and to filtrate add NH4OH and (NHJAO^. Ca. — A white precipitate. Residue b. — Moisten with concentrated HCl and try coloration of flame. Ba. — Yellowish-green flame. Sr. — Scarlet flame. Confirmation Ba and Sr. — Fuse residue b with two to three pts. of soda in a pla- tinum capsule : treat fusion with boiling water, filter, reject filtrate, dissolve residue in acetic acid, add a few drops of HjS water, if it gives any precipitate, saturate with HjS and filter, and to filtrate add KjCr^O,. Ba = yellow precipate. Filter, and to filtrate add CaSO^ warm and let stand. Sr = white precipitate. PART III. DESCRIPTIVE MINERALOGY. CHAPTER XV. CHARACTERS OF MINERALS. All substances zvhich have not been formed by living grotvth be- long to the Mineral Kingdom of Nature ; and, in the broadest sense, mineralogy treats of all such substances. The magnitude of such a Science of Mineralogy has, however, forced an arbi- trary division. A MINERAL is now defined to be : a homogeneous substance, of definite chemical composition, found ready-made in nature, and not a product of life. Usually it will be a solid with a crystalline structure. Mineralogy in its arbitrarily limited sense considers the one thousand or so accepted minerals and the many thousands of doubtful species and varieties. Its primary purpose is the study of the elementary constitution of the minerals ; their chemical composition as revealed by analyses ; their molecular structure as revealed by crystalline form and by physical tests, and their origin and mode of formation as revealed by associated min- erals, the alterations which they undergo and their synthetic pro- duction. The consideration of artificial compounds is referred to Chemistry. Although the chemist's laboratory and Nature employ the same forces and produce some substances identical in all respects, the natural substances are usually not easily imitated because the im- portant element of long periods of time cannot be given to the manufacture of the substance. On the other hand most manu- factured compounds are too soluble and perishable to exist long as natural salts. 137 1 38 DESCRIPTIVE MINER A LOG Y. A ROCK is a mineral mass of fairly constant character for a con- siderable depth and area. It sometimes consists entirely of one mineral, much more frequently of two or more minerals, and may consist in part of organic remains. The resolution of these rocks into their component minerals and the study of these minerals belongs to Mineralogy. The study of these rocks, as such, is referred to Petrography and Geology. In elementary work in mineralogy, especially in a techni- cal course, the principal object is the acquisition of an ' eye knowledge' of the common and commercially important minerals so that they may be recognized at sight or determined rapidly by a few simple tests. This knowledge can be acquired only by hand- ling and testing both labelled and unlabelled specimens, and is best preceded by a thorough drill in the use of the blowpipe and a study of models and natural crystals. CRYSTALS OF MINERALS. Natural crystals are rarely ideal in shape and in examining them regard must be paid rather to the recurrence of similar groups of faces than to the actual position or size of the faces. Careful in- spection assisted by rough measurements of prominent angles with a hand goniometer will usually be sufficient to determine system, forms, and often species. The different crystals of any substance will usually show one or two predominating forms and if from the same locality will show an even greater constancy of habit, so that it is frequently possible to distinguish between crystals of different minerals closely alike in angle by the habit, that is the common association of faces. Regular Grouping of Crystals. The manner of the grouping of the crystals is sometimes a char- acter of importance. Frequently the grouping is irregular and apparently without law, as in Fig. 308 of Tyrolese epidote, but at other times there is an evident tendency to regular arrangement. Twinning has already been described, pp. 65-71, in which the cor- responding crystal axes are usually inclined to each other. A tendency to parallel arrangement of corresponding axes is also fre- quently observed which may be shown either by isolated crystals with their axes parallel, as in the case of the quartz crystals CHARACTERS OF MINERALS. 139 upon feldspar from Japan, shown in Fig. 309. Or the crystals may be united in parallel or approximately parallel position, as in the pyromorphite, from Nassau, Fig. 310. In certain instances the union of many crystals in approximately parallel position results in one larger crystal, either of the same form with slightly curved faces as in dolomite, Fig. 311, or of a different form, as in the formation of octahedral fluorite by 'the union of cubes. Fig. 309. Fig. 310. Regular groupings sometimes occurVhich are much less simple in character than the above, thus Dana describes * crystallized cop- FiG. 311. Fig. 312. Fig. 313. per occurring in groups like Fig. 313, com- posed of cubes each twinned parallel to an octahedral face and these twins united in par- allel position so as to form branches at sixty degrees to each other as shown in ideal form. Fig. 312. * Am. Journ. Sci., XXXII., p. 428, 1886. 140 DESCRIPTIVE MINERALOGY. Surface Irregularities. Etchings. — The perfectly smooth and plane surface is difficult to find, frequently the surfaces are more or less corroded by natural agencies, and many show natural etch figures similar to the arti- ficial etch figures described on p. 148. Striations. — Sometimes crystal faces are marked by fine paral- lel straight lines which are really fine "grooves" each bounded by two definite ciystal planes. They may result either from a contest between two crystal forms as in the case of the striations Fig. 314. Fig. 315. on the prism faces of quartz, Fig. 314, which are due to an alter- nate formation of prism and rhombohedron. At other times the striae are due to a repeated reversal or twinning of small individuals which together make the whole crystal. If individuals i, 3 and 5, are in normal position while the intermediate individuals 2, 4 and 6, are in reversed position, there will usually result reentantand salient angles. If the individuals are thin the reentrant angles be- come mere furrows or striations. Fig. 315 shows twinning stri- ations on a magnetite crystal from Port Henry, N. Y.* Ciu-ved Surfaces. — Crystals may appear curved because com- posed of individual smaller crystals only approximately parallel as Fig. 316. Fig. 317. in dolomite. Fig. 311, or siderite. Sometimes there results from this cause very peculiar shapes as in the worm-shaped crystal o *J. F. Kemp. CHARACTERS OF MINERALS. 141 corundum,* Fig. 316, which is composed of layers, each a hexag- onal pyramid cut off by the basal pinacoid. At other times the curving may be due to pressure after formation, which may be accompanied by a breaking of the crystal as in the tourmaline Fig. 317. Inclusions. — Foreign substances may be shut in a crystal dur- ing rapid solidification as in the case of drops of water or bubbles Fig 318. Fig. 319. of gas in quartz, or of sand in the crystals of calcite called Fon- tainebleau limestone, Fig. 318, which while retaining a form proper to calcite, contain sometimes as much as sixty per cent, of silica. At other times the inclusions are material which the process of crystallization has tried to eliminate from the crystal. In such a case the included material is apt to be definitely arranged as in the case of the magnetite in mica from Chandler's Hollow, Del.,t in which the magnetite is deposited on the cleavage planes of the mica and parallel to the mica prism of 1 20 degrees. This is also P'IG. 320. illustrated by the regular grouping of the purer white and less pure dark portions in chiastolite as shown in successive sections of a crystal in Fig 320. *H. Barvir, Beitrage zur Morphologic des Korund, Ann. K. K. Hofmuseums, VII. , 1892, p. 141. t Huntington, Am. J. Sci., XXXII., 301, 1886. 142 DESCRIPTIVE MINERALOGY. At times definite minerals are included such as Fig. 321. the little curved crystals of prochlorite (helminth), Fig. 321, frequently found in quartz and feldspar, or the magnetite in mica just mentioned, while at other times the inclusions may be microscopic crys- tals (microlites) or incipient crystals (crystallites) not easily identi- fied. CRYSTALLINE AGGREGATES. While the definite crystal is the simplest proof of that regular arragement of particles which is called a crystalline structure this structure usually exists even in masses which do not show a single crystal face. This is often proved by the fact that either the en- tire mass may be split (cleaved) parallel to definite planes or differ- ent portions may each be so split parallel to its own set of planes. Mineral masses which are not opaque if examined by polarized light, as explained later, produce effects upon the light entirely different from those produced by a substance with indefinitely ar- ranged particles, and in opaques masses the regular structure may be proved by other physical tests. Massive and Amorphous. All masses which do not show definite crystal faces are said to be massive, whether crystalline in structure or |not. If cleavage, polarized light and other tests fail to prove any crystalline struc- ture, the mineral is said to be amorphous. The number of min- erals accepted as amorphous is exceedingly small, but certain . varieties of minerals which cry.stallize may, from rapid cooling or other cause, be apparently amorphous. Columnar Structure. The structure is said to be columnar when the imperfectly formed crystals are relatively long in one direction and grouped. Fig. 322. Fig. 323. Fig. 324. CHARACTERS OF MINERALS. 143 Fig. 322 shows a columnar beiyl. The columns may be parallel or not. Bladed. — A variety of columnar in which the columns are flat- tened like a knife blade, as in cyanite. Fibrous. — A variety of columnar in which the columns are slen- der threads or filaments-, as in Fig. 323, of the serpentine asbestos of Quebec, Canada. Lamellar Structure. The structure is said to be lamellar when the imperfectly formed crystals appear as layers or plates, either straight or curved, as in the mineral talc. Fig. 324. Foliated. — A variety of lamellar, in which the plates separate easily. Micaceous. — A variety of lamellar in which the leaves can be obtained extremely thin, as in the micas. Granular Structures. The structure is said to be granular when the partially formed crystals , appear as aggregations of angular grains, which may be coarse or fine, as in the marbles. Impalpable. — A variety of granular in which the grains are in- visible to the unassisted eye. Imitative Shapes. Many terms are used, based upon a fancied resemblance to some natural object. The more important of these are : Reniform. — With the general shape of a kidney, as in hema- tite. Fig. 325. Fig. 325 Fig. 326. Botryoidal. — Having something of the appearance of a bunch of grapes, being made up of several globular individuals close to- gether, as in chalcedony, Fig. 326. Nodular — Occurring in separate rounded individual lumps or nodules. 144 DESCRIPTI VE MINER ALOG Y. Mammillary. — With low and broad rounded protuberances. Used for larger, flatter roundings than botryoidal. Oolitic. — Composed of small rounded grains Fig. 327. like the roe of a fish, as in varieties of calcite and hematite, or the hyalite from Japan, Fig. 327. Pisolitic. — Similar to oolitic, but the grains larger, the size of a pea. Stalactitic. — In hanging cones or cylinders like icicles, as in calcite or limonite. Fig. 328. Acicidar. — Rigid and slender like a needle. Fig. 328. Capillary.— Y\n& hke hair. Plumose. — Like a feather, as in a variety of mica from Minot, Me., Fig. 329. Sheaf like. — Resembling a sheaf of wheat, as in Fig. 650, of stilbite. Reticulated. — Crossing like the meshes of a net, as in Fig. 462, of stibnite. Fig. 330. Fig. 331. Arborescent or Dendritic. — Branching like a tree as in copper. Fig. 313, or pyrolusite. Fig. 330. CHARACTERS OF MINERALS. 145 Radiating. — Diverging from a common center, sometimes form- ing nearly complete spheres, as in pectolite from Paterson, Fig. 331. More frequently forming partial spheres, as shown in wavellite. Fig. 553, fig. 332. or pectolite of Bergen Hill, Fig. 602. Drusy. — Closely covered with minute crystals, giving a rough surface like sand- paper. Geode. — A hollow nodule lined with crystals, as in the quartz geode, Fig. 332. Incrustation. — A coating or crust. HARDNESS. The resistance of a smooth plane surface to abrasion is called its hardness, and is commonly recorded * in terms of a scale of ten common minerals selected by Mohs : 1. Talc, laminated. 6. Orthoclase, white cleavable. 2. Gypsum, crystallized. 7. Quartz, transparent. 3. Calcite, transparent. 8. Topaz, transparent. 4. Fluorite, crystalline. 9. Sapphire, cleavable. 5. Apatite, transparent. 10. Diamond. The following scale of Chapman gives about the same results : 1. Feels soft and greasy and is easily scratched by the finger- nail. 2. Just scratched by the finger-nail. 3. Scratches and is scratched by a copper coin. 4. Not scratched by copper, but does not scratch glass. 5. Just scratches glass ; easily scratched by a knife. 6. Scratches glass easily. Just scratched by a file. 7—10. Not scratched by a knife. A sharp corner of the substance tested is drawn across succes- sive members of the scale, from 10 down, until one is found to be scratched. Some inconspicuous but smooth surface of the sub- * In more exact testing the crystal may be moved on a little carriage under n fixed vertical cutting point and the pressure determined, which is necessary to produce a vis- ible scratch. Other methods are planing or boring v^ith a diamond splinter under con- stant pressure, and comparing the loss in weight for a given penetration or given number of movements. The loss of weight during grinding and the pressure necessary to pro- duce a permanent indentation or a crack have also been used as determinants of hard- ness. 146 DESCRIPTIVE MINERALOGY. stance is then selected and a sharp corner of the scratched standard mineral is moved back and forth several times on the same line a short distance ( ^ inch) across the surface. If the mineral is not scratched it is harder than the standard used, and the next higher on the scale should be tried in the same way. If the mineral is scratched it is of about the same hardness of the standard. Care must be taken to distinguish between a true scratch and the production of a "chalk" mark which rubs off Altered surfaces must be avoided. Or the knife may be used first, the hardness approximately judged by the ease with which it cuts the mineral and checked by the nearest member of the scale. If the knife does not scratch the specimen the harder members, 6 to lo, are used successively until one is found which scratches the mineral. TENACITY. A mineral is said to be Brittle, when it breaks to powder before a knife or hammer and cannot be shaved off in sHces. Sectile, when small shavings or slices can be shaved off which, however, crumble when hammered. Malleable, when slices can be shaved off which will flatten under the hammer. Elastic, when a thin plate will bend and then spring back to its original position when the bending force is removed. Flexible, when a thin plate will bend without breaking. CLEAVAGE. Many crystals break or cleave along more or less smooth plane surfaces in certain directions more readily than in other directions, and -it is found that these directions of cleavage are always par- allel to faces of forms in which the substance can crystallize. A cleavage face may usually be distinguished from a crj'stal face by its splintery character, and cleavage is often indicated by a pearly lustre on a face of the crystal parallel to the cleavage direction, the lustre being due to repeated light reflections from cleavage rifts. True cleavage is obtained with equal ease at any part of a crystal, and there is only a mechanical limit in the closeness of CHARACTERS OF MINERALS. 147 one cleavage to the next. The quarter undulation mica plate, ior instance, is a cleavage of mica of about i-i'i'^-^ '^'^- i" thickness. When cleavage is obtained parallel to one face of a crystal form it will be obtained with equal ease parallel to all faces of the form. For instance, galenite cleaves parallel to all planes of the cube, calcite in three directions parallel to the faces of a rhombohedron with diedral angles of 105° s', as shown in Fig- 333 and barite in two directions parallel Fig. 333. to the faces of a prism with an angle of 101° 37'- Cleavage may be obtained parallel to the faces of two or more separate crystal forms, for instance barite also cleaves parallel to the base, giving as a result of both cleavages a shape precisely that of Fig. 191. The cleavage angles are as exact as the angles between crys- tal faces, and as they can easily be obtained from any of the many possible crystal forms and frequently from the masses, the angles of cleavage as well as the ease of cleavage are useful char- acters in determination. Cleavage is, in general, limited to directions parallel to the simpler and more frequently occurring crystal forms. In the isometric system it is parallel to the cube, octahedron or dodecahe- dron. In the tetragonal system it is basal or prismatic and only rarely pyramidal. In the liexagonal system it is basal, prismatic or rhombohedral but rarely pyramidal. In the other systems the arbitrary selection of axes prevents a simple classification of the cleavages, but the selection usually makes one direction of cleavage pinacoidal and two of equal ease prismatic. The cleavage form is usually chosen as the unit form. Cleavage is said to be perfect or eminent when obtained with great ease, affording smooth, lustrous surfaces. Inferior degrees of ease of cleavage are called distinct, indistinct or imperfect, inter- rupted, in traces, difficult. Cleavage is usually obtained by placing the edge of a knife or small chisel upon the mineral parallel to the supposed direction of cleavage and striking a quick, sharp blow upon it with a hammer. In some instances the cleavage is produced by heating and sud- denly plunging the mineral in cold water. Frequently the cleavage is made apparent during the grinding of a thin section. 148 DESCRIPTIVE MINERALOGY. Sudden heat alone will often produce decrepitation and with easily cleavable minerals the fragments will be cleavage forms. FRACTURE. When the surface obtained by breaking is not a plane or a step- like aggregation of planes it is called a fracture and described as : Conchoidal, rounded and curved like a Fig- 334- shell, Fig. 334. E-uen, approximately plane. Uneven, rough and irregular. Hackly, with jagged sharp points and depressions as with metals. Splintery, with partially separated splinters or fibres. GLIDING PLANES. In a few minerals, -calcite, pyroxene, stibnite, halite, etc., it has been observed that pressure in certain directions will either produce a separation along a definite plane, which is not a true cleavage plane, or else will develop a twin structure (secondary twinning) with this " gliding plane " as the twin plane. If a cleavage of Iceland spar is placed, as in Fig. 335, with an edge ad of the larger angle resting upon a steady support and the Tig- 335- Fig. 336. blade of a knife is pressed steadily, as by a vise, at some point i of the opposite edge, the portion of the crystal between i and c will be slowly pushed into a new position of equilibrium as if by rotation about fghm until the new face gc' h and the old face gch make equal angles with fghm. CHARACTERS OF MINERALS. 149 PARTING. The planes along which a ghding has occurred may thereafter be planes of easy separation or Parting,'^ differing from true cleav- age, however, because in parting the easy separation is limited to the planes of actual gliding, while true cleavage is obtained with equal ease at all other parallel planes. Fig. 336 shows parting in pyroxene. PERCUSSION FIGURES. If a pin or a rod with a slightly rounded point is pressed against a firmly supported plate of mica and sharply tapped with a light hammer, three planes of easy separation wi be indicated by little cracks radiating f from riG^337- the point, Fig. 337, the most distinct of which is always parallel to the clino pinacoid, the others at an angle ;r thereto which is 53° to 56° in muscovite, 59° in lepidolite, 60" in biotite, 61° to 63° for phlogopite. In the same way on cube faces of halite a cross is developed with arms parallel to the diagonals of the face. On an octahedral face a three-rayed star is developed. ETCHING FIGURES. When a crystal or cleavage is attacked by any solvent the action proceeds with different velocities in crystallographically different directions, and if stopped before the solution has proceeded far, the crystal faces are found to be pitted with little cavities of definite shape. The absolute shape varies with many conditions; time, tempera- ture, solvent, ciystallographic orientation and chemical composition. The figures, whatever their shape, conform in symmetry to the class to which the crystal belongs, and are rarely forms common to several classes. They are alike on faces of the same crystal form and generally unlike on faces of different forms, and serve, therefore, as an important means (perhaps the most important) fo r determining the true grade of symmetry of a crystal and also for recognizing and distinguishing faces. * Similar planes of easy separation may be due to other causes, for instance, durin g the growth of a crystal the planes at certain intervals may be coated with dust or fin e lamellae of a foreign substance and later the crystal may grow further. This may be repeated several times, forming thus parallel planes of easy separation, e. g. , capped quartz. f By pressure alone three cracks diagonal to these are developed. ISO DESCRIPTIVE MINERALOGY. Fig. 338 shows the shape and direction of the etchings upon a cube of pyrite. These conform to the symmetry of the group of the diploid, p. 21. On the other hand the etchings upon a cube Fig. 338. Fig. 339. ^,;^^^^^£_J^ ■ ^ fl P. '^=^~-«.~« -E ^^ of fluorite, Fig. 339, show a higher symmetry corresponding to that of the hexoctahedral group, p. 1 2. The etchings of wulfenite. Fig. 341, show the mineral to belong to a class of lower symmetry than that suggested by the form. Fig. 340. Fig. 341. while the etchings of pyroxene, Fig. 340, like the form are sym- metrical to one plane. SPECIFIC GRAVITY. The specific gravity of a substance is its weight divided by the weight of an equal volume of distilled water. The Jolly balance, Fig. 342, is a simple piece of apparatus for obtaining the specific gravity of a solid. The lower scale pan is kept submerged ; three readings are made by noting the heights at which the index on the wire and its image in the graduated mirror coincide with the line of sight when the spiral comes to rest. CHARACTERS OF MINERALS. 151 Fig. 342. A. Instrument reading with nothing in either scale pan. B. Reading with mineral in upper scale pan. C. Reading with same fragment transferred to lower scale pan. B-A ^ . "5 -^ = Specific Gravity. In using an ordinary chemical balance the fragment is first weighed and then suspended from one scale pan, by a hair, or very fine plat- inum wire, in a glass of water and reweighed. The weight of platinum wire must be deducted. Specific Wt. in air Gravity ~ Wt. air — (Wt. water — Wt. wire)' Very porous minerals and powders are deter- mined by weighing in a little glass bottle the stopper of which ends in a fine tube. The min ■ eral is weighed and the bottle full of water is also weighed. The mineral is then added to the bottle and displaces its bulk of water, and the differenee between the weight and the sum of the other two weights is the weight of the displaced water. The material must be pure and for careful work should be boiled to expel air and allowed to cool in the water. Use of Heavy Liquids. There have been used for specific gravity determinations, but more especially for separating minerals of different specific gravities, a number of different liquids of which the best are : Thoulet Solution. — Mercuric iodide and potassium iodide, in the ratio of five parts to four by weight, are heated with a little water until a crystalline scum forms, then filtered. The maximum spe- cific gravity is nearly 3.2 and may be lowered by the addition of water to any desired point. Klein Solution. — Cadmium borotungstate with a maximum spe- cific gravity of 3.6. Braun's Solution. — Methylene iodide CHJ.^ with a maximum specific gravity of 3.32 which can be lowered by the addition of toluol. IS2 DESCRIPTIVE MINERALOGY. Penfield Solution. — Silver thallium nitrate which is liquid at 75° C, has a maximum specific gravity of over 4.5 which can be low- ered by the addition of hot water. In all of these the method of determining the specific gravity of a mineral, necessarily lighter than the liquid, is to add the diluent drop by drop until the mineral fragment will just float or if pushed in will stay wherever pushed. For determining the specific gravity of the liquid the most con- venient balance is that of Westphal, Fig. 343. The beam is gradu- ated in tenths and the weights A, B and C are respectively unit, 1(7 ^"d J-J-0-. Fig. 343. The balance is so constructed that when the thermometer float is suspended in distilled water at 15° C. a unit weight must be hung at the hook to obtain equilibrium. If then the test tube is nearly filled with the heavy liquid and weights added until equilibrium is secured the specific gravity is known. For instance in the figure the weights employed are : Unit weight at hook, value i.ooo Unit weight at sixth division, value 0.600 tV weight at sixth division, value. 0.060 TTU weight at ninth division, value 0.009 Specific gravity 1.669 CHARACTERS OF MINERALS. 153 For rough determinations a series of stoppered tubes containing solutions of known density is very convenient. TASTE. Some minerals have a decided taste which is usually either : Astringent, the taste of alum. Saline or Salty, the taste of common salt. Bitter, the taste of epsom salts. Alkaline, the taste of soda. Acid, the taste of sulphuric acid. Cooling, the taste of nitre. Pungent, the taste of sal-ammoniac. ODOR. Odors are rarely obtained from minerals, except by setting free some volatile constituent. The terms most used are : Garlic, the odor of garlic obtained by heating minerals contain- ing arsenic. Horseradish, the odor of decayed horseradish obtained from minerals containing selenium. Sulphurous, the odor obtained by heating sulphur or sulphides. Fetid, the odor obtained by dissolving sulphides in acid. Bituminous, the odor of bitumen. Argillaceous, obtained from serpentine and some allied minerals, after moistening with the breath. FEEL. Terms indicating the sense of touch are sometimes useful. Smooth, like celadonite or sepiolite. Soapy, like talc. Harsh or Meagre, like aluminite. Cold, distinguishes gems from glass. Adheres to tongue. CHAPTER XVI. OPTICAL CHARACTERS. LUSTRE. The lustre of a mineral is dependent principally upon refractive power but in part upon its transparency and structure. It may be called the kind of brilliancy or shine of the mineral. Metallic lustre is the lustre of metals. It is exhibited only by opaque minerals. Non-metallic lustre is exhibited by all transparent or trans- lucent minerals. It may be vitreous, adamantine, resinous, pearly, silky, greasy or waxy. Vitreous, the lustre of a fractured surface of glass or of quartz crystals. Adamantine^ the almost oily lustre of the uncut diamond or cerussite, exhibited by minerals of high idex of refraction. Resinous, the lustre of resin or sphalerite. Greasy, the lustre of oiled glass or elaeolite. Pearly, the lustre of the mother of pearl or of fohated talc. Common parallel to a very perfect cleavage. Silky, the lustre of silk or of satin spar, requires a fibrous struc- ture. Dull. Without lustre or shine of any kind. Kaolin is a good example. The prefi.x sub, as sub-metallic, sub-vitreous, is used to express an imperfect lustre of the kind. The words splendent, shining, glistening, glimmering and dull are terms of intensity dependent on the quantity of light reflected. Lustre should, when possible, be determined by a comparison with minerals of known lustre, and should always be observed on a fresh or unaltered surface. The degree or kind of lustre is always the same on like faces of the crystal, but may be different on unlike faces, as in the pearly basal plane of apophyllite and the vitreous prismatic faces. OPTICAL CHARACTERS. 155 COLOR. The color of minerals is one of their least definite characteristics, often varying with different specimens of the same species, and sometimes within the widest limits. Minerals of metaUic or sub- metallic lustre vary much less in color than non-metallic minerals and their color is, therefore, a more useful characteristic. It varies from tarnish and should be observed on fresh fracture. In describing color, white, gray, brown, black, blue, green, yel- low and red are used, often with prefixes, which suggest the color of some familiar object. These need no explanation. Play or Change of Colors. — A more or less rapid succession of prismatic colors appearing as the mineral is turned. Iridescence . — Prismatic colors, either from the interior of a min- eral, as from a thin film of air between cleavages ; or an external thin film due to some coating or alteration. Color is frequently due to a few hundredths of one per cent, of some organic or, more rarely, inorganic substance dissolved in the mineral, or it may be due to larger amounts of mechan- ically included foreign material. Tarnish. — A surface which has been exposed to the air or to moisture is often of different color from the fresh fracture. Opalescence. — A milky or pearly reflection, sometimes an effect of crystalline structure at other times due to fibi'ous inclusions. Asterism. — A star effect by reflected light as in the ruby or by transmitted light as in mica and due to structure planes or symmet- rically arranged inclusions. Phosphorescence. — The emission of light by a substance after exposure to light, heat, friction, mechanical force, or an electrical discharge. Fluorescence. — The emission of light during an exposure to light as when colorless fluorite colors a ray of sunlight pale violet. STREAK. The streak of a mineral is the color of its fine powder. It is usually obtained by rubbing the mineral on a piece of hard white material such as novaculite or unglazed porcelain, or it may be obtained less perfectly by scratching the mineral with a knife or file, or by finely pulverizing a fragment of the specimen. The streak often varies widely from the color of the mass and is nearly iS6 DESCRIPTIVE MINERALOGY. constant for any species. When not white it is a characteristic very useful in determination. TRANSLUCENCY. The translucency of a mineral is its capacity to transmit light. A mineral is said to be : Transparent, when objects can be seen through it with clearness. Subtransparent, when objects can be indistinctly seen through it. Translucent, when light passes through, as through thin porce- lain, not enough to distinguish objects. Subtranslucent, when only the thin edges permit any light to pass. Opaque, when no light appears to pass even through thin edges. THE OPTICAL CHARACTERS AS INDICATORS OF CRYSTALLINE STRUCTURE. Light is transmitted in straight lines by vibrations of a so-called "ether" which fills all space even between the particles of solids. REFRACTION. When a ray of light passes from one substance into another in which its velocity is different, the ray is bent or refracted. Index of Refraction. The amount of bending * is found to be such that whatever the ij sin z direction of the incident ray, — = —. that is the ratio between v^ sm p the sines of the angles of incidence and refraction is constant and is called the Index of Refraction of the second substance with respect to the first. Usually the index recorded is that of the second substance with respect to air. Denoting the velocity in air by v and the indices * The amount of bending may be graphically found by the construction of Snel- lius. Fig. 344, R^ is a sphere with radius the index of refraction of outer medium, R^, a sphere with radius the index of the crystal. Prolong JO to T. Draw TS parallel the normal ON, then is OS the refracted ray, and O Fthe corresponding reflected ray. In triangle OSY, OS : F= sin YS : sin OSY, but OS= n, Y= n^, O YS = OTY=-. i, and OSY^ p hence substituting sin i » : «j = sm p, or n =r «j sin p OPTICAL CHARACTERS. iS7 of the first and second substances with respect to air by n^ and n, we have «, ^ — and n^= — and substituting these values in the formula we have as the index of the second substance sin I n = n, -. ' sin f) Normal Incidence. There is no refraction for nor- inalincidence , for sin 2= o, hence sin p which, since « is a finite quantity, is only possible if /J = o. Refraction in Plane-Parallel Plates. Since most of the tests hereafter described are made upon plates of crystals with plane parallel sides, it is important to note that in such plates the ray emerging is parallel to the entering ray, for at entrance, Fig. 345, Fig. 345. sin t sin I. I n = «, — — and at emergence n. = n -. , ^ ,, ^ 1 .s,n n^ \cj^,^ 'sin n sm I whence — = —. — sin /5j but i^^ p ; hence i = Py TOTAL REFLECTION. When the index of refraction >i^ of the first substance is greater than n of the second substance, there is a so-called "critical" angle of incidence for which the angle of refraction is 90" ; that is, the refracted ray travels along the border surface. If ^ = 90°, sin /? = I ; hence, « = n^ sin i, or sin i = — . For any angle of incidence greater than this the light is totally reflected. 158 DESCRIPTIVE MINERALOGY. Fig. 346. DOUBLE REFRACTION. If an object is viewed through a moderately thick transparent cleavage rhomb of calcite,* it will appear to be double, as in Fig. 346. If such a cleavage is mounted so that it can be revolved about a hori- zontal axis normal to a vertical face, any light ray, IT, normally incident. Fig. 348, at the vertical face, is trans- mitted in the rhomb as two rays of es- sentially equal brightness (giving two images of any signal), and as the rhomb is turned about the axis one of these remains fixed in position, the other moves around the first. With single refraction and normal incidence the fixed image only would have been seen, hence this is called the ordinary and the movable image by contrast the extraordinary. Fig. 347. Fig. 348. t c That some peculiar change has taken place other than the di- vision of the one ray into two may be shown as follows : Let one of the two rays be shut off and the other viewed through a second calcite rhomb similarly mounted, this ray is again split into two rays, an ordinary and an extraordinary, but these are no longer of equal brightness, but wax and wane in turn, the sum of their intensities remaining constant. Planes of Vibration. The changes in intensity as the second rhomb is turned, corre- spond exactly to the assumption that the vibrations of common light *The property is common to all crystals except isometric, but calcite possesses it in a very marked degree. The double image can only be observed in a few substances, but the double refraction is better shown by the tests described later. OPTICAL CHARACTERS. 159 have been converted by the first calcite into two sets of straight-lined vibrations, at right angles to each other, the one parallel to a plane through ac and IT, Fig. 348, the other at right angles to this plane. The second calcite in the same way resolves the ' polar- ized' ray from the first into components varying in intensity ac- cording to the relative positions of the calcites. The vibrations of either the extraordinary or the ordinary ray might be parallel to ac, but we shall hereafter assume that the vibrations of the extraordinary ray are in a plane through the axis c, and those of the ordinary are at right angles to this plane. On this assumption, the so-called " Plane of Polarization " of Malus is at right angles to the plane of vibration ; that is, the plane of polarization of the ordinary ray is a plane through the axis c, and the plane of polarization of the extraordinary ray is at right angles to this. See Moses's Characters of Crystals, p. 98-100. Production of Plane Polarized Light. Plane polarized light may be produced from common light. {a) By reflection at a particular angle of incidence (tan i == «), the vibrations being at right angles to the plane of reflection (plane through incident and reflected ray). (/') By refraction through a series of parallel glass plates, each plate increasing the proportion of polarized light. In this case the vibrations are in the plane of reflection. In (rt) and (B) common light is always present. (<:) By double refraction and total reflection of one of the rays as in the so-called Nicol's prism, made from a cleavage of calcite with a length about twice its thickness, Fig. 349. The two small rhombic faces at 71° to the edge are ground away and replaced by faces at 68° to the edge. The prism is then cut through by a plane at right angles both to the new ter- minal faces and to the principal section. The parts are carefully polished and cemented by Canada balsam, the index of refrac- tion of which is 1.54 or about that of the extraordinary ray bd, which, therefore, passes through the balsam with but little change in direction ; the ordinary ray be, however, with an index of refraction of 1.658, being incident at an angle greater than its critical angle, is totally reflected. The vibration direction of the emerging light is parallel to the shorter diagonal of the face of the nicol, as shown by the arrow. i6o DESCRIPTIVE MINERALOGY. Fig. 3SO. A I I '. nfri . s ! ' • ' ' Mirk ((^ By double refraction and absorption. Certain substances absorb one ray much more rapidly than the other, hence thicknesses can be chosen for which one ray is totally absorbed, the other being partially transmitted with vibrations all in one plane. Tour- maline is often used, as in this mineral the ordinary ray is much the more rapidly absorbed. ' Polariscope for Parallel Light. The essentials of a polariscope for parallel light are shown in Fig- 3 SO- The mirror J/ sends parallel rays through the lower lens X, which concentrates them at the center of Sthe polarizer P; this point is also the focus of the ■^ equivalent upper lens X. On emergence from L III, the rays are again parallel, and undergo double re- ; I I ; fraction in the plate 5 of the substance. At what- ever angle the parallel rays are incident at the plate S, each ray, as AB, Fig. 3 5 1, is broken into two rays BC and BD, vibrating in planes at right angles to each other and following different paths in the plate. On emergence they follow parallel paths. Among the incident rays there are rays EG and EH such that the ordinary component of EII will emerge at D with the extraordinary of AB and the extraor- dinary component of EG will emerge at C with the ordinary of AB. That is from every point of the upper surface there will emerge the ordinary component of one ray and the extraordinary of another, and these rays will have travelled over slightly different paths in the plate with differ- ent velocities, their vibrations being at right angles to each other. To produce an interference effect, these vi- brations must be made parallel. A second polarizer^ A, called an analyzer is, therefore, placed in the path of these rays and resolves them into components, the vibrations of which are in and at right angles to the plane of vibra- tion of A, and only the former are transmitted. That is, there emerge from A rays advancing in the same line and with parallel vibrations. If these vibrations are alike in phase the intensity of the resultant ray will be proportionate to the square of the sum of their ampli- FiG. 351. OPTICAL CHARACTERS. i6i tudes, but if unlike in phase the intensity will be proportionate to the square of their difference. The usual apparatus employed for parallel light effects is a polar- izing (or petrographical) microscope. Fig. 352, shows the most re- cent simple type of Fuess. The lower nicol is raised or lowered Fig. 352. by the lever h, the objective is held in place by the clip k and is. centered by the screws c. The upper nicol N is thrown in or out by a horizontal motion and the telescope is raised or lowered. Convergent light effects are obtained with a high power ob- jective, by swinging a small con- vergent lens over the lower nicol, by a lever not shown, raising the nicol by h till it touches the lens, removing the eye piece and looking into the tube. "Extinction" and "Inter- ference " Between Crossed Nicols. When the planes of vibration of the polarizer /"and analyzer A are ' at right angles the arrangement ^ is usually described as " crossed nicols " without regard to the type of polarizer. It is evident that, with crossed nicols none of the light from the polarizer can pene- trate the analyzer and the field must be dark. If the doubly re- fracting crystal section S, Fig. 350, is introduced between the nicols, the field can only remain dark when the planes of vibration of the rays produced in the section coincide with the planes of vibration of the nicols. By rotating the stage of the microscope these so- called extinction directions are found by the darkening of the field. For all other positions the field will be illuminated by the compo- nents of the rays which penetrate the analyzer and this brighten- ing will be most intense for the diagonal positions. With monochromatic light the field will also be darkened, be- cause of destructive interference, whenever the faster of each pair 1 62 DESCRIPTIVE MINERALOGY. of rays is just one, two, three, etc., wave lengths, of the light used, ahead of the slower ray for. Fig. 353, if PP2.-a^diAA are the vibration directions of polarizer and analyzer and RR, D D those of the plate, then, since the vibrations are in the same phase, the components on /'/'will be Cr and Os which in turn yield com- ponents on A A of a and «j, equal and opposite. That is the light vibration is stopped. Fig. 353. Fig. 354. y^^ "^^r^^-oi , / i r' ^\ s, u^ f \ / \/ */ I V '■ / ^N^ * I J!^ On the contrary the field will be brightest when the faster ray is ahead \l, \l, -^l, etc., for in Fig. 354, since the vibrations are in opposite phase, the components of PP are Or and Os and yield as components on AA, Oa and Oa^ equal and in the same direction. A wedge of doubly refracting sub- stance, since the difference in path must increase with the thickness, will show, in monochromatic light, dark bands at reg- ular intervals, varying with the color of the light used and corresponding to differences between the emerging rays of one, two, three, etc., wave lengths. Fig- 355- mzzj 35 Interference Colors with White Light. The difference between the two rays or " Retarda- tion," A, as it is called, depends upon three factors : (a) the material, (d) the direction of transmission or orientation, ( u. Negative u ^ c. Strength of Double Refraction. The value of y—a is called the " strength of double refraction " or frequently the " double refraction " of the mineral and is an im- portant character. Measurements of Principal Indices of Refraction. The indices a and ;- of the fastest and slowest transmitted rays may be obtained by either of the methods described, on the follow- ing page, provided the direction of transmission, is at right angles to the optic axis. Two images (or limit lines) will be obtained, which may be in the field of the telescope at the same time, or may be wide apart. These may be distinguished by a nicol's prism, which transmits vibrations parallel to its shorter diagonal. The character results from c || f=+ or a || c = — . INTERFERENCE PHENOMENA BETWEEN CROSSED NICOLS WITH PARALLEL, POLARIZED LIGHT. The polarizing microscope is nearly always used, the cross hairs being parallel to the vibration planes of the polarizer and analyzer. Sections of the crystals are cut with parallel faces, normal to the desired direction of transmission, and are revolved upon the micro- scope stage. In sections normal to the optic axis the field remains dark throughout the entire rotation of the stage. In all other sections there is double refraction. The field is dark (extinction) at intervals of 90°, and brightest at positions diagonal to these, and with white light interference colors result as described, p. 16 1. * and c are used frequently to denote axes of elasticity in these directions. f Positive c parallel c means extraordinary is slower, hence has larger index. OPTICAL CHARACTERS. 167 The extinction directions in tetragonal and hexagonal crys- tals are either parallel or symmetrical to cleavage cracks and crys- tal outlines. Maximum darkness is not as easily judged as color, hence, if the field is make red or violet by a gypsum or a quartz test-plate, and the mineral inserted so as to only partly cover the field, it will, for the extinction positions, appear of the same color as the rest of the field. The Interference Color as a Test. The vibration directions of the faster and slower rays can be dis- tinguished by means of the interference colors developed with white light. The extinction directions in the section are found and placed in diagonal position, a test plate of some mineral, in which the vibra- tion directions have been distinguished and marked, is inserted be- tween the nicols (in a slot provided) with these directions also diago- nal. If the interference color is thereby made higher, as shown by the color chart, the vibration directions of the corresponding rays are parallel ; if the color is lowered, the corresponding directions of vibration are crossed. The test plates most used are : Quarter Undulation Mica Plate. — A thin sheet of mica on which is marked C, the vibration direction of the slower ray, which in mica is the line joining the optic axes. The thickness chosen corresponds to a 140 fifi. which is J/l for a medium yellow light. Gypsum red of First Order. — A thin cleavage of gypsum on which is usually marked a, the vibration direction of the faster ray. The thickness chosen corresponds to an interference colo^ of red of first order, or say i6o/i/i, which is essentially /i for a medium yellow. The approximate retardation or difference in phase of the two rays may also be measured by placing the extinction directions in diagonal position and inserting a "wedge" with the corresponding vibration directions crossed and running the color down to black. The wedges most used are : Quartz Wedge. — A thin wedge of quartz, cut so that one face is exactly parallel to the optic axis. The length of the wedge is parallel to the optic axis, and as quartz is positive this direction is c, the vibration direction of the slower ray. The v-Federow Mica Wedge. — Fifteen quarter undulation mica plates super- posed in equivalent position, but each about 2 mm. shorter than the one beneath it. The mica wedge inserted with corresponding vibration directions crossed over those of the section will for each interposed plate reduce A J by 140 m. To render the field dark will require = n plates. ■' T^ ' ' 140 Conversely n. x 140 = ^, in which n is determined by count. 1 68 DESCRIPTIVE MINERALOGY. Fig. 359. The quartz wedge similarly used will give an approximate value by counting the number of times the original color reappears, if n times, then is the color a red, blue, green, etc., of « + i order, for which the value may be looked up in a chart. The approximate strength of the double refraction will result by dividing the value of d by the thickness of the section in millionths of a millimeter. INTERFERENCE PHENOMENA BETWEEN CROSSED NICOLS WITH CONVERGENT LIGHT. In sections normal to the optic axis with monochromatic light there will always appear a dark cross, the arms of which intersect in the center of the field, and remain parallel to the vibration planes of the nicols during rotation of the section. Any ray will vibrate either in or normal to a plane through the ray and the optic axis. Hence the rays transmitted parallel to the vibration planes of the crossed nicols have their vibrations in these planes and are totally extinguished. As the stage is rotated successive rays come into these positions maintain- ing the sariie effect. Destructive interference will take place at those points at which the " Retardation A " is equal to one, two or three, etc.,' wave lengths of the light used, p. i6i. Therefore, because the optic axis is an axis of isotropy, there will be dark circular rings around the center of the cross at distances apart varying with the crystal and the thickness of the crystal section. In sections of the same mineral the thicker the section the closer the rings, while in sections of different minerals but equal thickness the greater the value of ;- — a the closer the rings. With white light the rings become rings of color corresponding to the Newton colors. Determination of Optical Character of Crystal. The Mica Test Plate inserted above a section normal to the optic axis with its direction c diagonal to the nicols will destroy the * A. J. Moses Characters of Crystals, p. 103. OPTICAL CHARACTERS. 169 black cross and break the rings into four quadrants, the relative effects in positive and negative crystals being shown in Figs. 360, 361. . The corresponding signs + and — are suggested by the relative positions of the dark flecks and the arrow showing the direction c of the test plate. When the rings are almost or quite out of the field it is more convenient to insert a gypsum (red of first order) plate with its direction a in diagonal position, the effect being that " blue quadrants " correspond in position to the black flecks. This de- termination must be made in white light. UNIAXIAL CIRCULARLY POLARIZING CRYSTALS. Certain hexagonal and tetragonal crystals, notably those of quartz, are circularly polarizing in the direction of the optic axis though in other respects they act. optically- like other uniaxial crystals. With Parallel Monochromatic Light and Crossed Nicols. In sections normal to the optic axis the light is not extin- guished until the analyzer has been turned a definite number of degrees dependent upon the thickness of the section and the wave length. The direction in which it is necessary to turn the analyzer to change violet into red is the so-called direction of rotation. With Parallel White Light and Crossed Nicols. . The shorter the wave length the greater the rotation, that is the different colors are dispersed and on emergence vibrate in different planes. As the analyzer is turned its plane of vibration is succes- sively at right angles to the planes of vibration of the different colors. That is, at any time only one color is shut out completely 170 DESCRIPTIVE MINERALOGY. and the rest in varying degree. The color with vibrations most nearly parallel to the vibration planes of the analyzer will be least shut out and will determine the predominating tint in the resultant color. Fig. 362 shows the rotations produced by a quartz plate of 3.75 mm. thickness. The vibration plane of yellow is; for this thick- ness, at right angles to PS, the vibration plane of the incident light. Fig. 362. Fig. 363. With Convergent Light and Crossed Nicols. In sections normal to the optic axis with monochromatic light, sections not too thin will show the dark cross with arms parallel to the vibration planes of the nicols. The arms will be either indis- tinct near the center, or in thicker sections will not reach the center, Fig. 363. The first ring will be some distance out, beyond this there will appear the alternate dark and light rings. With white light the central circle will have the color tint which is obtained over the entire field when parallel light is used. The Direction of Rotation may be ascertained in convergent light by: (a) The widening of the arcs when the analyzer is turned in the direction of rotation. (b) A quarter undulation mica plate inserted diagonally above the plate converts the rings and cross into two interwound spirals, which start near the center and wind in the direction of rotation,* * A plate of left and another of right-handed substance give a fourfold spiral in which the direction of winding conforms to the lower plate. OPTICAL CHARACTERS. 171 Fig. 364, Right; Fig. 365 Left. If the mica is placed below the plate the spirals are reversed. Fig. 364. Fig. 365. OPTICALLY BIAXIAL CRYSTALS. ORTHORHOMBIC, MONOCLINIC AND TRICLINIC CRYSTALS. In orthorhombic, monoclinic or triclinic crystals by measure- ment of the indices of refraction with light of any definite wave- length (monochromatic light), two directions of single refraction are found, and these directions, from analogy with the uniaxial, are called the " Optic axes "for light of that wave-length. In all other directions there is double refraction and the directions of the optic axes are not the same when light of a different color is used. Optical Principal Sections and Principal Vibration Directions. If, with any one light, the indices of refraction are determined for all directions, the resultant values are found to always be sym- metrical to three planes at right angles to each other which inter- sect in the vibration directions of the fastest and slowest rays, the third intersection being the vibration direction of a ray of some intermediate velocity. These planes of symmetry are called Optical principal sections and their intersections are called Principal vibration directions, and may be designated by a, 6 and c, in which a is the vibration direc- tion of the fastest transmitted ray, c the vibration direction of the slowest transmitted ray, b the vibration direction of the ray trans- 172 DESCRIPTIVE MINERALOGY. mitted at right angles to the other two rays and with some inter- mediate velocity. Principal Indices of Refraction. The directions of vibration are at right agles to the direction of transmission. The indices of refraction of the three rays with vibration directions a, b, c, are denoted by a, /? and ;-, and called the principal indices of refraction. Then evidently a < /3 < ;-, and also there will be transmitted in the direction a two rays with vibration directions b and c and indices of refraction /? and ;-. Similarly in the direction b there will be transmitted two rays with vibration directions a and c and indices a and y ; and in the direction of c, two rays with vibration directions b and a and in- dices /? and a. Optically Positive and Negative Crystals. The optic axes or directions of single refraction lie always in the plane of a c. According to the angle which they make with a and C the following division is made : If c bisects the acute angle between the optic axes the crystal is said to be optically /o«V«w. This is usually expressed : +, Bx^ = c. If a bisects the acute angle between the optic axes the crystal is said to be optically negative. This is expressed : — , Bx^ =a. Measurement of the Principal Indices of Refraction. The Prism Method. In biaxial crystals the direction of transmission for minimum deviation will yield a principal index of refraction, only when it is normal to one of the directions a, b or c, and at least two differently oriented prisms will be necessary to secure the three principal indices. By the total reflection* method all three indices can be obtained from any plane surface parallel to any one of a, b or c. INTERFERENCE PHENOMENA BETWEEN CROSSED NICOLS WITH PARALLEL POLARIZED LIGHT. In sections normal to an optic axis no extinction will take place, but with monochromatic light the field will maintain a uniform brightness during rotation of the stage and with white light there may be even a color tint. *A. J. Moses, Character of Crystals, p. 146, OPTICAL CHARACTERS. 173 In all otlier sections the field is dark every 90° and is illuminated for all other positions and most brilliantly in the diagonal positions. If white light is used interference colors result as described, p. 161. Extinction Directions. The Extinction Directions are determined as described, p. 166. See also under distinctions between orthorhombic, monochnic and triclinic, p. 176. Interference Colors. The Interference colors with white light are essentially as de- scribed, p. 161, though with marked "divergence" they are modi- fied by color tints due to the partial or complete extinction of certain colors. The other determinations with parallel light are exactly as de- scribed under uniaxial crystals. Interference Phenomena Between Crossed Nicols with Convergent Polarized Light. In sections cut normal to either a or c, that is normal to a bisectrix of the angle between the optic axes, with monochromatic light An interference figure results, the field being dark throughout an entire revolution for all points at which — = i, 2, 3, etc., p. 16 1, / and brightest for — = |-, |-, |-, etc. The points of emergency of Fig. 366. the optic axes will therefore be dark, since — = o, and the points corresponding to— ^ i will together form a ring around each axis and similarly for values of 2, 3, 4, etc., until the pair corresponding most nearly to the value —for the centre of the field unite at or A near the centre to a cross loop or figure eight around both axes and 174 DESCRIPTIVE MINERALOGY. subsequent rings form lemniscates around this as in Fig. 366. There will be no change in shape during rotation of the stage. If— for the centre is less than unity even the first ring must surround both axes. With sections of the same mineral the thicker the section the closer together will be the rings, and with sections of different min- erals but equal thickness the greater the difference between a and ;- the closer together the rings. Corresponding to the dark cross, p. 167, and due to the same cause there will be a sharp dark band joining the axes and another some- what thicker lighter band at right angles to the first and midway be- tween the axes, but they differ from the uniaxial cross in that as the stage is rotated the straight bars change into a hyperbola, Fig. 367, the branches of which rotate in the opposite direction to the stage, the convex side always toward the other branch. With white light the light and dark rings are replaced by inter- ference colors. Determination of Optical Character of a Crystal. In a section normal to the acute bisectrix* the interference fig- ure is placed with the line joining the axial points in diagonal position, as in Fig. 367, and the quartz wedge is gradually in- serted with the direction c parallel to this line. If the crystal is positive the rings around each axis will expand, moving toward the centre and corresponding rings will merge in one curve. If the crystal is negative the rings will contract and increase in number, the change increasing with the thickness of wedge inter- posed. In a section normal to the obtuse bisectrix these results are all reversed. * To determine the acute bisectrix it may be necessary to first measure the axial angle. Ordinarily the interference figure in a section normal to the obtuse bisectrix will not come within the limits of the field. Fig. 367. OPTICAL CHARACTERS. 175 In crystals with a small axial angle the mica or gypsum plate may be used as described, p. 167. Determination of the Angle Between the Optic Axes. A section cut normal to the acute bisectrix is held at P, Fig. 368, between the lenses of a horizontal polariscope. The vibration directions^of the nicols of the polariscope are crossed at 45" to the horizon, so that when the line connecting the axial points is horizontal the interference figure will show the hyperbola and not the cross. The section must be centred so that a line in it is the axis of revolution; and so that the axial points of the interference figure remain on the horizontal cross hair during revolution. Fig. 368. The crystal is then revolved by the horizontal plate until the two arms 'of the interference hyperbola are successively made tangent to the vertical cross-hair, the positions being read on the plate. The difference between the two readings is the apparent angle 2E, and this is frequently the angle recorded. It is always larger than the true angle 2 V. 176 DESCRIPTIVE MINERALOGY. Fig. 368 shows the newer type of so called Universal Apparatus of Fuess. The centring device is precisely that described under the Fuess goniometer and may be inserted either as in the figure or in- verted. In the latter position it forms with the telescopes F^ and 7^ the equivalent of the Fuess goniometer, Fig. 273. When used for axial measurements, the crystal stand is replaced by the pincers P which clip the crystal plate. The optical por- tion inserted at A and A^ is the same Norremberg arrangement of nicols and lenses which is shown in Fig. 357, but turned so* that the vibration directions of the nicols cross at 45° to the horizon. To find the True Angle from the Apparent Angle. When the middle principal index /? is known 2 V may be deter- sin E mined by the relation sin F= — ^ — . When /? is not known a second measurement may be made o the apparent angle in a plate normal to the obtuse bisectix. De- noting this by 2 ^' the relation is tan V=^ —. — pr, . *= ' sm E' Approximate Measurement of the Axial Angle. The axial angle 2 V may be determined in any suitably equipped microscope or polariscope by measuring the distance d from the centre to either hyperbola, or the average of the two distances, with a micrometer eye-piece. Then sin E= -^, or sin F=7;--?.,in which C is a constant for the same system of lenses and is deter- mined once for all with a crystal of known axial angle. For instance if in a mica 2E= 91 ° 50' and ^= 41.5 divisions on the scale, then C=—. — f^= '57.15^ for that combination of lenses. OPTICAL DISTINCTIONS BETWEEN ORTHORHOMBIC, MONO- CLINIC AND TRICLINIC CRYSTALS. In Orthorhombic Crystals the crystallographic axes are always principal vibration directions and the axial planes are optical prin- cipal sections for all colors. It is therefore possible to recognize the system of an orthorhom- bic crystal by : («) The extinction directions which will always be parallel or symrnetrical to crystallographic edges, cleavage cracks, etc. In OPTICAL CHARACTERS. 177 pinacoidal faces the vibration direction will be parallel to the crystal axes. ((5) The interference figure ohtahned in sections parallel to two of the three pinacoids will be like Fig. 367, and if the figures so obtained are viewed in white light the color distribution will be symmetrical both to the line joining the optic axes and to the line through the centre at right angles thereto. In Monoclinic Crystals the ortho axis b is always a principal vi- bration direction and the clinopinacoid is an optical principal sec- tion for all colors, the other two principal vibration directions lie in the clinopinacoid, but vary in position with the wave-length. It is therefore possible to recognize the .system of a monoclinic crystal by : {a) The extinction directions which are parallel or symmetrical to edges, cleavages, etc., only when the section is parallel to the ortho axis b, but in all other zones are oblique. (3) The interference figure sxmXzx to Fig. 367 will be found either in the section parallel to the clino pinacoid or in one of two sec- tions normal to this. In luhite light the distribution of color of this figure will never be symmetrical to two lines as in the ortho- rhombic, but will be symmetrical either to the line joining the axial points, or to the line normal to these, or to the central point. In triclinic crystals there is no essential relation between crys- tallographic axes and principal vibration directions, all extinctions are oblique and in white light, the distribution of color in the in- terference figure is entirely without symmetry. ABSORPTION AND PLEOCHROISM. Light during transmission through a crystal is in part absorbed and in most instances diminishes steadily in intensity as the dis- tance traversed increases. With white light the different component colors are absorbed at different rates, giving color tints due to the combination of the remaining colors. In Isometric Crystals. A section of any given thickness will transmit the same color tint whatever the direction in which the crystal may be cut. 178 DESCRIPTIVE MINERALOGY. In Doubly Refracting Crystals. In all doubly refracting crystals the ordinary and extraordinary rays transmitted in any given direction may be differently absorbed and with white light the color tints may be different ; not only for the ordinary and extraordinary rays transmitted in one direction but also for different directions. Usually the ordinary and extraordinary rays may be viewed separately by means of a polarizing microscope with the analyzer out. The color varies as the stage is turned and the maximum color differences are obtained when the extinction directions coin- cide with the vibration plane of the polarizer. The colors of the ordinary and extraordinary rays may be con- trasted s\A& by side bymeans of a "dichroscope" consisting, Fig. 369, Fig. 369. of a rhomb ofcalcite in which ab and cd are the short diagonals of opposite faces. To these faces glass wedges aeb, dfc are cemented and the whole encased. The section is placed at P and the light from the substance passes through a rectangular orifice, a double image of which is seen by the eye at E. In Tetragonal and Hexagonal Crystals with the Polarizing Microscope. In sections normal to the opic axis the color is constant for all positions of the stage. In sections parallel to the opic axis. If the extinction direction parallel to the optic axis is placed first parallel then at right angles to the short diagonal of the polarizer there will be seen first the extraordinary, second the ordinary. In all other sections the extraordinary will be found to approach the constant tint of the ordinary as the sections become more nearly perpendicular to the optic axis. OPTICAL CHARACTERS. 179 In Optically Biaxial Crystals : In orthorhombic crystals the directions of the absorption axes coincide for all colors with the directions of crystal axes and the principal vibration directions a, b and c. In monoclinic crystals one absorption axis is parallel to the crystal axis b, therefore to one of a, b or c, the other axes lie in the clinopinacoid, but, for any color, may or may not coincide with a b and c for that color. In triclinic crystals no coincidence is essential. Although subject to many exceptions, the law of Babinet is generally correct that "the slower transmitted ray is the more ab- sorbed." CHAPTER XVIII. THE THERMAL, MAGNETIC AND ELECTRICAL CHARACTERS. THE THERMAL CHARACTERS. Transmission of Heat Rays. Heat rays are subject to the same laws as light rays and differ principally in their greater wave length. They may be reflected, refracted, doubly refracted, polarized and absorbed. It is possible, though difficult, to determine experimentally a series of constants for crystals with respect to these invisible rays, but their discussion belongs rather to physics than to mineralogy. Surface Conductivity. The relative surface conductivies may be obtained when the previously cleaned and polished section is breathed upon, quickly touched by a very hot metal point normally applied, and instantly dusted with lycopodium powder. The section is then turned up- side down and tapped carefully, when the powder falls from where the moisture film had been evaporated, but adheres elsewhere, giving a sharply outlined figure. The entire operation should take less than three seconds. Or the section may be coated with a mixture of three parts elaidic acid and one part wax, and brought into contact with a heated metal point, and a constant temperature maintained until the wax has melted far enough from the point of application of the heat. The boundary of the melted patch then shows the distances which the heat has been transmitted, and is visible after cooling as a ridge which is always an ellipse or circle. In singly refracting crystals {isometric) all sections yield circles. In optically unaxial crystals {tetragonal or hexagonal') basal sec- tions yield circles, but all other sections yield ellipses which be- come more eccentric as the section becomes more nearly parallel to the optic axis. In optically biaxial crystals the curves are all ellipses. In orthorhombic crystals the axes of the ellipse obtained in any axial THERMAL CHARACTERS. I8I plane are parallel to the crystal axes therein. In monoclinic crys- tals the major and minor axes of the isothermal curves should coincide with crystal axes in any plane parallel to b. In triclinic crystals there will be no essential or probable paralellism of crystal axes and axes of ellipses in any section. Expansion. When a crystal is uniformly heated, directions crystallographic- ally alike expand in the same proportion, but directions unlike do not. 1° Isometric Crystals. The rate of expansion is the same for all directions. 2" Tetragonal and Hexagonal Crystals. The rate of expansion is the same for all directions equally inclined to the axis c ; is either a maximum or a minimum'parallel to c, and varies regularly from this to directions at right angles. 3° Orthorhombic Monoclinic and Triclinic Crystals. The direc- tions of maximum and minimum expansion are at right angles. Orthorhombic, the direction coincides with two of the crystal axes. Monoclinic, one direction ftiay coincide with b, or both lie in the clino pinacoid. Triclinic, the axes have no fixed positions relative to crystal. The increase in expansion may be accurately measured for any direction by the method of Fizeau, as follows : In Fig. 370 C is a plane parallel plate of the crystal, about 10 mm. thick, which rests upon the steel plate T Three screws pass through T and support the glass plate P, which tapers slightly. By adjusting the screws so that the upper surface is horizontal a thin wedge-like film of air is left between the upper surface of the sub- stance and the lower surface of the glass. By a suitable arrangement, rays of monochromatic light strike the apparatus normally. Rays incident at the upper surface of the crystal and the lower surface of the glass wedge interfere on reflec- tion producing parallel dark bands wherever the thickness of the /. The distance between two adjacent bands is wedge IS \^ ' 2 1 82 DESCRIPTIVE MINERALOGY. therefore a function of a wave-length of the light used and is meas- ured by a screw micrometer. When the apparatus is uniformly heated the crystal plate and the interference apparatus both expand and the interference bands change in distance apart. From this change and from the pre- viously determined effect of the expansion of the metal stand the change due to the expansion of the crystal is calculated. Tutton has recently described an improvement of this apparatus in which the expansion of the metal stand is compensated by that of a cylinder of aluminum. Change o*f Crystal Angles produced by Expansion. A crystal of the isometric system when uniformly heated ex- pands uniformly without change of angles. In all other systems the expansion varies with the direction and certain angles are changed (sometimes several minutes for ioo° temperature altera- tion. For instance, the calcite rhombohedron angle is lessened 8' 37".) The zone relations and indices are never changed. These changes may be measured with accurate goniometers and the relative expansions calculated. Change of Optical Characters produced by Expansion. The expansion of a crystal changes the velocity of light trans- mission and therefore the indices of refraction for different directions. With isometric crystals the index may become either larger or smaller. With tetragonal and hexagonal crystals the principal indices of refraction ;- and a may alter unequally and not neces- sarily in the same direction. The interference figure will also alter, the rings contracting or expanding according to the change in y—a, and for a particular temperature, when this difference is zero, will dis- appear. In orthorhombic, monoclinic and Fig. 371. triclinic crystals the interference fig- ure may undergo even more striking changes. For instance, Fig. 371 represents such a series in say gypsum with yellow light for which at 20° C. the axial angle is 92° (Fig. a), at 100° C. is reduced to 51° (Fig. b), at 134° C. is zero (Fig. c), and for still higher temperatures the optic axes pass into a plane at right angles to their former position (Figs, d and e). MAGNETIC CHARACTERS. l8S THE MAGNETIC CHARACTERS. Only a few minerals noticeably disturb a magnetic needle or are attracted by a steel magnet. Occasionally these minerals will them- selves act as magnets. Para- and Diamagnetism. All substances are either attracted or repelled in some degree in the field of a strong electromagnet. If attracted they are said to be "paramagnetic" or "magnetic" ; if repelled they are " dia- magnetic." If a rod of any substance is suspended by a fiber so as to swing freely horizontally between the vertical poles of an electromagnet, the rod, if paramagnetic, is pulled into "axial" position with its ends as near the poles of the magnet as possible, and, if diamag- netic, is pushed into an "equatorial" position with its ends as far from the magnetic poles as possible. Crystals are more strongly magnetized in certain directions than in others, and the para- or diamagnetism is judged by hanging a thin glass tube, filled with powder of the substance, between the magnetic poles, the particles of the powder, having all possible orientations, eliminate all effect of direction. Relative Induction in Different Directions in a Crystal. The para- or diamagnetism is determined as described. A cube of the crystal is then suspended by a silk fibre between the poles of an electromagnet and with its three rectangular axes successively vertical. If, for instance, in a diamagnetic substance for the three suspensions, one of the axes twice assumes the equatorial position, then this is the direction of greatest magnetization, but if the sub- stance is paramagnetic the axis which twice assumes an «jf/«/ posi- tion is the direction of greatest magnetization. The relations cannot yet be said to be well understood as very few minerals have been thoroughly tested. ELECTRICAL CHARACTERS. Frictional Electricity. All minerals are electrified by friction but the positive or negative character may vary in different varieties of the same species and even with different conditions in the same specimen. If a light, horizontally-balanced needle terminating in small balls is electrified, either positively by bringing near a rod of electrified 1 84 DESCRIPTIVE MINERALOGY. sealing wax, or negatively by touching with the rod, an electrified mineral will attract or repel the needle according as it has opposite or similar electricity. Electrical Conductivity. If a prism of known dimensions is introduced into a direct weak current, the strength of which is varied by resistances and the deviation observed in a galvanometer, results will be obtained which vary for different minerals between very wide limits and appear to be dependent upon the constitution of the chemical molecule rather than upon the crystalline structure. A certain dependence upon crystallographic direction has nevertheless, been observed in a few substances.* All minerals conduct to some extent, but practically, conductivity may be considered to be limited to the metals ; some metalloids ; most sulphides, tellurides, selenides, bismuthides, arsenides and an- timonides, some of the oxides ; and, at higher temperature, a few haloids. Thermo-electricity. If a metallic circuit is made by soldering together one end of each of two rods of different metals and connecting the other ends by wire, heating or cooling the junction will develop an electric current the strength of which will depend upon the change of temperature and upon the metals used. A series may be made based upon the strength and direction of the current. Among metals the series extends from bismuth at the positive end to selenium at the negative end. The position of minerals in the series may be practically determined. In crystals, moreover, a thermo-electric current is developed by coupling two rods cut from different directions in the same crystal, or by inserting a single rod in a metallic circuit and either heating the ends while the sides are kept at a uniform temperature or by the reverse proceeding. Dielectric Induction. A crystal suspended in an electrostatic field develops an electric polarity, and the crystal tends to assume a position in which the lines of force and the direction of maximum induction are parallel. * Uber das Leitungsvermogen der Mineralien fiir Elektricitat. F. Beijerinck, Neues Jahrb. Min., Beil, Bd. XL, 403, 1896-7. Also Wortman, Mem. de la Soc. d. hist. Nat. de Geneve, XII., 1853. ELECTRICAL CHARACTERS. 185 In the experiments of Root * circular plates of tourmaline, quartz, calcite, aragonite and topaz about 10— 11 mm. in diameter and cut parallel to the optic axis, were attached by a little drop of glue to a silk fibre and suspended between the vertical plates of a condenser charged by a rapidly alternating current. The vibra- tion thereby produced in the plate was reflected to a telescope two meters distant, and its period determined both when the direction of maximum induction was vertical and horizontal. The quotient of the former by the latter gave a basis of comparison. Pyroelectricity and Piezoelectricity. Whenever the volume of a crystal is altered either by a tempera- ture change or by mechanical pressure a portion of the heat energy or mechanical energy may be converted into electric en- ergy, which, in poorly conducting crystals, will be frequently mani- fested by the accumulation of positive and negative charges at different points or poles. In Pyroelectricity a temperature change of at least 70° to 80° C. is desirable. Usually the crystal is heatedf in an air bath to a uniform temperature, then drawn quickly once or twice through an alcohol flame and allowed to cool. During the cooling of the crystal the positive charges collect at the so-called antilogue poles, and the negative charges at the ana- logue poles,! ^i^"^ vivsY be distinguished by their effect on other electrified bodies. For instance, a cat's hair rubbed between the fingers becomes positively electrified and is attracted by the analo- gous pole and repelled by the antilogous pole. Or the positive and negative poles may be distinguished by blowing upon the cooling crystal a fine well dried § mixture of equal parts of powdered sulphur and red oxide of lead. The noz- zle of the bellows is covered by a muslin net and in the passage through the sulphur is negatively electrified and is attracted by the positive poles coloring them yellow while the minium is posi- tively electrified and is caught by the negative poles colonng them red. The dust should- fall evenly and the bellows be held far enough away to prevent direct action of the blast. * Poggendorf s Annalen, CLVIII., i, 425, 1876. f If heating injures the crystal it may be cooled from room temperature by a freezing mixture. J With rising temperature these are reversed. \ Dry over H^SO^ in a vessel from which the air has been partially exhausted. 1 86 DESCRIPTIVE MINERALOGY. Figs. 372, 373 and 374 show crystal of tourmaline, calamine and boracite respectively, the darker dotted portions represent- ing the accumulation of minium at the analogue poles and the hatched portions the accumulations of sulphur at the antilogue poles. ' If the crystals had been dusted during the heating, the analogue poles would have been coated with sulphur and the antilogue poles with minium. In Piezoelectricity the charges are developed by pressure, for instance, calcite pressed between the fingers becomes positively Fig. 373. Fig. 374. electrified, tourmaline compressed in the direction of the vertical axis develops a positive charge at the antilogue end and a nega- tive charge at the analogue end or precisely the charges which would result from cooling a heated crystal. The charges are detected in the same way as the pyroelectric charges. CHAPTER XIX. CHEMICAL COMPOSITION AND REACTIONS. As has already been stated, minerals are distinguished from rocks by something of regularity in their chemical structure. While all minerals may be best considered as derived from definite chemical types they are, however, very far from being of definite and invariable composition and it is often difficult to represent the results of analysis by an exact formula. This is readily under- stood when the laws of isomorphism and the conditions underly- ing the formation of minerals are studied. Isomorphism. Certain chemical substances, having an equal number of atoms in their molecules and presenting a close resemblance in their re- actions, crystallize in forms which are either identical or very closely related. Such isomorphic substances cannot be separated from each other by ordinary crystallization as the analogous com- pounds crystallize together, and the crystals formed show by analy- sis the most varied quantitative proportions of the isomorphic sub- stances present in the liquid. Most minerals are isomorphic mixtures. They have, as a rule, been formed by crystallization either from solution or from fusion. Some, as limonite, have been formed by a process of sedimentation but such are uncrystallized, and are generally quite impure. Others are the results of alteration from atmospheric agencies and fre- quently contain in the same specimen the original mineral and its alteration product. Whenever a mineral has crystallized from solution or from fu- sion it is always more or less modified by the elements which may be present and which are foreign to its own typical structure. Three cases present themselves : I. If the liquid contains no other substance than the compound of which the mineral is made then it crystallizes out in a state of purity and is as definite in its composition as any compound made in the laboratory. 1 88 DESCRIPTIVE MINERALOGY. 2. If the liquid contains several other substances but none which is isomorphous with the compound of which the mineral is made, it may crystallize in all degrees of purity, tending always to form crystals of definite composition but the composition of the mass varying with the degree with which the liquid is saturated with the foreign substances. This gives rise usually to a series of frac- tional crystallizations especially apparent in beds of rock salt or in mica and orthoclase veins. If the substances are in solution that one is first deposited whose saturation point is first reached by any process of concentration, the others following in their respective order. Where the case is one of fusion those substances with the highest melting points will tend to crystallize out first and in a state of comparative purity. 3. The liquid may contain two or more isomorphic compounds in which case the resulting mineral will contain each of these sub- stances usually in about the relative proportion in which they were present. Isomorphic compounds are generally salts of the same acids with the metallic elements different. Composition and Formula. It will thus be seen that many factors besides the results of analy- sis must be taken into consideration in giving a formula to any mineral. When, however, the errors of calculation, arising from the impurities and from the replacing of certain elements by others of different atomic weight but isomorphous with them, are elimi- nated, it is generally possible to assign a typical formula to the species. The difficulty becomes greater when the polysilicates and some other complicated minerals are studied and in no case must the formula for the species be considered as absolutely invariable for the individual. The results of alteration through atmospheric agencies, infiltration of water, etc., tend at times to so alter the individual that its composition varies widely from the type while at times this alteration is carried on so regularly and so far that new species of quite definite composition are formed. In expressing the composition by formulas the ordinary chemical symbols are used. The letter R is used to represent a varying group of iso- morphic or equivalent elements, and it may have the valency of these elements designated by dots above and to the right of the letter. When two elements as (Fe.Mg) are placed in parenthesis CHEMICAL COMPOSITION AND REACTIONS. 189 with a period between it, indicates that the two replace each other in all proportions in the different individuals of the species. Types. The most prominent types found among minerals are as follows : 1. The Elements, as Au, Ag, Cu, Sb, C, S. These are fre- quently alloyed with other elements as copper with silver, sulphur with selenium, etc. 2. The Oxides and Hydroxides for which water, H^O, serves as a type, as cuprite, CujO, brucite, Mg(0H)2. It is not necessary that the hydrogen atom or atoms be replaced by a single element. This replacement may be by a group of elements as in diaspore, AIO(OH) or on the other hand the oxygen may be partially re- placed by sulphur as in kermesite, Sb^S^O. 3. The Sulphides, derivatives of HjS, and to a less extent their analogues the selenides, tellurides, arsenides and antimonides, as galenite, PbS, clausthalite, PbSe, hessite, AgjTe, niccolite, NiAs. The hydrogen may be replaced by more than one element as in chalcopyrite, CuFeSj, or the sulphur may be partially replaced by arsenic as in arsenopyrite, FeAsS, by antimony as in stephanite, Ag5SbS4 and also by selenium and by tellurium, but to a less extent and with smaller tendency to form distinct species. 4. The Chlorides, derivatives of HCl, and to a less extent their analogues the fluorides, bromides, and iodides as halite, NaCl, fluorite, CaFj, bromyrite, AgBr, iodyrite, Agl. More than one metal may replace the hydrogen as in the double fluoride cryolite, NajAlFj, and chlorides, bromides, iodides or fluorides may crystallize together as in embolite, Ag(Cl.Br). 5. Nitrates, derivatives of HNO3, as nitre, KNO3; soda nitre, NaNOj; isomorphic or basic modifications are rare. 6. Carbonates, derivatives of H2CO3, as calcite, CaCOj ; sider- ite, FeCOj, etc. Isomorphic combinations are common, as dolo- mite (Ca. Mg)C03. The carbonates of Zn, Fe, Co, Mn, Ca and Mg are isomorphous, and also the carbonates of Ca, Ba, Sr and Pb. Consequently, minerals containing various combinations of these carbonates are found. Many basic salts of carbonic acid also occur, as malachite, Cu2(OH)2C03; azurite, Cu2(OH)2(C03)2. Car- bonates are also frequently found containing water of crystalliza- tion as natron, Na2C03 -f" loHjO. In a few instances a carbonate and a halogen salt crystallize together as in phosgenite, Pb2Cl2C03. I90 DESCRIPTIVE MINERALOGY. 7. Sulphates, derivatives of HjSO^, as anhydrite, CaS04; barite, BaSO^, etc. Isomorphic combinations are more common than simple sulphates. Among these may be noted sulphates containing two or more metals, as glauberite, Na2Ca(SO^j)2 ; those containing a sulphate and chloride, as kainite, MgSO^.KCl + 3H2O. Basic sul- phates are also numerous as brochantite, Cu2(OH)2S04.2Cu(OH)2, and some individuals of any of the previous types crystallize with water of crystallization, as copiapite, Fe2(FeOH)2(S04)5 + iSHjO. 8. Chromates, derivatives of H2Cr04, as crocoite, PbCrO^, and derivatives of HCr02, as chromite, FeCrjO^. These are the two important mineral chromates. Two or three rare basic compounds are also known. 9. MoLYBDATES, derivatives of H2MoO^, as Wulfenite, PbMoO^, which is the only important natural molybdate. 10. TuNGSTATES, derivatives of HjWO^, as scheelite, CaWOi- Tungstates also are rare. One or two isomorphic combinations are known, as in Wolframite, (Fe.Mn)W04. 11. Borates, derivatives of HBO2, H3BO3 or of H2B4O7, as sassolite, H3BO3; borax, ^3^f).j + loHjO. Metaborates are rare. Ulexite, CaNaBjOg + 6H2O, may be considered as a mo- lecular combination of CaB^O^ + NaBOz, while colemanite, Ca2B5- Oii + SH2O, would consist of CaB^O^ + Ca(B02)2. Most natural borates contain water of crystallization, and a few basic combina- tions are found. 1 2. Aluminates, derivatives of HAIO2, as spinel, Mg(A102)2 ; chrysoberyl, GI(A102)2. The aluminates are isomorphous with the ferrates and metachromates, consequently the Al may be partially replaced by Fe or Cr, while, on the other hand, the common alu- minates are themselves isomorphous, and the Mg, Fe, Zn and Mn salts replace each other in their characteristic spinels to a limited extent. 1 3. Phosphates, derivatives of H3PO1, as vivianite, Fe3(P04)2 + 8H2O. By far the majority of mineral species of phosphates are either isomorphic modifications or basic salts, both with and without water of crystallization. Simple phosphates may crystal- lize together, as in triphylite, Li(Fe.Mn)P04. Phosphates may crystallize with chlorides and fluorides, as in apatite, Q,2.^\.Y)I^0 ^^. Basic salts may be simple, as in turquois, Al2(OH)3P04 -h H2O, or may contain several metals, as in lazulite, (Mg.Fe.Ca)Al2(OH)2- CHEMICAL COMPOSITION AND REACTIONS. 191 14. Arsenates, derivatives of H3ASO4, form compounds very similar to the phosphates in molecular structure, as scorodite, FeAsO^ + 2H2O, a hydrous ferric arsenate; mimetite, 3Pb3(As04)2 + PbClj, a combination of the isomorphic arsenate and chloride; olivenite, Cu3(OH)As04, a basic copper arsenate. 15. Vanadinates and Columbates, derivatives of H3VO4 and HCbOj. The chief vanadinates are vanadinite, 3Pb3(V04)2 + PbClj, a molecular combination of lead vanadinate and chloride, and descloizite (Pb.Zn) (Pb.0H)V04, a basic lead vanadinate contain- ing zinc. The most important natural columbate is the mineral columbite, Fe(Cb03)2. 16. Silicates. — By far the largest number of minerals known fall under this subdivision. Isomorphic combinations are the rule, and these combinations are at times so complicated that it is almost impossible to give even a typical formula to the species. Basic and acidic salts are common, but the silicates do not show as great tendency to crystallize with water of crystallization as is possessed by some of the other classes of compounds. Those which do contain water of crystallization are commonly considered in a class by themselves, on account of their many resemblances. The basic elements most commonly replacing each other are Ca, Mg, Fe, Zn and Mn; Na, Li and K, and Al, B, Cr and Fe. The silicon is itself sometimes partially replaced by Al, as in anorthite, or by Ti, as in titanite. Calculation of Formulas. In expressing the composition of a mineral by a formula we have only the atomic weights of its component elements and the results of analysis from which to calculate. Hence the formulas given do not of necessity express the structure of the molecule, but only the composition ratio. In fact, the symbols adopted are always the simplest which can express the propor- tions shown by analysis to exist between the atoms and which satisfy their valences. The true molecular formulas are proba- bly always some unknown multiple of these symbols. For the purposes of mineralogy, however, the composition formulas are sufficient. An example may make this point clearer. A very pure speci- men of beryl gave the following results on analysis : 192 DESCRIPTIVE MINERALOGY. Per cent, GIO, . 14.01 AI2O3 19.26 SiO„ 66.37 The sum of the atomic weights for each group is : GIO = 25. Al203= 102. SiO, = 60. The results of analysis represent the proportion in which the groups are present in the molecule. Consequently, the relation between the number of groups must be : Percentage Atomic Proportionate Composition. Weights. Number of Groups. 14.01 f 25 = .56 19.26 -;- 102 = .189 66.37 - f 60 = 1. 106 Now, as fractional atoms cannot exist, our problem is simply to find the smallest number of whole groups which stand to each other in this relation, and, as .56 : .189 : 1.106 = 3 : i : 6, very nearly, therefore, the composition is represented by 3GIO + AljOg 4" 6Si02, which may be better written GljAlgSijOig, or, as it at once becomes evident that the proportion between silicon and oxygen is that of a metasilicate, GljA^SiOj)^. It will now be found, on calculating the theoretical percentage composition of Gl3Al2(Si03)5, that it agrees within the limits of error with that found by analysis, and as the twelve affinities of the six SiOj radicals are satisfied by those of Gl and Al atoms, the formula probably represents the composition of the compound. The true molecular formula is, however, ^GljA^SiOa)^ wherein n represents some whole number. The calculation is not generally as simple as the above example might indicate. Usually, minerals contain elements which seem foreign to their true composition, and which are present either as impurities or which replace analogous elements of the true mole- cule. In fact, many beryls contain Cs, Hj, Naj, Ca, or Mg replac- ing Gl; and Fe or Cr replacing Al. Such replacing elements, if present only in small quantities, must be converted into their equiv- CHEMICAL COMPOSITION AND REACTIONS. 193 alents of Gl or Al before the calculation for formula is made. No representative formula can ever be assigned from an analysis of impure material unless the nature and extent of the impurities are known. Clues are often obtained as to the constitution of the molecule which are entirely foreign to the percentage composition, but which materially assist in the construction of the formula. Thus HjO, present as water of crystallization, is driven off" at comparatively low temperatures, while the hydrogen of hydroxides or of acid or basic salts is usually expelled as water only under a temperature approaching that of ignition. Orthosilicates are known to be much less stable than metasilicates, and frequently are found altered to metasilicates. This fact sometimes aids in determining the for- mula of a compound which otherwise might be referred to either class. For instance, analytical results have been obtained for both andalusite and cyanite, which are satisfied by the formula AlaSiOj. This represents more oxygen than is present in any of the silicic acids, and part of the oxygen is therefore undoubtedly in com- bination with the aluminium. Two rational formulas now become possible, one an orthosilicate Al(A10)Si04, the other a metasilicate (A10)2Si03. Andalusite is much more easily decomposable than cyanite, which is not so easily altered. The first symbol is there- fore assigned to andalusite and the second to cyanite. CHAPTER XX. THE IRON MINERALS. The minerals described are ; Metal — iron. Sulphides and arsenides — pyrrhotite, pyrite, marcasite, arsenopyrite, leuco- PYRITE. Oxides MAGNETITE, FRANKLINITE, HEMATITE, MENACCAN- ITE, TURGITE, GOETHITE, LIMONITE. Sulphates COPIAPITE, MELAN- TERiTE. Phosphates — vivianite, triphylite. Arsenates — scoRO- DiTE, pharmacosiderite. Carbonate — siderite. Chromate — CHROMiTE. Columbate — columbite. Tungstate — wolframite. Economic Importance. The iron minerals have important and varied uses, which may briefly be described under the following heads : I. — In natural state. II. — For extraction of metal (ores of iron). III. — For extraction of acid constituents. IV. — For extraction of included metals. I. — Uses in Natural State. In 1898 the production of ocher, umber and sienna and natural oxide paints was 41,950 short tons.* Limonite and hematite are the principal natural oxides ground for paint. II. — ^Minerals Used as Ores of Iron. In the United States the minerals smelted for iron are, in order of quantity used,t hematite, limonite, magnetite, and siderite. Goethite and turgite are commercially included with limonite under the name brown hematite, and more or less ilmenite is smelted with other ores. The residues from the roasting of pyrites are sometimes used as a source of iron, but not in this country. In 1899 the United States produced 25,341,000 J long tons of iron ore, about three-quarters of which came from the Lake Su- perior region of Wisconsin and Minnesota, and about one-sixth came from the Southern States. ^ Mineral Industry, 1899. f John Birkinbine, in Mineral Resources of United States, 1892, gives as amouhts mined for one year: Hematite, 11,646,619 tons; limonite and goethite, 2,485,101 tons; magnetite, 1,971,965 tons; siderite, 192,981 tons. \ Engineering and Mining Journal, 1900, p. 3. THE IRON MINERALS. 195 The greater portion of the 60,000,000 tons of iron ore produced in the world each year is converted into pig iron. That is, the ore is deprived of its oxygen by the action of incandescent carbon and the hot reducing gases resulting from its combustion, and becomes a Hquid mass of metallic iron, combined and mixed with a little carbon, silicon, phosphorus, sulphur and other impurities. The furnace used is a vertical shaft, everywhere circular in horizontal section, but usually widening from the top downwards to a certain level, and then again narrowing to the hearth. Hot air is forced into the furnace through nozzles called tuyeres, entering just above the hearth. The ore and fuel are analyzed and some flux is added, which, when combined with the ash of the fuel and the foreign ingredi- ents of the ore, forms a definite silicate of known fusibility, called the slag. The temperature of the furnace differs at different levels^ but is practically the same at all times at any one level. The ore, charged in at the top, in alternate layers with fuel and flux, passes through zones of different temperatures as it descends, and is reduced, carburized, fused, and flows into the hearth. The slag forms in a definite zone after the complete reduction of the iron, and falls also to the hearth, but, being lighter, floats on the melted, iron until drawn off! From time to time the metal is run out into sand moulds, forming the pigs or pig iron of which 13,649,453 * long tons were produced in the United States in 1899. This pig iron, by various processes, is converted into wrought iron, cast-iron and steel. The mineral franklinite, after treatment for zinc, and certain man- ganiferous hematites and siderites, are smelted, and yield spiegel- eisen, an alloy of iron and manganese, used as a source of carbon and manganese in the manufacture of steel. III. — Minerals Used for Extraction of Acid Constituents. (a) For Sulphur. — Pyrite, and, to a less extent, marcasite and pyrrhotite, are very extensively used in the manufacture of sul- phuric acid. In 1898, 363,000 tons were so used in the United States. The sulphides are burned in furnaces with grates, and the gases are converted into sulphuric acid. The residues, in addition to iron, frequently contain copper, nickel or gold, and these are usually extracted later. * Engineering and Mining Journal, 1900, p. 3. 196 DESCRTPIVE MINERALOGY. (b) For Arsenic. — The mineral arsenopyrite is the chief source of arsenic. (c) For Chromium. — Practically all the chromium compounds derive their chromium from the mineral chromite, very little of which is now mined in the United States. The most important compounds manufactured are potassium bichromate used in calico printing, oxidizing rubber, bleaching indigo and in manufacturing . the chrome paints and matches ; potassium chromate used in the manufacture of aniline colors, etc., and ferro-chromium, which added to steel produces the tough alloy known as chrome-steel. {d) For Tungsten. — Tungsten and the tungstates are extracted from wolframite and scheelite. The world's product is not more than 600 to 700 tons, and is chiefly employed in the manufacture of crude tungsten for tungsten steel and sodium tungstate for rendering fabrics non-inflammable. IV.— Included Metals. (a) Gold and Silver. — Both pyrite and arsenopyrite frequently carry gold and a little silver, which may be extracted either directly by stamping and amalgamation or by treatment of the roasted residues with chlorine or potassium cyanide solution. {b) Nickel. — Pyrrhotite frequently carries nickel, and in 1898 about 2,700 tons of nickel were extracted from the pyrrhotite of Sudbury, Ontario. IRON. Composition. — Fe with more or less Ni, Cr, Co, Mn. General Description. — Masses and imbedded particles of white to gray metal, resembling manufactured iron. Many meteorites are alloys of nickel and iron and usually when polished and etched by dilute acid exhibit lines or bands, due to a crys- talline arrangement of alloys of different proportion ol Fe to Ni, see Figs. 375, 376. Physical Characters. — Opaque. Lustre, metallic. Color, steel-gray to iron- • black. Streak, metallic gray. H.,4to5. Sp. gr., 7.3 to 7.8. Tough and malle- able. Fracture, hackly. Before Blowpipe, Etc.— Infusible. Soluble in acids. In borax or salt of phos- phorus, reacts only for iron. F'G- 375- Fig. 376. Sections of iron meteorites etched with acid. THE IRON MINERALS. 197 Remarks. — Occurs in large masses on Disco Island, Greenland, and sparingly in some basalts, pyrite nodules, etc., and locally reduced by heat from the carbonate. Also found in most meteorites either as chief constituent or Us a spongy matrix or in disseminated grains. PYRRHOTITE.— Magnetic Pyrites, Mundic. Composition. — FenSn + j. FcgS^ to FejiS^, with frequently small percentages of cobalt or nickel. General Description. — Usually a massive bronze metallic min- eral, which is attracted by the magnet and can be scratched with a knife. Sometimes occurs in tabular hexagonal crystals. Physical Characters. H., 3.5 to 4.5. Sp. gr., 4.5 to 4.6. Lustre, metallic. Opaque. Streak, grayish-black. Tenacity, brittle. Color, bronze-yellow to bronze-red, but subject to tarnish. Attracted by the magnet. Before Blowpipe, Etc. — Fuses readily on charcoal to a black magnetic mass, evolves fumes of sulphur dioxide, but does not take fire. In closed tube, yields a little sulphur. In open tube, gives fumes of sulphur dioxide. Soluble in hydrochloric acid, with evolution of hydrogen sulphide and residue of sulphur. Similar Species. — Pyrrhotite resembles pyrite, bornite and nic- colite at times, but differs in being attracted by the magnet and by its bronze color on fresh fracture. Remarks, — Pyrrhotite is found in gabbros and schists and occasionally in the older eruptive rocks, also frequently in meteorites. It alters to pyrite, limonite and siderite. Immense quantities are found at Strafford and Ely, Vermont ; Sudbury, Canada, and Lancaster Gap, Pennsylvania. The last two deposits are nickeliferous, and are mined for this metal. Smaller beds are common. Uses. — It is one of the chief ores of nickel, probably from in- cluded minerals; and to some extent is an ore of sulphur. PYRITE.— Iron Pyrites, Fool's Gold. Composition. — FeSj (Fe 46.7, S 53.3 per cent.), often contain- ing small amounts of Cu, As, Ni, Co, Au. General Description. — A brass- colored, metallic mineral, frequently in cubic or other isometric crystals or in crystalline masses, which may be any shape, as botryoidal, globular, stalac- titic, etc. Less frequently in non-crystalline masses. 198 DESCRIPTIVE MINERALOGY. Fig. 377. Fig. 378. Fig. 379. Fig. 380. Fig. 381. Fig. 382. Fig. 38J. Fig. 386. Crystallization. — Isometric, class of diploid, p. 20. Most com- mon forms are cube a, Fig. 377, and pyritohedron e, Fig. 378, a: 2a:a : 6 : ^c. Crossed twins, Fig. 394, occur and fivelings, as in Fig. 391 of marcasite. Fig. 392. Fig. 393. Fig. 394. Angles mm =111° 47', dd = 80" 10', ee = 146° 55'. Physical Characters. H. 5.5 to 6. Sp. Gr., 6 to 6.2. Lustre, metallic. Opaque. Streak, grayish-black. Tenacity, brittle. Color, silver white to steel gray. Cleavage, prismatic (i 1 1" 47). Before Blowpipe, Etc. — In closed tube yields a red sublimate, yellow when cold. On charcoal yields abundant white fumes and arsenical odor and coating and fuses to a magnetic globule. After short treatment the residue is soluble in hydrochloric acid with evolution of hydrogen sulphide and precipitation of the yellow sul- phide of arsenic. The residue may react for cobalt. Insoluble in hydrochloric acid. Soluble in nitric acid with separation of sulphur. Similar Species. — Massive varieties of the metallic cobalt min- erals and varieties of leucopyrite resemble arsenopyrite and are only safely distinguished by blowpipe tests. Smaltite when mas- sive can be distinguished from cobaltiferous arsenopyrite only by its slight reaction with hydrochloric acid after fusion. Remarks. — Arsenopyrite is found chiefly in crystalline rocks with other metallic sulphides and arsenides. Throughout the Rocky Mountains it is a common mineral and frequently auriferous. A large deposit at Deloro, Canada, is mined for both arsenic and gold. The arsenopyrite found in New England usually contains cobalt. Uses. — Arsenopyrite is the source of most of the arsenic of commerce, and occasionally contains enough gold or cobalt to pay for extraction. 202 DESCRIPTIVE MINERALOGY. LEUCOPYRITE.— LoUingite. Composition. — Fe3Asj to FeAs, sometimes with Co, Ni, Au or S. General Description. — Massive silver-white or gray metallic mineral some- times occurring in orthorhombic crystals, closely agreeing in angles with crystals of arsenopyrite. Physical Characters.— Opaque. Lustre, metallic. Color, silver-white or gray. Streak, grayish-black. H. = 5 to 5.5. Sp. gr., 7 to 7.4. Brittle. Cleavage, basal. Before Blowpipe, Etc. — Like arsenopyrite, except that sulphur reactions are less pronounced or do not appear at all. MAGNETITE.— Lodestone, Magnetic Iron Ore. Composition. — FcjO^ (Fe, 72.4 per cent.) often contains Ti, Mg. General Description. — A black mineral with black streak and metallic lustre, strongly attracted by the magnet and occurring in all conditions from loose sand to compact coarse or fine grained masses. Crystallization. — Isometric, usually octahedra. Fig. 395, or Fig. 395. Fig. 396. Fig. 397. loosely coherent masses of imperfect crystals, sometimes the do- decahedron d, Fig. 396, or a combination of these, Fig. 399, or Fig. 398. Fig. 399. Magnetite in Schist, Geikie. Port Henry, Kemp. more rarely with the angles modified by the tetragonal trisoctahe- dron tf = rt : 3a : 3«, Fig. 397. THE IRON MINERALS. 203 Twinning parallel to an octahedral face occurs, sometimes shown by striations upon the octahedral faces, as in Fig. 399. Physical Characters. H., 5.5 to 6.5. Sp. gr., 4.9 to 5.2. Lustre, metallic to submetallic. Opaque. Color and Streak, black. Tenacity, brittle. Strongly attracted by magnet and sometimes itself a magnet (lodestone). Breaks parallel to octahedron. Before Blowpipe, Etc. — Fusible with difficulty in the reduc- ing flame. Soluble in powder in hydrochloric but not in nitric acid. Similar Species. — No other black mineral is strongly attracted by the magnet. Remarks. — Magnetite occurs chiefly in crystalline metamorphic rocks and in erup- tive rocks partly derived from silicates containing iron. It is little altered by expo- sure but organic matter reduces it to ferrous oxide which by oxidation becomes hema- tite, Fe^Og. It makes up about 12 per cent, of the iron ore mined in America, being obtained especially from the States of Pennsylvania, New York, New Jersey and Michigan. Smaller amounts are obtained elsewhere and it is present in many localities. In this country, lodestones are obtained mainly from Magnet Cove, Ark. Whole mountains are made up of this mineral in Sweden and it is practically the only iron-ore mined in that country. Uses — It is an important iron ore highly valued for its purity. FRANKLINITE. Composition. — (Fe.Mn.Zn) (Fe.Mn)204. fig. 400. General Description. — Black mineral re- sembling magnetite. Occurs in compact masses, rounded grains and octahedral crys- tals. Only slightly magnetic and generally with brown streak. The red zincite and yel- low to green willemite are frequent associ- ates. The crystals are modified octahedrons rarely sharp cut as in magnetite. Physical Characters. H.,6to6.5. Sp. Gr., 5 to 5.2. Lustre, metallic or dull. Opaque. Streak, brown to black. Tenacity, brittle. Color, black. Slightly magnetic at times. Breaks parallel to octahedron. 204 DESCRIPTIVE MINERALOGY. Before Blowpipe, Etc. — Infusible. On charcoal with soda gives white coat of zinc oxide. In beads gives manganese reaction. Slowly soluble in hydrochloric acid with evolution of some chlorine. Similar Species. — Distinguished from magnetite and chromite by bead tests and associates. Remarks. — The only noteworthy locality is that in the vicinity of Franklin Fur- race, New Jersey. Here, however, the deposit is large and has been extensively developed. Uses. — The zinc is recovered as zinc white and the residue is smelted for spiegeleisen an alloy of iron and manganese used in steel manufacture. Franklinite has also been ground for a dark paint. HEMATITE.— Specular Iron, Red Iron Ore. Composition. — FcjO.,, (Fe 70 per cent.), often with SiO,, MgO, etc., as impurities. General Description. — Occurs in masses varying from bril- liant black metallic to blackish red and brick red with little lustre. The black is frequently crystallized, usually in thin tabular crys- tals set on edge in parallel position, less frequently in larger highly modified forms-and finally in scale-like to micaceous masses. The red varieties vary from compact columnar, radiated and kidney- shaped masses to loose earthy red .material. In all varieties the streak is red. Crystallization. — Hexagonal, scalenohedral class p. 39. Axis c= 1.36557. The most common forms on the Elba crystals are the unit rhombohedron p and the scalenohedron n ^ ^ a : /\a : a : 2c . The rhombohedron g = a: as a : a : ^ c also occurs. Thin plate -like Fig. 401. Fig. 402. Fig. 403, crystals are the rule at other localities. Sometimes grouped in rosettes, as in the " Eisenrosen," Fig. 404. THE IRON MINERALS. 205 Angles. — pp = 86° ; nn = 128° i' ; <:/]= 122'' 23' ; gg-. 142° 58'; cn= 118° 47'. Fig. 404. Fig. 405. Eisenrosen, Fibia Switz. Radiated reniform, Geiki. Physical Characters. H., 5.5 to 6.5. Sp. gr., 4.9 to 5.3. Lustre, metallic to dull. Opaque. Streak, brownish red to cherry red. Tenacity, brittle un- CoLOR, iron black, blackish red to cherry red. less micaceous. Sometimes slightly magnetic. Before Blowpipe, Etc. — Infusible. Becomes magnetic in re- ducing flame. Soluble in hot hydrochloric acid. In borax reacts for iron. Varieties. Specular Iron. — Brilliant micaceous or in crystals. Black in color. Red Hematite. — Submetallic to dull, massive, blackish red to brownish red in color. Red Ochre. — Earthy impure hematite usually with clay. Often pulverulent. Clay Ironstone. — Hard compact red material mixed with much clay or sand. Martite. — Octahedral crystals, probably pseudomorphs. Similar Species. — Resembles at times the other iron-ores and massive cuprite. It is distinguished by its streak and strong mag- netism after heating in reducing flame. Remarks. — Usually in metamorphic rocks, probably formed from bog iron-ore by pressure and heat. Also found in igneous rocks. Changes by action of atmosphere, water, organic matter, etc., into limonite, siderite and magnetite. About 72 per cer.i. of the iron-ore mined in the United States is hematite. By far the larger part 'is obtained from the Marquette and Gogebic ranges of Michigan and from the Mesabi raiige in Minnesota. Smaller but by no means inconsideral^le amounts are mined in New York, Alabama, Missouri and other states. 2o6 DESCRIPTIVE MINERALOGY. Uses. — In this country it supplies over two-thirds of all the iron- ore mined, and ranks with magnetite in purity. The earthy varieties are used for a cheap paint, and some massive varieties are ground for paint or polishing material. ILMENITE.— Menaccanite, Titanic Iron-Ore. Composition. — (Fe.Ti)203, sometimes small amounts of Mg or Mn. General Description. — An iron-black mineral, usually massive or in thin plates or imbedded grains or as sand. Also, in crystals closely like those of hematite in angle. Crystallization. — Hexagonal. Class of third order rhombohe- dron p. 46. Axis ^= 1.385. Usually thick plates showing basal pinacoid c, unit prism in and unit rhombohedron /, Fig. 407, or without the prism. Fig. 406. Angles />/ = 8 5 " 31' ; f/= 122° 2'. Fig. 406. Fig. 407. Physical Characters.— H., 5 to 6. Sp. gr., 4.5 to 5. Lustre, submetallic. Opaque. Streak, black to brownish-red. Tenacity, brittle. Color, iron-black, Slightly magnetic. Before Blowpipe, Etc. — Infusible in oxidizing flame ; slightly fusible in reducing flame. In salt of phosphorus gives a red bead which, on treatment in reducing flame becomes violet, slowly soluble in hydrochloric acid and the solution boiled with tin is violet and on evaporation becomes rose-red. Similar SPECiES.^Differs from magnetite and hematite in the titanium reactions. Remarks. — Menaccanite occurs in crystalline rocks, often with magnetite. It is sometimes altered to limonite and to titanite. Immense beds occur at Bay St. Paul, Quebec, and other points in Canada. Found also in the county of Orange, N. Y., in Massachusetts, Connecticut, and elsewhere. A Norwegian locality Kragero, is, for its large crystals, perhaps the most celebrated. THE IRON MINERALS. 207 Uses. — It is used as a constituent of the lining of puddling fur- naces. Its freedom from impurities, such as phosphorus, would make it a very desirable iron-ore if it were not for the relatively large amount of fuel needed to reduce it. GOETHITE. Composition. — FeO(OH). Fe, 62.9 per cent. General Description. — A yellow, red or brown mineral, occurring in small, dis- tinct, prismatic crystals (orthorhombic), often flattened like scales, or needle-like, or grouped in parallel position. These shade into feather-like and velvety crusts. Oc- curs also massive like yellow ochre. Physical Characters. — Opaque to translucent. Lustre, adamantine to dull. Color, yellow, reddish, dark-brown and nearly black. Streak, yellow or brownish-yel- low. H., 5 to 5.5. Sp. gr., 4 to 4.4. Before Blowpipe, Etc. — Fuses in thin splinters to a black magnetic slag. In closed tube yields water. Frequently reacts for manganese. Soluble in hydrochloric acid- Uses. — Goethite is an ore of iron, but is commercially classed with limonite under the name of brown hematite. Large deposits are reported in Minnesota. TURGITE.— Hydrohematite. Composition. — Fe^Oj (OH)^, Fe = 66.2 per cent. General Description. — Nearly black botryoidal masses and crusts resembling limonite but with a red streak and often with a fibrous and satin-like appearance on fracture. Also bright red earthy masses. Usually associated with limonite or hematite. Physical Characters. — Opaque. Lustre, submetallic to dull. Color, dark reddish- black in compact form to bright red in ocherous variety. Streak, brownish red. H., 5.5-6. Sp. Gr., 4.29-4.68. Before Blowpipe, Etc. — Decrepitates violently, turns black and becomes magnetic. Yields water in closed tube with violent decrepitation. Similar Species. — Is distinguished from limonite and hematite Fig. 408. by its violent decrepitation when heated. Remarks. — Like goethite it is frequently mistaken for and classed with Umonite. It occurs with limonite at Salisbury, Conn., and in various localities in Prussia and Siberia. It is considered an inter- mediate stage in the formation of hematite from limonite. Uses. — It is an ore of iron but commercially is classed as limonite. LIMONITE.— Bog-Ore, Brown Hematite. Composition. — Fe2(OH)uFe203, (Fe, 59.8 per cent.). Frequently quite impure, from sand, clay, manganese, phosphorus, etc. General Description. — Never crystallized, but grading from the loose, porous bog-ore and earthy ochre of brown to yellow color ; to compact varie- ties, often with black varnish-like surface, and fibrous radiated structure. Frequently stalactitic. Fig. 408. Hungary. 2o8 DESCRIPTIVE MINERALOGY. Limonite is recognized principally by its yellowish-brown streak and absence of crystallization. It is frequently found pseudomorph- ous, the original iron-bearing mineral having "changed" to limonite. Physical Characters. H., 5 to 5.5. Sp. gr., 3.6 to 4. Lustre, varnish-like, silky, dull. Opaque. Streak, yellowish-brown. Tenacity," brittle, earthy. Color, brown, nearly black, yellow like iron rust. Before Blowpipe, Etc. — In closed tube yields water, and be- comes red. Fuses in thin splinters to a dark magnetic slag. Usu- ally reacts for silica and manganese. Soluble in hydrochloric acid, and may leave a gelatinous residue. Varieties. Bog-Iron, loosely aggregated ore from marshy ground, often intermixed with and replacing leaves, twigs, etc. Yellow ochre, umber, etc., earthy material, intermixed with clay. Brown clay ironstone, compact, often nodular masses, impure from clay. Similar Species. — Distinguished from other iron-ores, except goethite, by its streak, and from the latter by lack of crystalliza- tion. Remarks. — One usual result of the decomposition of any iron-bearing mineral is limonite. The decomposition by water, carbon dioxide and organic acids, produces soluble iron salts, which are carried to some valley by the streams, and by oxidation the relatively insoluble limonite forms as a scum on the water and then sinks to the bottom as bog-ore. In time, by pressure, heat, etc., these deposits are compacted. Limonite constitutes about 15 per cent, of the iron-ore mined in the United Stales. The largest deposits which are regularly mined exist in the States of Virginia, Alabama, Pennsylvania, Michigan, Tennessee, and Georgia. Uses. — It is the most abundant ore of iron, but is relatively impure and low in iron. The earthy varieties are used as cheap paints, and after burning are darker in color, and are called burnt umber, burnt sienna, etc. COPIAPITE.— Misy. Composition.— Fe2(FeOH)2(SO,)5 + i8H,0, (Fep, 30.6, SO3 38.3, HjO 3 1. 1 per cent.) often with some AljOg or MgO. General Description. — Brownish-yellow to sulphur-yellow mineral, occurring granular massive, or in loosely compacted crystalline scales, rarely, as tabular monoclinic crystals. It has a disagreeable metallic taste. THE IRON MINERALS. 209 Physical Characters. H., 2.5. Sp. gr., 2.1. Lustre, pearly, feeble. Translucent. Streak, yellowish-white, Taste, metallic, nauseous. Color, brownish-yellow to sulphur-yellow. Before Blowpipe, Etc. — On charcoal, fuses and becomes mag- netic. Yields much water in closed tube, and some sulphuric acid. Soluble in water. Decomposed by boiling water. With soda gives sulphur reaction. Remarks. — Copiapite results from the oxidation of pyrite, marcasite and pyrrho- tite. It occurs with these minerals and with other sulphates. MELANTERITE.— Copperas. Composition.— FeSOj + 7H2O. (Fe^Oa 25.9, SO3 28.8, H^O 45.3 per cent.). General Description. — A pale green fibrous efflorescence on pyrite or marcasite, or stalactitic massive or pulverulent. It has a sweet astringent taste. Rarely in monoclinic crystals. On exposure it becomes dull yellowish white. Physical CHARACTERS.^Translucent. Lustre, vitreous or dull. Color, vitriol green to white. Streak, white. H., 2. Sp. gr., 1.8 to 1.9. Taste, astringent, sweet- ish. Before Blowpipe, Etc. — On charcoal fuses becoming successively brown, red, and finally black and magnetic. With soda, yields sulphur test. In closed tube yields water and both sulphuric and sulphurous acids. Soluble easily in water, the solution becom- ing black (ink) on addition of nut galls. VIVIANITE.— Blue Iron Earth. Composition.— Fe3(P04)2 + 8H2O. (FeO 43.0, P^Oj 28.3, Hp 28.7 per cent.). General Description. — Usually found as a blue to bluish green earthy mineral, often replacing organic material as in bones, shells, horn, tree roots, etc. Also found as glassy crystals (monoclinic), colorless before exposure, but gradually becoming blue. Physical Characters. — Transparent to opaque. Lustre, vitreous to dull. Color and streak, colorless before exposure, but usually blue to greenish. H=I.5 to 2. Sp. gr., = 2.58 to 2.69. Brittle. Before Blowpipe, Etc. — Fuses easily to a black magnetic mass and colors flame pale bluish-green, especially after moistening with concentrated sulphuric acid. In closed tube yields water. Soluble in hydrochloric acid. The dried powder is brown. TRIPHYLITE. Composition. — Li(Fe.Mn)P04. General Description. — Usually a translucent bluish-gray, massive mineral with somewhat resinous lustre, and two easy cleavages at 90° to each other. Also in nearly black orthorhombic crystals. Physical Characters, — Translucent to opaque. Lustre, resinous. Color, blu- ish-gray, green, brown. Streak, white. H., 4.5 to 5. Sp. gr., 3.4 to 3.56. Brittle. Cleavages at 90°. 210 DESCRIPTIVE MINERALOGY. Before Blowpipe, Etc. — Fuses easily, coloring the flame carmine red and after moistening witli concentrated sulphuric acid may also show a pale blue tint. Reacts in beads for iron and manganese. Soluble in hydrochloric acid. SCORODITE. Composition.— FeAs04 + 2HjO. (FeO 34.6 ASJO549.8. HjO 15.6 per cent.). General Description. — Usually found as small pointed orthorhombic crystals, or druses of crystals of either a pale bluish-green or dark brown color. More rarely occurs earthy. Physical Characters. — Translucent. Lustre, vitreous. Color, pale green to dark brown. Streak, white. H., 3.5 to 4. Sp.gr., 3.1 to 3.3. Brittle. Before Blowpipe, Etc. — On charcoal fuses easily, with a pale blue flame and odor like garlic, to a brown or black magnetic mass. Easily soluble in hydrochloric acid but insoluble in nitric acid. PHARMACOSIDERITE.— Cube Ore. Fig. 409. Composition.— Fe(FeOH)3 (AsOJ, + 6HjO. (FCjOj 40.0, AsjOj 43.1 HjO 16.9 per cent.). General Description. — Groups of small translucent cubes or modified tetrahedrons of green or yellowish-brown color. More rarely granular. Physical Characters. — Translucent. Lustre, adaman- tine. Color, emerald or olive-green, or yellowish-brown. Streak, paler than color. H., 2.5. Sp. gr., 2.9 to 3. Slightly sectile. Before Blowpipe, Etc. — As for scorodite. SIDERITE.— Spathic Ore. Composition. — FeCOj (FeO 62.x, COj 37.9 per cent.) usually Fig. 410. with some Ca, Mg or Mn. General Description. — Occurs gran- ular massive of a gray or brown color and also in masses with rhombohedral cleav- age and rhombohedral crystals. At times it is quite black from included carbona- ceous matter. Crystallization. — Hexagonal. Sca- lenohedral class p. 39. Axis c = 0.8184. Usually rhombohedrons of 107°, often with curved (composite) faces like those of dolomite. Optically, — with strong double re- fraction. THE IRON MINERALS. 211 Physical Characters. H., 3.5 to 4. Sp. gr., 3.83 to 3.88. Lustre, vitreous to pearly. Opaque to translucent. Streak, white or pale yellow. Tenacity, brittle. Color, gray, yellow, brown or black. Cleavage, rhombohedral R/\R= 107". Before Blowpipe, Etc. — Decrepitates, become black and mag- netic and fuses with difficulty. Soluble in warm acids with effer- vescence. Slowly soluble in cold acids. May react for man- ganese. Similar Species. — It is heavier than dolomite and becomes mag- netic on heating. Some stony varieties resemble varieties of sphal- erite. Remarks. — Siderite occurs as beds in gneiss, mica and clay-slate, etc., and as stony impure material in the coal formation. Frequently with metallic ores. It is probably chiefly formed by the action of decaying vegetation on limonite. An impure siderite forms the chief ore in Cornwall and other English mines. It is found at Cats- kill, N. Y., and in the coal regions of Pennsylvania, Ohio, Virginia, and Tennessee, in varying quantities, but forms only a little over one per cent, of American iron ore. Uses. — It is used as an ore of iron and when high in manganese it is used for the manufacture of spiegeleisen. CHROMITE.— Chromic Iron. Composition. — FeCrjO^, (FeO 32, Cr^Oj 68 per cent), some- times with AI2O3 or MgO as replacing elements. General Descriptiom. — Usually a massive black mineral resem- bling magnetite. Occurs either granular or compact or as dissem- inated grains. Rarely in small octahedral crystals. Frequently with more or less serpentine, mechanically intermixed, giving rise to green and yellow spots and streaks. Physical Characters. H., 5.5. Sp. gr., 4.3 to 4.6. Lustre, sub-metallic to metaUic. Opaque. Streak, dark-brown. Tenacity, brittle. Color, black. May be slightly magnetic. Before Blowpipe, Etc.— Infusible, sometimes slightly fused by reducing flame, and iken becomes magnetic. In salt of phos- phorus, in oxidizing flame, gives yellow color hot, but on cooling becomes a fine emerald-green. With soda and nitre on platinum fuses to a mass, which is chrome-yellow when cold. Insoluble in acids. 212 DESCRIPTIVE MINERALOGY. Similar Species. — Chromite is distinguished from other black minerals by the salt of phosphorus reactions, and to a consider- able extent by the serpentine with which it occurs. Remarks. — Chromite occurs in veins and masses in serpentine and has been found in large isolated pockets in Southern Pennsylvania and around Baltimore, Md., but the richest ore has been exhausted, and most of the ore now used is brought from Turkey and from Nevif Caledonia. Extensive deposits are also found in Del Norte, San Luis Obispo, Shasta and Placer Counties, California, but of somewhat lower grade. Uses. — Chromite is the source of the various chromium com- pounds, such as potassium bichromate, the chrome colors, etc. It is also used in the manufacture of a hard chrome steel. COLUMBITE.— Tantalite. Composition. — Fe(Cb03)2, (FeO 17.3, Cb^Oa 82.7), but grading into tantalite. Fe (TaOj), without change of crystalline form. Mn is often present. General Description. — Black, often iridescent prismatic crystals, in veins of gran- ite. More rarely massive. Physical Characters.— Opaque. Lustre, bright sub-metallic. Color, black. Streak, dark-red to black. H., 6. Sp. Gr, 5.4 to 6.5. Brittle. Cleavage in two directions at right angles. Before Blowpipe, Etc — Infusible. Fused with potassium hydroxide and boiled with tin gives deep-blue solution. Insoluble in acids. WOLFRAMITE. •Composition. — (Fe.Mn) WO4. (About 76.5 per cent. WO3.) General Description. — Heavy dark-gray to black sub-metallic crystals, orthorhombic in appearance, and also in granular or columnar masses. Fig. 411. Crystallization. — Monoclinic. Axes a:b:'c = 0.830 : I : 0.868, /9 = 89° 22'. Usual combination shown in Fig. 411 of unit prism m, ortho pinacoid a, unit clinodome d and -f and — ortho domes ^ = ^ : 00 b-.y^c. Angles, mm= 100° 37 ; dd= 98° 6' ; ae 118° 6' ; ae = 1 17" 6'. . i/.... Zinnwald. Physical Characters, H., 5 to 5.5. Lustre, sub-metallic. Streak, dark-brown to black. Color, dark-gray to black. Sp. gr., 7.1 to 7.55. Opaque. Tenacity, brittle. Slightly magnetic. THE IRON MINERALS. 213 Before Blowpipe, Etc. — Fuses readily to a crystalline globule, which is magnetic. In salt of phosphorus yields a reddish -yellow glass, which in reducing flame becomes green, and if this bead is pulverized and dissolved with tin, in dilute hydrochloric acid, a blue solution results. Partially soluble in hydrochloric acid, the solution becoming blue on addition of tin. Similar Species. — Distinguished by its fusibility and specific gravity from similar iron and manganese minerals. Remarks. — Wolframite occurs in tin veins and deposits and witli other metallic minerals. It occurs altered to Scheelite and also pseudomorphous after scheelite. It Is common in the Cornwall and Zinnwald tin mines. It is also found at Flowe Moun- tain, N. C, Monroe and Trumbull, Ct., Black Hills, Dakota, Mine la Motte, Mo., and elsewhere. Uses. — It is used to make an alloy of tungsten with steel, espe- cially valued for permanent magnets, and as a source of tungsten salts, especially tungstic acid and sodium tungstate, which are used in dyeing, and as material to render cotton less imflammable. CHAPTER XXI. THE MANGANESE MINERALS. The minerals described are* Sulphide. — alabandite. Oxides. — BRAUNITE, HAUSMANNITE, PYROLUSITE, MANGANITE, PSILOMELANE, WAD. Phosphates. — triplite. Carbonate. — rhodochrosite. The principal economic use of manganese minerals is in the pro- duction of the alloys with iron, spiegeleisen and ferromangaHese , used in the manufacture of steel. About nine-tenths of all the manganese ore mined is used for this purpose. The method of smelting is very like that used in the manufacture of pig-iron. Minor uses are in the manufacture of chlorine, oxygen, disinfect- ants, driers for varnishes ; as a decolorizer of glass and to color glass, pottery and bricks ; in dyeing calico, making paints, etc. In the West, especially Colorado and Arizona, manganese ores often carry silver, and several thousand tons are smelted each year with other silver-bearing minerals, the manganese acting as a flux. The manganese minerals important as ores are the oxides pyrolusite, psilomelane (including wad), braunite and manganite. In 1898 the United States produced 217,782 long tons of man- ganese ore.f ALABANDITE.— Manganblende. Composition. — MnS, (Mn 63.1, S 36.9 per cent.). General Description. — A dark iron-black metallic mineral with an olive green powder or streak. Usually massive, with easy cubic cleavage and occasionally in cubic or other isometric crystals. Also massive granular. Physical Characters. — Opaque. Lustre, metallic. Color, deep black with brown tarnish. Streak, olive green. H., 3.5 to 4. Sp. gr., 3.95 104.04. Brittle. *The common silicate, rhodonite, which has no economic importance, is described under the silicates. f Mineral Industry, 1899, p. 499. THE MANGANESE MINERALS. !I5 Before Blowpipe, Etc.— Turns brown, evolves sulphur dioxide and fuses. Gives sulphur reactions with soda. Soluble in dilute hydrochloric acid with rapid evolution of hydrogen sulphide. Similar Species — It is distinguished from all similar species by its streak. Remarks.— The other manganese minerals are derived in part from the alteration of this species. It occurs with other metallic sulphides. BRAUNITE. Composition. — MriaOj, but usually containing MnSiOj. General Description. — Brownish black granular masses and occasional minute tetragonal pyramids almost isometric, i = 0.985. Physical Characters. H., 6 to 6.5. Lustre, submetallic. Streak, brownish black. Color, brownish black to steel gray. Sp. gr., 4.7s to 4.82, Opaque. Tenacity, brittle. Before Blowpipe, Etc. — Infusible. With borax an amethys- tine bead. Soluble in hydrochloric acid, evolving chlorine and generally leaving gelatinous silica. Similar Species. — Resembles hausmannite, but has a darker streak and is harder. Uses. — It occurs in large quantities in India and smaller amounts elsewhere, and is an ore of manganese. Fig. 412. Fig. 413. Fig. 414. Braunite//= 102° 15' Hausmannite, pji = 105° 26' hausmannite. Composition. — MnjO^. (MujOj 69.0, MnO 31.0 per cent.). General Description. — Black granular strongly coherent masses occasionally in simple and twinned tetragonal pyramids which are more acute than those of braunite, c=i.l74. Physical Characters.— Opaque. Lustre, submetallic. Color, brownish black. Streak, chestnut brown. H., 5 to 5.5. Sp. gr., 4.72 to 4.85. Strongly coherent. Before Blowpipe, Etc. — Infusible. C-jlors borax bead amethystine. Soluble in hydrochloric acid with evolution of chlorine. Similar Species. — Differs from braunite in hardness, streak and absence of silica. 2l6 DESCRIPTIVE MINERALOGY. PYROLUSITE.— Black Oxide of Manganese. Composition. — MnOj, (Mn 63.2 per cent). Fig. 415. Florence, Italy. General Description. — ^A soft black mineral of metallic lustre. Frequently composed of fibres or columns often ra- diated, but also found fine grained, massive, stalactitic, and as velvety crusts. It is also the common dendrites. Fig. 415. Usually soils the fingers. Frequently in alter- nate layers with psilomelane. Physical Characters. H., i to 2.5. Lustre, metallic or dull. Streak, black. Color, black to steel gray. Sp. gr., 4-7 to 4-86. Opaque. Tenacity, rather brittle. Before Blowpipe, Etc. — Infusible, becomes brown. Usually yields oxygen and a little water in closed tube. Colors borax bead amethystine. Soluble in hydrochloric acid with evolution of chlorine. Similar Species. — Distinguished by its softness and black streak from other manganese minerals. Remarks. — Pyrolusite results from the dehydration of manganite and the altera- tion of alabandite and rhodochrosite. It is usually with psilomelane, hematite, limon- ite or manganite. By far the larger part of all that is mined in this country is obtained from Crimera, Va., Cartersville, Ga., and Batesville, Ark. Other deposits exist in California, Ver- mont and North Carolina. Large amounts are annually imported from Cuba. The purest material for use in glass making is obtained near Sussex, N. B., and from the Tenny Cape district. Nova Scotia. Uses. — Pyrolusite is used in the manufacture of chlorine and oxygen, and in the preparation of spiegeleisen. Also in coloring and decolorizing glass and as an oxidizing agent in varnishes, linseed oil, etc. MANGANITE. Composition.— MnO(OH), (Mn 62.4,0 27.3, H^O 10.3 percent.). General Description. — Occurs in long and short prismatic THE MANGANESE MINERALS. 217 (orthorhombic) crystals often grouped in bundles with fluted or rounded cross-section and undulating terminal surface, rarely mass- ive, granular or stalactitic. Physical Characters, H., 4. Sp. gr., 4.2 to 4.4. Lustre, submetallic. Opaque. Streak, reddish brown to black. Tenacity, brittle. Color, steel gray to iron black. Before Blowpipe, Etc. — Like pyrolusite, but yields decidedtest for water and very little oxygen. Remarks. — Frequently formed by deposition from water. By alteration it forms other manganese minerals such as pyrolusite. PSILOMELANE.— Black Hematite. Composition.— Perhaps Mn02+ (H2O, K^O or BaO) or H^MnOj, with replacement by Ba or K. General Description. — A smooth black massive mineral com- monly botryoidal, stalactitic or in layers with pyrolusite. Never crystallized. Physical Characters. H., 5 to 6. Sp. gr., 3.7 to 4.7. Lustre, submetallic or dull. Opaque. Streak, brownish black. Tenacity, brittle. Color, iron black to dark gray. Before Blowpipe, Etc. — Infusible.* In closed tube yields oxygen and usually water. Soluble in hydrochloric acid, with evolution of chlorine. A drop of sulphuric acid added to the solu- tion will usually produce a white precipitate of barium sulphate. Similar Species. — Distinguished from pyrolusite by its hard- ness, and from limonite by its streak. Remarks. — Its localities are the same as for pyrolusite, and the two minerals are usually mined together. Uses. — As for pyrolusite ; the products, however, are less pure. WAD. — Bog Manganese. Composition. — Mixture of manganese oxides, with often oxides of metals other than manganese such as cobalt, copper and lead. General Description. — Earthy to compact indefinite mixtures of different metal- lic oxides, in which those of manganese predominate. Dark brown or black in color; often soft and loose, but sometimes hard and compact. * May become magnetic from impurities. 21 8 DESCRIPTIVE MINERALOGY. Physical Characters.— Opaque. Lustre dull. Color brown to black. Streak brown. H., yi to 6. Sp. gr., 3 to 4.26. Often soils the fingers. Before Blowpipe, Etc.— As for psilomelane, but often with strong cobalt or copper reactions . Uses. — Wad is used as a paint and in the manufacture of chlorine. TRIPLITE. Composition. — (RF)RPOi. R chiefly manganese and iron. General Description. — A resinous, brown to nearly black mineral, usually massive and often showing cleavage in two directions at 90° to each other. Sometimes occurs as a stain on other minerals. Physical Characters. — Opaque or nearly so. Lustre resinous. Color brown to nearly black. Streak gray to brown. H., 4 to 5. Sp. gr., 3.44 to 3.8. Bef03;e Blowpipe, Etc.— Fuses very easily to a black magnetic mass. Yields a. bluish-green flame, which sulphuric acid makes plainer. Colors borax bead amethys- tine. When heated with sulphuric acid, evolves fluorine. Soluble in hydrochloric acid. RHODOCHROSITE. Composition.— MnCOg, (MnO 61.7, CO^ 38.3 per cent) with g partial replacement by Ca, Mg or Fe. General Description. — Occurs in rhom- bohedral crystals, but more frequently massive cleavable, or granular or compact. Less fre- quently botryoidal or incrusting. Crystallization. — Hexagonal. Scaleno- hedral class, p. 39. Axis 6- = . 8 1 84. Angles as in siderite. Usual form a rhombohedron of 107". Optically. — Physical Characters. H., 3.5 to 4.5. Sp. gr., 3.3 to 3.6. Lustre, vitreous to pearly. Transparent to opaque. Streak, white. Tenacity, brittle. Color, light pink, rose red, brownish red and brown. Cleavage, parallel to rhombohedron (angle 107°). Before Blowpipe, Etc. — Infusible, but decrepitates violently and becomes dark colored.* In borax yields amethystine bead. Soluble in warm hydrochloric acid, with effervescence, slowly sol- uble in the cold acid. Similar Species. — Distinguished from rhodonite by form, cleav- age, effervescence and infusibility. Remarks. — Principally found in ore-veins, especially with ores of manganese and silver. On exposure, sometimes loses color or becomes spotted by oxide. Found at Mine Hill, N. J. ; Butte, Montana; Austin, Nev. and elsewhere. It is not mined, however, in this country. The only producing locahties are Merionethshire, Wales, and Chevron, Belgium. * May become magnetic from impurities. CHAPTER XXII. NICKEL AND COBALT MINERALS. THE COBALT MINERALS. The cobalt mineral's described are : Sulphides and Arsenides, Lin- N^iTE, CoBALTiTE, Smaltite ; Arsenates, Erythrite. The metal cobalt has, as yet, no important use ; the oxide is used to impart a blue color to glass and pottery. The chief com- mercial compound is Smalt, a cobalt glass, the cobalt replacing the calcium of ordinary glass. This is ground and used as a fine blue pigment, which is unaltered by exposure. Cobalt blue and Rinmann's green are compounds of cobalt with alumina and zinc oxide respectively. The extraction of cobalt from a nickeliferous matte is an elabor- ate chemical operation involving solution in hydrochloric acid, pre- cipitation of manganese and iron as basic carbonates, and of other metals as sulphides, leaving a solution of chloride of nickel and co- balt. From these the cobalt is precipitated with great care, by means of calcium hypochlorite, as cobaltic hydroxide, after which the nickel is precipitated as hydroxide by lime-water. By using selected ores, mattes especially rich in cobalt may be obtained and for ordinary purposes the small nickel contents are neglected. LINNiEITE.— Cobalt Pyrites. Composition. — (Co.Ni)3S^, often with some Fe or Cu replacing. General Description. — A steel-gray metallic mineral, usually in granular or compact masses intermixed frequently with chal- copyrite ; also in small isometric crystals, usually the octahedron /, Fig. \\:j, or this with the cube a. Fig 418. Fig. 417. Fig. 418. * Cobalt is sometimes found in arsenopyrite. Asbolite is a black earthy oxide of cobalt and manganese. 220 DESCRIPTIVE MINERALOGY. Physical Characters. H., 5.5. Sp. gr., 4.8 to 5. Lustre, metallic. Opaque. Streak, nearly black. Tenacity, brittle. Color, steel-gray, with reddish-tarnish. Cleavage, cubic imperfect. Before Blowpipe, Etc. — On charcoal fuses to a magnetic glob- ule, and gives off fumes of sulphur dioxide. In borax bead gives a deep blue color, and with frequent replacement of borax the red bead of nickel may be obtained. Soluble in nitric acid to a red solution and with separation of sulphur. Remarks. — Occurs with other cobalt and nickel minerals and with chalcopyrite, pyrrhotite, bornite, at Mine La Motte, Mo., Lovelock's Station, Nev., and in a few other American localities. ' Uses. — Does not occur in large amounts, but is used as a source of both cobalt and nickel. COBALTITE.— Cobalt Glance. Composition. — CoAsS, (Co 35.5, As 45.2, S 19.3 per cent.) General Description. — A silver white to gray metallic min- eral resembling linnseite in massive state but in crystals differing in that the forms are the pyritohedron e, and cube a, and these com- bined. Fig. 421. Fig. 419. Fig. 420. Fig. 421. Physical Characters Lustre, metallic. Streak, black. Color, silver white to gray H., 5.5. Sp. gr. 6 to 6.1. Opaque. Tenacity, brittle. Cleavage, cubic. Before Blowpipe, Etc. — On charcoal fuses to a magnetic glob- ule and evolves white fumes with garlic odor. Unaltered in closed tube. Soluble in warm nitric acid to rose-red solution, with resi- due of sulphur and arsenous oxide. NICKEL AND COBALT MLYERALS. 221 Uses. — It is used in the manufacture of smalt and in porcelain painting. SMALTITE. Composition. — (Co.Ni) ASj, varying widely in proportion of cobalt and nickel, and usually containing some iron also. General Description. — A tin-white to steel-gray metallic min- eral resembling linnaeite and cobaltite. Usually occurs granular massive, but also in isometric crystals, especially modified cubes with curved faces. Physical Characters, H., 5.5 to 6. Sp. gr., 6.4 to 6.6. Lustre, metallic. Opaque. Streak, black. Tenacity, brittle. Color, tin-white to steel-gray. Cleavage, octahedral. Before Blowpipe, Etc. — On charcoal fuses, yields white fumes with garlic odor and leaves a magnetic residue, which, when oxi- dized in contact with frequently replaced borax, yields successively slags colored by iron, cobalt, nickel and possibly by copper. In closed tube yields arsenical mirror. Soluble in nitric acid to a red to green solution according to proportion of cobalt and nickel. Partially soluble in hydrochloric acid, especially so after fusion, but yields no voluminous precipitate of yellow arsenic sulphide, as does arsenopyrite when similarly treated. Similar Species. — Differs from linnaeite and cobaltite in cleav- age, specific gravity ana blowpipe reactions. Differs from most arsenopyrite and tetrahedrite in the cobalt blue slags which it yields. It can best be distinguished from cobaltiferous arseno- pyrite by the reaction in acids after fusion. Remarks. — By oxidation produces arsenates of cobalt (erythrite) and nickel (an- nabergite). Occurs in veins with other metallic minerals, especially ores of copper, silver, nickel and cobalt. Especially abundant in the nickel mines of Saxony. Found at Chatham, Ct., Franklin Furnace, N. J., and in California. Uses. — It is the chief ore of cobalt. ERYTHRITE. Composition. — Co3(As04)2.8HjO, (CoO 37.5, AS2O5 38.4, H^O 24.1 per cent.). General Description. — Groups of minute peach red or crimson crystals forming a drusy or velvety surface. Also in small globular forms or radiated or as an earthy incrustation of pink color. 222 DESCRIPTIVE MINERALOGY. Physical Characters. — Translucent. Lustre, adamantine or pearly. Color, crimson, peach red, pink and pearl gray. Streak, paler than color. H., 1.5 to 2.5. Sp. gr., 2.91 to 2.95. Flexible in laminae. Before Blowpipe, Etc. — On charcoal fuses easily, evolves white fumes with garlic odor, and leaves a magnetic residue, which imparts the characteristic blue to borax bead. Soluble in hydrochloric acid to a light red solution. THE NICKEL MINERALS. The nickel minerals described are : Sulphides, Millerite, Pentlandite, Gersdorffite ; Arsenides, Niccolite, Chloan- THiTE ; Arsenate, Annabergite ; Carbonate, Zaratite ; Silicate, Garnierite. Metallic nickel is extensively used in different alloys, and, in- deed, was first obtained as a residual alloy with copper, iron and arsenic, in the manufacture of smalt. This alloy was called Ger- man silver or nickel silver and largely used in plated silverware. Later, a large use for nickel was found in coins, the United States Mint alone using nearly one million pounds between 1857 and 1884. In this alloy copper is in large proportion, the present five cent piece being 25 per cent, nickel, 75 per cent, copper, and in other coins the percentage of copper being still greater. The most extensive application of nickel at present is in the manufac- ture of nickel steel for armor plates and other purposes. The uses of nickel steel are continually increasing as the metal has some excellent properties possessed by no other alloy. To a limited extent nickel is used in a nickel-copper alloy for casing rifle bullets. A sulphate of nickel and ammonium is also manufactured in large amounts for use in nickel plating. The nickel of commerce is nearly all obtained either from the garnierite of New Caledonia or from the deposit of nickel -bearing sulphides at Sudbury, Ontario. The garnierite is smelted in a low blast furnace, with coke and gypsum, and the matte of nickel, iron and sulphur thus produced is alternately roasted and fused with sand, in a reverberatory furnace, until nearly all the iron has been removed. The nickel sulphide, by oxidation, is converted into oxide. Nickel oxide is obtained from the pyrrhotite and chalcopyrite of Sudbury, Canada. The ore is first roasted, which removes much of the sulphur, and is then smelted, together with nickel- bearing slags of previous operations. A nickel matte carrying NICKEL AND COBALT MINERALS. 223 much copper and some iron is produced through which air is blown in a sihca lined Bessemer converter and most of the iron is carried into the slag. A matte, rich in nickel and copper, results. This may be directly roasted and reduced by carbon to produce nickel-copper alloys for the manufacture of German silver. In order to separate the nickel the concentrated matte is fused with sodium sulphate and coke, after which the melted sulphides are allowed to settle. Under these conditions the copper and iron sulphides form a very fluid mass with the soda, and, with some nickel, rise to the top while the lower portions of the mass are highly nickeliferous. The two layers are separated and each is retreated in much the same manner. The nickel sulphide result- ing is partially roasted and is fused with sand, by means of which most of the iron is removed as a silicate in the slag. The nickel sulphide remaining is by oxidation converted into the oxide. The oxide is sold directly to steel makers or may be reduced to metal by mixing with charcoal and heating, white hot, in a graphite crucible. The world's annual output of nickel is about 6000 short tons. Nickel is now successfully refined by electrolysis, but the de- tails of the process are jealously guarded. It is doubtful, however, if nickel can be separated from cobalt in this manner although most other impurities are removed. A method both for the extraction of nickel from its ore and for its separation from cobalt promises to supersede those now in use. The process is based on the discovery that when carbon monoxide is passed over heated nickel, volatile nickle carbonyl, Ni(CO)^, is formed. This is the only volatile nickel compound known, and as cobalt does not react in this way, the separation of nickel from cobalt is easily accomplished. The reconversion of the nickel carbonyl into nickel and carbon monoxide is a simple operation. MILLERITE.— Capillary Pyrites. Composition. — NiS, (Ni 64.4 per cent.). General Description. — A brass-colored mineral with metallic lustre, especially characterized by its occurrence in hair-like or needle crystals, often interwoven or in crusts made up of radiating needles visible on fracture. Hexagonal. 224 DESCRIPTIVE MINERALOGY. Physical Characters. H., 3 to 3.5. Sp. gr., 5.3 to 5.65. Lustre, metallic. Opaque. Streak, greenish-black. Tenacity, crystals elastic. Color, brass or bronze yellow. Before Blowpipe, Etc. — On charcoal spirts and fuses to a brittle magnetic globule, which will color borax red. Soluble in aqua regia to a green solution, from which "potassium hydroxide precipitates a green nickelous hydroxide which is again soluble in ammonia to a blue solution. Remarks.— Millerite has probably been formed in the same way as pyrite. It is probable that the nickel in pyrrhotite is there as millerite. Other associates are siderite, hematite and dolomite. In the United States it has been obtained chiefly from the Lancaster Gap mine, in Pennsylvania, and at Antwerp, N. Y. Uses. — It is a valued ore of nickel. PENTLANDITE. Composition. — (Fe.Ni)S. General Description. — Light bronze-yellow, granular masses of metallic lustre, usually with chalcopyrite or pyrrhotite. Physical Characters. — Opaque. Lustre, metallic. Color, bronze yellow. Streak, black. H., 3.5-4. Cleavage, octahedral. Sp. gr., 4.6-5. Brittle. Before Blowpipe, Etc. — Fuses readily to a magnetic globule which reacts for iron and nickel. Remarks. — Occurs at Sudbury, Ontario, where it is mined for nickel. GERSDORFFITE. Composition.— NiAsS (Ni 35.4, As 45.3, S 19.3 per cent.) Ni often replaced by Fe or Co. General Description. — Usually massive, fine grained light steel gray. Occasion- ally small isometric crystals like those of pyrite. Physical Characters. — ^Opaque. Lustre, metallic. Color, light-steel gray. Streak, black. Brittle. H., 5.5, Sp. gr., 5.8-6.2. Before Blowpipe, Etc. — Fuses easily with decrepitation to a metallic globule giving off white fumes of arsenic trioxide. Residue is magnetic, and gives sulphur reactiop. Borax bead may yield nickel reaction, but this is often masked by cobalt or iron. Remarks. — Various uncertain minerals or mixtures have been referred to gersdorfiite. It occurs incrusting decomposed galenite and sphalerite at Phcenixville, Pa. , and in Sweden, Harz, Styria, etc. NICCOLITE.— Copper Nickel. Composition. — NiAs, (Ni 43.9 per cent.). As is replaced to some extent by Sb or S, and Ni by Fe or Co. General Description. — A massive mineral of metallic lustre, characteristic pale copper red color and smooth impalpable struct- ure. Sometimes the copper-red kernel has a white metallic crust. Occasionally occurs in small indistinct hexagonal crystals. NICKEL AND COBALT MINERALS. 225 Physical Characters. H., 5 to 5.5. Sp. gr., 7.3 to 7.67. Lustre, metallic. Opaque. Streak, brownish-black. Tenacity, brittle. Color, pale copper red with dark tarnish. Before Blowpipe, Etc. — On charcoal fuses easily, giving off white fumes with garlic odor and leaving a magnetic residue, which will color borax bead red and sometimes blue, in which case the borax must be renewed until the cobalt is all removed. In open tube yields a white sublimate and a yellowish- green pul- verulent residue. Soluble in concentrated nitric acid to a green solution, which may be tested as under millerite. Similar Species. — Differs from copper in hardness, black streak and brittleness. Remarks. — Its most abundant American localities are at Lovelock's, Nevada, and Tilt Cove, Newfoundland. Also obtained at Chatham, Conn., and Thunder Bay, Lake Superior. Uses. — It is an important ore of nickel. CHLOANTHITE. Composition. — NiAsj.Ni 28. i per cent., Ni often replaced by Fe and Co. General Description. — Tin white to steel gray metallic mineral which resembles smaltite, and by replacement of nickel by cobalt gradually grades into that mineral. Physical Characters. — Like smaltite. Before Blowpipe, Etc. — Like smaltite except that a nickel reaction is imparted to borax by the pure mineral. ANNABERGITE.— Nickel Bloom. Composition. — Ni3(As04)j.8H20, (NiO 37.4 AS2O5 3S.5, H^O 24.1 per cent.). General Description.— Pale apple-green crusts, and occasionally very small hair-like crystals. Usually occurs on niccolite or smaltite. Physical Characters. — Dull. Color, apple-green. Streak, greenish-white. H., I. Before Blowpipe, Etc. — On charcoal, fuses easily to a magnetic button, and be- comes dull and yellow during fusion, evolving garlic odor. In closed tube, yields water and darkens. With borax, gives red bead. Soluble in nitric acid. Remarks. — Results from the oxidation of niccolite or smaltite in moist air. ZARATITE.— Emerald Nickel. Composition.— NiCOj 2Ni(OH)2.4H20, (NiO 59.6 COj u.y H^O, 2S.7 per cent.). General Description, — Occurs only as a, thin varnish-like coating upon nickel- bearing chromite or magnetite. Physical Characters. — Translucent. Lustre, vitreous. Color, emerald-green. Streak, pale-green. H., 3 to 3.25. Sp. gr., 2,57 to 2.69. Brittle. Before Blowpipe, Etc. — Infusible. Colors borax bead red. In closed tube, yields water. Solul)le in warm dilute hydrochloric acid, with effervescence, to a green solution. 226 DESCRIPTIVE MINERALOGY. GARNIERITE.— Noumeite. Composition.— H,(Ni.Mg)SiO, + Hpor2(Ni.Mg)5SiA3-3H20. General Description. — Loosely compacted masses of brilliant dark-green to pale-green mineral, somewhat unctuous. Structure often small mamarelonated, with dark-green, varnish-like surfaces, enclosing dull green to yellowish ochreous material. Easily broken and earthy. Physical Characters. H., 2 to 3. Sp. gr., 2.27 to 2.8. Lustre, varnish-like, to dull. Opaque. Streak, light green to white. Tenacity, friable. Color, deep green to pale greenish-white. Unctuous, adheres to the tongue. Before Blowpipe, Etc. — Infusible, decrepitates. In closed tube yields water. Colors borax bead red. Partially soluble in hydro- chloric and nitric acids. Similar Species. — Differs from malachite and chrysocoUa in structure and unctuous feeling. Differs from serpentine in deep color and nickel reaction. Remarks. — Occurs in New Caledonia in veins in serpentine, with chromite and talc. Possibly derived from a nickel-bearing chrysolite. Deposits are also known at Riddles, Oregon and Webster, N. C. Uses. — It is now the chief source of nickel. CHAPTER XXIII. ZINC AND CADMIUM MINERALS. THE ZINC MINERALS. The zinc minerals described are : Sulphide — sphalerite. Oxide — ziNCiTE. Sulphate — goslarite. Carbonates — smithsonite, hy- DROziNciTE. Silicates — willemite, calamine. The important ores of zinc are sphalerite, smithsonite, and cal- amine ; and, in New Jersey, willemite and zincite occur in quan- tity sufificient to be considered ores. A large amount of zinc oxide is also made from franklinite which is described under the iron minerals. In this country, Missouri, Kansas, Indiana and Illinois yield most of the zinc ore, although other important regions are Penn- sylvania, New Jersey, and Virginia. The western ore contains lead ore, from which it is separated by concentration. In all, in 1899, this country produced 135,796 tons of metallic zinc and 31,663 tons of zinc oxide were manufactured.* The principal uses of metallic zinc are in galvanizing iron wire or sheets and in manufacturing brass. A smaller amount is made into sheet zinc and zinc dust. Metallic zinc is obtained by distillation of its roasted ores with carbon. The sulphide and carbonate, by roasting, are converted into oxide, and the silicates are calcined to remove moisture. The impure oxides, or the silicate, are mixed with fine coal and charged in tubes or vessels of clay, closed at one end and connected at the other end with a condenser. These are submitted to a gradually increasing temperature, by which the ore is reduced to metallic zinc, and, being volatile, distills, and is condensed. Apparently successful processes are now in use for the direct deposition of zinc from its ores by electrolysis. Zinc oxide, ground in oil, constitutes the paint zinc white. The oxide may be made from the metal by heating it to a temperature * Engineering and Mining Journal, 1900, p. 2. 228 DESCRIPTIVE MINERALOGY. at which the zinc takes fire and drawing the fumes into suitable condensers; or, as in this country, it may be made directly from the ore. SPHALERITE.— Blende, Black Jack. Composition. — ZnS, (Zn, 67 per cent). Often contains Cd, Mn, Fe. General Description. — A mineral of resinous lustre shading in color from yellow through brown to nearly black and more or less translucent. It occurs most frequently cleavable massive but also in crystals and in compact fine-grained masses or alternate concentric layers with galenite. Fig. 422. Fig. 423. Fig. 424. Crystallization. — Isometric. Hextetrahedral class p. 1 8. Usu- ally the dodecahedron d with the tetrahedron / and a modifying tristetrahedron =^ a : 3a : T,a, Fig. 424, or n = a: 2a: 2a, Fig. 423. More rarely the -|- and — tetrahedron, Fig. 422. Index of refraction for yellow light, 2.3692. Physical Characters. H., 3.5 to 4. Sp, gr., 3.9 to 4.1. Lustre, resinous. Transparent to translucent. Streak, white to pale brown. Tenacity, brittle. Color, yellow, brown, black ; rarely red, green or white. Cleavage, parallel to rhombic dodecahedron (angles 120° and 90°). Before Blowpipe, Etc.— On charcoal fuses with difficulty, but readily yields a sublimate, sometimes brown at first from cadmium and later yellow while hot, white when cold and becoming bright green if moistened and ignited with cobalt solution. With soda gives a sulphur reaction. Soluble in hydrochloric acid with effer- vescence of hydrogen sulphide. Similar Species. — Smaller crystals sometimes slightly resemble garnet or cassiterite, but are not so hard. Remarks. — Sphalerite has probably been formed by precipitation from water by H,S or with the aid of decaying organic matter. By oxidation it changes to sulphate which in turn may be decomposed by carbonates and silicates forming carbonates and ZINC AND CADMIUM MINERALS. 229 silicates of zinc. Sphalerite is a common associate of lead and silver ores and is det- rimental, as it makes their treatment more difficult. It also occurs with other sulphides and with other zinc ores. It is mined in southwest Missouri, at Friedensville, Pa., in the southwestern part of Wisconsin, at Pulaski, Va., and at other places. In small quantities it is of very common occurrence. Uses. — It is an important ore of zinc and also is the source of most of the cadmium of commerce. ZINCITE.— Red Zinc Ore. Composition. — ZnO, (Zn 80.3 per cent.) with usually some Mn or Fe. General Description. — A deep red to brick-red adamantine mineral occurring in lamellar or granular masses, either in calcite or interspersed with grains and crystals of black franklinite and yellow to green willemite. A few hexagonal pyramids have been found. Physical Characters. H., 4 to 4.5. Sp. gr., 5.4 to 5.7. Lustre, sub-adamantine. Translucent. Streak, orange yellow. Tenacity, brittle. Color, deep red to orange red. Cleavage, basal and prismatic yielding hexagonal plates. Before Blowpipe, Etc. — Infusible. On charcoal gives reactions for zinc as described under sphalerite. In closed tube blackens, but is again red on cooling. With borax usually gives amethystine bead. Soluble in hydrochloric acid without effervescence. Similar Species. — Differs from realgar and cinnabar in its asso- ciates, infusibility and slow volatilization. Remarks. — Occurs in quantity only in Sussex County, N. J., at the franklinite lo- calities and is smelted with the associated franklinite, willemite, etc., and the zinc re- covered. GOSLARITE.— Zinc Vitriol. Composition.— ZnSO, -f 7H2O, (ZnO 28.2, SO3 27.9, HjO 43.9 per cent.). General Description. — A white or yellowish earthy mineral with nauseous astrin- gent taste. Usually an incrustration or mass shaped like the original sphalerite or in stalactites. Rarely needle-like orthorhombic crystals. Physical Characters. — Translucent. Lustre, vitreous to dull. Color, white, yellowish, or bluish. Streak, white. H., 2 to 2.5. Sp. gr., 1.9 to 2.1. Before Blowpipe, Etc. — Fuses easily. Yields water in closed tube. With soda gives a white coat and a sulphur test. Easily soluble in water. Remarks. — Goslarite is formed by the oxidation of sphalerite in damp locations. 230 DESCRIPTIVE MINERALOGY. SMITHSONITE.— Dry Bone, Calamine. Composition.— ZnCO,. (ZnO, 648; CO,, 35-2 per cent.). General Description.— Essentially a white vitreous mineral but often colored yellowish or brownish by Fig. 425. iron. Structure stalactitic or botryoidal, or with drusy crystal surface; also in chalky cavernous masses and granular. Sometimes of marked colors as deep green or bright yel- low from copper or cadmium respectively. Crystallization. — Hexagonal. Scalenohedral class p. 39. Axis c = 0.8063. Usually small rhombohedrons of 107°, Fig. 425, like those of siderite. Optically — . Physical Characters. H., 5. Sp. gr., 4.3 to 4.5. Lustre, vitreous to dull. Translucent to opaque. Streak, white. Tenacity, brittle. Color, shades of white, more rarely yellow, green, blue, etc. Cleavage, parallel to rhombohedron (107°). Before Blowpipe, Etc. — Infusible but readily yields white sublimate on coal, often preceded by brown of cadmium. The sublimate becomes yellow when heated and becomes bright green when moistened with cobalt solution and then heated. Soluble in acids with effervescence. Similar Species. — Distinguished from calamine by its efferves- cence and from other carbonates by its hardness. Remarks. — Sniithsonite is a secondary product formed usually by action of carbo- nated waters on other zinc ores and sometimes by atmospheric action. It occurs with the other ores of zinc, especially calamine, and with ores of lead, copper and iron. In this country it is most abundant in the Missouri, Virginia and Wisconsin zinc regions. Uses. — Smithsonite, being easily reduced with little fuel, is a valuable zinc ore, but as it is found chiefly near the surface, the deposits have been nearly exhausted. HYDROZINCITE.— Zinc Bloom. Composition.— ZnCO.,-2Zn(OH)2, (ZnO 75.3, COj 13.6, HjO ii.i per cent.). General Description. — Usually a soft white incrustation upon other zinc minerals, or as dazzling white stalactites, or earthy and chalk like. Physical Characters. — Opaque. Lustre, dull or pearly. Color, pure white to yellowish. Streak shining white. H., 2 to 2.5. Sp. gr., 3.58 to 3.8. ZINC AND CADMIUM MINERALS. 231 Before Blowpipe, Etc. — Infusible. Coats the coal like smithsonite. Yields water in closed tube. Soluble in cold dilute acids with effervescence. WILLEMITE.— Troostite. Composition. — Zn^SiOj, (ZnO, 72.9; SiOj, 27.1); often with much manganese replacing zinc. General Description. — A greenish yellow to apple green or sulphur yellow mineral when pure, but often ^j^ g flesh red or brownish from manganese or iron. ^-;:^^^^r\ Usually occurs granular, but also as hexagonal crystals and massive. The New Jersey variety is known by its associates, franklinite and zincite. Crystallization. — Hexagonal. Class of third order rhombohedron p. 46. Axis c = 0.6775. Long slender prisms of yellowish \Oi.'' — color and coarse thick prisms of flesh red r>^anldin Furnace, N. J. color occur at Franklin Furnace ; the Altenberg crystals are small and brown in color. Physical Characters. H., 5.5. Sp. gr., 3.89 to 4.2. Lustre, resinous. Transparent to opaque. Streak, nearly white. Tenacity, brittle. Color, greenish to sulphur yellow, apple green, white, flesh red. Cleavage, basal and prismatic. Before Blowpipe, Etc. — Fusible in thin splinters only upon the edges to a white enamel. On charcoal with soda and a little borax yields the zinc coat. Soluble in hydrochloric acid leaving a gelatinous residue. Similar Species. — Red crystals resemble apatite but differ in terminations, rhombohedral in willemite but pyramidal in apatite. Willemite is also heavier than apatite and gelatinizes. Uses. — In association with the other minerals of Franklin, N. J., it constitutes a valuable ore of zinc. This, however, is its only important locality. CALAMINE.— Electric Calamine. Composition.— (ZnOH)2Si03, (ZnO, 67.5 ; SiO„ 25.0; H,0, 7.5 per cent.). 232 DESCRIPTIVE MINERALOGY. General Description. — A white or brownish white vitreous mineral frequently with a drusy surface or in radiated groups of crystals, the free ends of which form a ridge or cockscomb, Fig. 428 and, more rarely, small distinct transparent crystals. It oc- curs also granular, stalactitic, botryoidal and as a constituent of clay. Crystallization. — Orthorhombic. Hemimorphic class p. 52. Axes a : b : ^=0.783 : i: 0.478. The crystals are usually tabular, Fig. 427. Fig. 428. Altenberg. Sterling Hill, N. J. the broad face being the brachy pinacoid b while the prism m is relatively small, v is the pyramid 2d:b: 2c. Angles are : mni= 103° 51'; ct= 118° 49'; ii=6g° 48'; vv = 101° 34' Optically + , with acute bisectrix vertical. 2E for yellow light = 78° 39' Physical Characters. H., 4.5 to 5. Sp. gr., 3.4 to 3.5. Lustre, vitreous to pearly. Opaque to transparent. Streak, white. Tenacity, brittle. Color, yellow to brown, white, colorless, rarely blue or green. Cleavage, prismatic. Before Blowpipe, Etc. — Fusible only in finest splinters. With soda and borax, on charcoal yields a white coating, which is made bright green by heating with cobalt solution. In closed tube, yields water. With acids, dissolves, leaving a gelatinous residue. Similar Species. — It is softer than prehnite, harder than cerus- site, and gelatinizes with acids. It differs from willemite in water reaction, and from stilbite in difficulty of fusion. Remarks.— Calamine seems to be formed by the action of hot silica bearing waters upon other zinc ores, especially sphalerite. It is often disseminated through a clay, from which it is gradually segregated and crystallized. Its most important locality in ZINC AND CADMIUM MINERALS. 233 America is at Granby, Mo. It is also found in quantity at Sterling Hill, N. J., and Bertha, Va. Abroad, it is exported from Greece, and is mined in large amounts in Silesia and the Rhenish Provinces of Germany. Uses. — It is a valuable ore of zinc, usually free from volatile impurities. THE CADMIUM MINERALS. The only cadmium mineral is the Sulphide, Greenockite. About five tons per year of cadmium are obtained from the Si- lesian zinc ores. The first fumes are redistilled and finally reduced with carbon. The metal is used in fusible alloys and certain forms of silver plating. The sulphide forms a splendid yellow pigment unaltered by exposure. GREENOCKITE. Composition. — CdS, (Cd, 77.7 per cent.) General Description. — Usually a bright yellow powder upon sphalerite, or a yellow coloration in smithsonite. Very rarely as small hemimorphic hexagonal crys- tals. ^' = 0.8111. Physical Characters. — Translucent. Lustre earthy or adamantine. Color yel- low to orange yellow or bronze yellow. Streait orange yellow. H., 3 to 3.5. Sp. gr., 4.9 to 5.0. Before Biowpipe, Etc. — Infusible, but is easily volatilized in the reducing flame, coating the coal with a characteristic brown coat and a iridescent tarnish. In closed tube, turns carmine red on heating, but is yellow on cooling. Soluble in strong hydrochloric acid, with effervescence of hydrogen sulphide. CHAPTER XXIV. TIN, TITANIUM, AND THORIUM MINERALS. THE TIN MINERALS. The minerals described are : Sulphide, Stannite ; Oxide, Cassit- ERiTE. Tin is also found as an occasional constituent of tantalite and other tantalates. Cassiterite is the only ore of tin, and while it occurs or has been reported from nine or ten states, no tin is now produced* in this country. The world's supply of tin, amounting yearly to about 80,000 long tons, comes chiefly from the East India Islands, Tas- mania, Bolivia and Cornwall, England. The principal use of tin is for the manufacture of tin plate — sheet-iron coated with tin — which is used for canning purposes and in household utensils, etc. It is also largely used in alloys, such as bronze, bell metal, pewter, solder and tin amalgam. Tin- foil is also made from it. The ore as mined is first separated from gangue and impurities by washing, jigging, etc., and if necessary, is then calcined or roasted, to remove volatile elements, such as sulphur, arsenic, antimony. The concentrated and purified ore may then be smelted with car- bon in a shaft furnace. The modern practice is, however, to smelt the ore for several hours in a reverberatory furnace with coal. The liquid tin is drawn off in a float and the slags are resmelted at a higher temperature, frequently requiring the addition of iron or of lime to aid in the separation of the tin, which they still contain. The impure metal obtained is slowly heated to a temperature but little above the melting point of tin ; comparatively pure tin sepa- rates and this is further purified by oxidation. This oxidation is accomplished either by forcing green wood under the liquid metal causing violent agitation or by repeatedly pouring the melted tin in a thin stream frorn ladles. Tin may also be refined by electrol- ysis. *The Temescal mines of California produced about 120 tons from 1890 to 1892 but have since been unproductive. TIN, TITANIUM AND THORIUM MINERALS. 235 STANNITE.— Tin Pyrites. Composition. — (Cu.Sn.Fe)S. Uncertain. General Description. — A massive, granular mineral, of metallic lustre and steel- gray color. It is often intermixed with the yellow chalcopyrite. Physical Characters. — Opaque. Lustre metallic. Color steel gray to nearly black. Streak black. H = 4. Sp. gr., 4.5 to 4.52. Brittle. Before Blowpipe, Etc.— In the reducing flame fuses. In the oxidizing flame yields SOj, and is covered by white oxide, which becomes bluish green when heated with cobalt solution. Soluble in nitric acid to a green solution, with separation of sulphur and oxide of tin. With soda, gives sulphur reaction. CASSITERITE.— Stream Tin. Tin Stone. Composition. — SnOj, (Sn 78.6 per cent.), and usually with some and sometimes TajOj, As^Oj, SiOj or Mn^Oj. FejOa General Description. — A hard and heavy brown to black mineral occurring either in brilliant adamantine crystals or more frequently in dull botryoidal and kidney-shaped masses and rounded pebbles, often with a concentric or fibrous radiated structure. Fig. 429. Fig. 430. Fig. 431. Stoneham, Me. < ^97° 51', cp = 111° 42'. Optically — . Physical Characters. — Transparent to opaque. Lustre, metallic or adamantine. Color, brown, indigo blue, black. Streak, white. H., 5.5 to 6. Sp. gr., 3.82 to 3.95. Brittle. Cleavage, pyramidal and basal. Before Blowpipe, Etc. — As for rutile. Remarks. — After heating the specific gravity becomes 4. 11 to 4.16 or about that of rutile. BROOKITE. General Description. — Either brown translucent crystals which are thin and tabular, or black opaque crystals of varied habit. Fig. 437. Fig. 438. Magnet Cove, Ark. Fig. 439. Ellenville, N. Y. Crystallization. — Orthorhombic. Axes a :i:c'^ 0.842 : i : 0.944. Common forms : unit prism ni with pyramids c := a : i5 : y^c ex e-=i2a:b:c. TIN, TITANIUM AND THORIUM MINERALS. 239 Angles OTOT ^ 99° 50'. zz=;i35°i4'. ee^ioi°2/. Optically -(- with acute bisectrix always normal to face a but plane of optic axes c for red and yellow and b for blue giving characteristic interference figure in white light. Physical Characters. — Translucent to opaque. Lustre, submetallic to ada- mantine. Color, brown, yellow or black. Streak, white or yellow. H., 5.5 to 6. Sp. gr., 3.87 to 4.01. Cleavage, indistinct prismatic and basal. Before Blowpipe, Etc. — As for rutile and octahedrite. THE THORIUM MINERALS. The minerals described are : Phospli'ate (of cerium) monazite ; Silicate, Thorite. The production of monazite sand in North Carohna has greatly decreased owing to the fact that deposits have been found in Brazil which can be had for the cost of gov- ernment taxes and the labor of loading into ships. The sand occurs there in immense deposits, certain beaches consisting of 90 % of monazite. The production of the United States in 1898 was 150,000 pounds.* The oxide of thorium has become exceedingly important of late years through its property of emiting an intense white light when held in the flame of a Bunsen gas burner. The mantle of the Welsbach incandescent gas lamp consists of about 99 % of thorium oxide with one per cent, of cerium oxide. The price of thoria has recently been greatly reduced owing to competition and improved methods of production and to the low price of Brazilian monazite. The chief source of thoria is the phosphate of cerium mineral, monazite. This mineral carries salts of thorium as impurities and in quantities varying from traces to as much as 18.5 % of thorium oxide. The mineral thorite is also employed in the production of thoria, but, although it contains over 20 % of the oxide, it is much more difficult to obtain in quantity. Thoria is manufactured by methods which are generally care- fully guarded. A recent authority f states that the method usu- ally employed is to decompose the monazite sand in hot sul- phuric acid. The sulphates are converted into oxalates from which the thorium oxalate is separated by means of ammonium oxalate, and afterwards transformed into thorium nitrate which on heating yields the oxide. '^ Mineral Industry, Vol. VII., 1899, p. 517. fProf. L. M. Dennis, Minerd Indtistry, Vol. VI., p. 489. 240 DESCRIPTI VE MINER A LOGY. Fig. 440. {" " )\ a.'' / -»-^'' * / 26'; MONAZITE. Composition. — (Ce.La.Di)PO^, but with notable quantities of thorium and silicon and frequently small amounts of erbium and ytterbium. General Description. — Small, brown, resinous crystals, or yellow, translucent grains, disseminated or as sand. Sometimes in angular masses. Crystallization. — Monoclinic. Axes a : b : c^o.g6g : i : 0.926 ; /3 = 76° 20'. Crys- tals are usually small- and flat, but some- times large. Fig. 440 shows the pinacoids a and d, the unit pyramid, prism and dome p, m and o and the prism I == za : b : 00c. Angles ?«;« = 93° ad= 140° 48',//= 106° 41'. Optically -f-, with axial plane nearly a and acute bisectrix nearly vertical. Axial angle in red light 2E= 29° to 31°. Physical Characters. H., 5-5.5. Sp. gr. 4.9-5.3. Lustre, resinous. Opaque, to translucent. Streak, white. Tenacity, brittle. Color, clove brown, reddish brown, yellow. Cleavage, basal, perfect. Before Blowpipe, Etc. Turns gray when heated, but does not fuse. Is decomposed by hydrochloric acid with a white residue. Solutions added to a nitric acid solution of ammonium molybdate produce a yellow precipitate. Remarks. — Monazite is found in considerable quantities in North and South Caro- lina, as sand and as a rock constituent. The Brazilian sand which is now the chief source of supply is found at Eahia, Minas Geraes, Caravellas, San Pedro and Antigua. Uses. — It is the chief source of the thoria used in mantles for in- candescent gas lighting. It is also the chief source of the rare elements cerium, lanthanum and didymium. THORITE.— Orangite. Composition. — -ThSiO^, carrying some water. General Description. — Black or orange yellow tetragonal crystals like those of zircon. Also found massive. Physical Characters. — Translucent to transparent, lustre, resinous, color, black, brown and orange. Streak, orange to brown. Brittle. H., 4.5-5. Sp. gr. 4.8-5.2. Before Blowpipe, Etc. — Infusible. Gelatinizes with hydrochloric acid before being heated by blowpipe but not after. In closed tube yields water and the orange variety becomes nearly black while hot, but changes to orange again on cooling. Remarks. — Occurs chiefly in Norway. Uses. — Is a source of thoria, but less important than monazite. CHAPTER XXV. LEAD AND BISMUTH MINERALS. THE LEAD MINERALS. The minerals described are : Metal, Lead ; Sulphides and Selen- ides, Galenite, Bournonite, Jamesonite, Clausthalite ; Oxides, Minium ; Sulphates, Anglesite, Linarite; Phosphate, Pyromor- PHiTE ; Arsenate, Mimetite ; Carbonates, Cerussite and Phosgen- ITE ; Chromate, Crocoite ; Vanadates, Vanadinite, Descloizite ; Molybdate, Wulfenite ; Tungstate, Stolzite. The most important ores of lead are galenite and cerussite. The world uses nearly 800,000 tons of lead per year, of which this country, in 1899, produced 213,003 tons.* Of this about one- quarter was soft lead, mainly produced in Missouri and Kan- sas, containing almost no silver and gold. During the same year one half of the total output of lead was desilverized ; indeed, it may be said that by far the most important use of lead ore is to mix and smelt with silver ores whereby metallic lead containing silver and gold is obtained. The principal use of metallic lead is in the manufacture of white lead, 103,282 tons being produced in 1899 in the United States alone. Large amounts are also used for the preparation of red lead, litharge, shot, lead pipe and sheet lead. A certain amount of lead containing antimony is used in type and in alloys for friction- bearings. The argentiferous lead ores of the west, which ordinarily run low in lead are smelted in blast-furnaces. The ore, if it contains much sulphur, is roasted, to remove the sulphur and other volatile constituents, and is then fused, forming a silicate, which is charged in the furnace with the proper proportions of fuel and flux (lime- stone, hematite, etc.). The reduction takes place under the action of the blast. Metallic lead, carrying most of the silver, is pro- duced, and if either sulphur or arsenic is present, a suljDhide (matte) * Engineering and Mining Journal, 1900, p. 2, 242 DESCRIPTIVE MINERALOGY. and an arsenide (speiss) of iron, copper, etc., will form, and above all these will float the slag composed of the gangue and the flux. The furnace is usually oblong in section, and the hearth is con- nected, by a channel from the bottom, with an outer basin or well, so that the metal stands at the same level in each and can easily be ladled out. Above the hearth, and enclosing the smelting zone, are what are called the water-jackets, in which cold water cir- culates. The furnace gases pass through a series of condensing chambers. The matte, speiss and the dust collected in the condensing cham- bers are all treated for silver, gold, lead, copper, etc., usually at different works. The metallic lead, or base bullion, is desilverized by remelting in large kettles, raising it to the melting-point of zinc, adding metallic zinc and cooling to a point between the melting- points of zinc and lead. The lighter solidified zinc separates, carry- ing with it the silver, and forms a crust on the surface of the lead, from which it is skimmed. The lead is further purified and the zinc and silver separated electrolytically or by distillation. LEAD.— Native Lead. Composition. — Pb, with sometimes a little Sb or Ag. General Description. — Usually small plates or scales or globular masses em- bedded in other minerals. Very rarely in octahedrons or dodecahedrons. Physical Characters. — Opaque. Lustre metallic. Color and streak lead gray. H., 1.5. Sp. gr., H.37. Malleable. Before Blowpipe, Etc. — Fuses easily, coating charcoal with yellow oxide, and tinging flame light blue. Soluble in dilute nitric acid. GALENITE. — Galena. Composition. — PbS, (Pb 86.6 per cent.) usually with some silver and frequently sulphide of antimony, bismuth, cadmium, etc. General Description. — A soft, heavy, lead-gray mineral, with metallic lus- tre and easy cubical cleav- age. Sometimes in crys- tals. Rarely fine-grained or fibrous. Crystallization. — Iso- metric. Usually the cube a or cubo-octahedron a p, sometimes octahedral or showing Joplin, Mo. LEAD AND BISMUTH MINERALS. 243 that rare form the trigonal trisoctahedron r = a : a: 2a, Fig. 444. Sometimes twinned or in skeleton crystals or reticulated. Fig. 442. Fig. 443. Fig. 444. Physical Characters.- LusTRE, metallic. Streak, lead- gray. Color, lead-gray. -H., 2.5. Sp. gr., 7.4 to 7.6. Opaque. Tenacity, brittle. Cleavage, cubic, very easy. Before Blowpipe, Etc. — On charcoal decrepitates and fuses easily, yielding in O. F. a white sulphate coat, and in R. F. a yellow coat and metallic button of lead. With bismuth flux, gives a strong iodide coat, which appears chrome-yellow on plaster and greenish- yellow on charcoal. With soda, yields malleable lead and a sul- phur test. Soluble in excess of hot hydrochloric acid, from which white lead chloride separates on cooling. Soluble also in strong nitric acid, with separation of sulphur and lead sulphate. Similar Species. — Characterized by its cleavage, weight and appearance, except in some fine-grained varieties. Remarks. — Galenite is the common and parent ore of lead. It occurs with other sulphides, especially sphalerite, pyrite and chalcopyrite, with a gangue of quartz, fluorite, barite or calcite. Also with ores of silver and gold. It changes easily to cerussite, anglesite and other lead minerals. Besides the silver-producing States of Colorado, Utah and Montana, which also produce the most lead, Kansas, Wisconsin and Mis- souri manufacture much soft lead from their deposits of galenite. Uses. — It is the chief ore of lead, and as it usually contains silver, the silver-bearing deposits are more frequently worked than the purer galenite, and both the lead and silver are recovered. BOURNONITE. Composition. — PbCuSbSj, (Pb 42.5, Cu 13.0, Sb 24.7, S 19 8 per cent.). General Description. — A gray metallic mineral, nearer steel-gray than galenite, and occurring fine-gi'ained, massive and in thick tabular crystals. More like tetra- hedrite than galenite when massive. 244 DESCRIPTIVE MINERALOGY. Crystallization. — Orthorhombic. Axes a: b: ^ ^0.938: i i.o.Sgy. Common forms the pinacoids a, h, c, the unit domes and prism d, 0, and «, and the pyramid u^ir. 1>: yi c. Short prismatic or tabular, with vertically striated faces, or, in cross, Fig. 446, and "cog-wheel" twins. Angles ?»?» = 93° 40', f = 136° 17', cu=n(>° AS'- Fig. 445. Fig. 446. ^' t -.-.-^.- TJ^ t m t m ^ Harz Kapnik. Physical Characters. — Opaque. Lustre, metallic. Color, steel-gray to nearly black. Streak, steel-gray. H,, 2.5 to 3. Sp. gr., 5.7 to 5.9. Brittle. Cleavages im- perfect. Before Blowpipe, Etc. — On charcoal, fuses easily, yielding heavy white sublimate, and later a yellow sublimate. With bismuth flux yields strong greenish-yellow coat on charcoal and a mingling of chrome yellow and peach red on plaster. After sublimates have formed, the residue will color the flame deep green, or if moistened with a drop of hydrochloric acid, will color the flame bright azure blue. Soluble in iiitric acid to a green solution, with formation of a white insoluble residue. JAMESONITE.— Feather Ore. Composition. — PbjSbjSs, (Pb 50.8, Sb 29.5, S 19.7 per cent.). General Description. — Steel-gray to dark-gray metallic needle crystals, or hair- like and felted; also compact and fibrous massive. Physical Characters. — Opaque. Lustre, metallic. Color, steel-gray to dark- lead gray. Streak, grayish-black. H., 2 to 3 ; Sp. gr., 5.5 to 6. Brittle. Before Blowpipe, Etc. — Decrepitates and fuses very easily, and is volatilized, coating the charcoal white and yellovv as in bournonite. With bismuth flux, reacts like bournonite. In closed tube, yields dark-red sublimate, nearly black while hot. Soluble in hot hydrochloric acid, with effervescence of hydrogen sulphide. CLAUSTHALITE. Composition. — PbSe, (Pb 72.4, Se 27.6 per cent.). May contain silver or cobalt. General Description. — Bluish gray fine granular masses of metallic lustre. Rarely foliated. Resembles galenite. Physical Characters.— Opaque. Lustre, metallic. Color, bluish lead gray Streak, grayish black. H., 2.5 to 3. Sp. gr;, 7.6 to 8.8. Before Blowpipe, Etc.— -On charcoal fuses and yields odor like decayed horse- radish, coats the charcoal with a white sublimate with red border, and later a yellow coat forms. In open tube gives a red subUmate. With soda yields a mass which blackens silver. MINIUM. Composition. — PbjO^, (Pb 90.6 per cent.). General Description. — A vivid red powder or loosely compacted mass of dull or greasy lustre. Often intermixed with yellow. Physical Characters. — Opaque. Bright red. Lustre, dull or greasy. Streak, orange yellow. H., 2 to 3, Sp. gr., 4,6, LEAD AND BISMUTH MINERALS. 245 Before Blowpipe, Etc. — Is reduced to metallic lead, and yields the characteristic lead sublimates. Remarks. — The artificial product is the red lead of commerce. ANGLESITE. Composition. — PbSO^, (PbO 73.6, SO3 26.4 per cent.). General Description. — A very brittle, colorless or white mineral of adamantine lustre, sometimes colored by impurities. Usually massive, frequently in concentric layers around a core of unaltered galenite. Fig. 447. Fig. 448. Phoenixville, Pa. Crystallization. — Orthorhombic. Axes a:b:c = 0.785 : i : 1.289. Crystals vary greatly in type, but are rarely twinned. Unit prism m and domes such as 11 = a : k> b : y^c, z = a: cab: y^c and pyramids q = 2a : b : c are frequent. Angles: umi= 103° 43 >^'; <:« = 146° 36^'; cz = 157° 41'; cq = 123° 12'. Optically + , with high indices of refraction 1.877, 1.882 and 1.893 for yellow light. Axial plane is the brachy pinacoid b. Physical Characters. H., 3. Sp. gr., 6.12 to 6.39. Lustre, adamantine to vitreous. Transparent to opaque. Streak, white. Tenacity, very brittle. Color, colorless, white, gray ; rarely yellow, blue or green. Cleavage, basal and prismatic (90° and 103° 43'). Before Blowpipe, Etc. — On charcoal decrepitates and fuses easily to a glassy globule pearly white on cooling. In R. F. is re- duced and yields metallic lead and the yellow sublimate. With soda yields the sulphur reaction. Insoluble in hydrochloric acid but is converted into chloride. Slowly soluble in nitric acid. Similar Species. — It differs from the carbonate, cerussite, in absence of twinned crystals and of effervescence in acids. It is heavier than barite and celestite, and yields lead. 246 DESCRIPTIVE MINERALOGY. Remarks.— Anglesite is formed by the oxidation of galenite. It alters to the car- bonate, cerussite, by interchange with calcium carbonate in solution. It is found throughout the United States wherever exposed deposits of galenite occur. The lead mines of Missouri, Wisconsin, Colorado, etc., all contain this mineral. It occurs in large quantities in Mexico and Australia. Uses. — It is an ore of lead. LINARITE. Composition.— [(Pb. Cu)OH],S04, (PbO 55.7, CuO 19.8, SO3 20.0, H2O 4.S per cent.). General Description.— Small deep blue translucent crystals. Often tabular. Monoclinic. Physical Characters. — Translucent. Lustre, vitreous or adamantine. Color, deep azure blue. Streak, pale blue. H., 2.5. Sp. gr., 5.3 to 5.45. Brittle. Cleav- ages at 77° to each other. Before Blowpipe, Etc.— Loses color and fuses easily to a pearly glass. In R. F. is reduced to metal yielding yellow coat and ultimately red button, which when moistened with hydrochloric acid will color flame deep blue. Soluble in nitric acid with separation of lead sulphate. PYROMORPHITE. Composition.— 3Pb,(PO,)3.PbCl2(PbO 82.2, P^O^ 15.7, CI 2.6 per cent.) often with some As, Fe or Ca. General Description. — Short hexagonal prisms and branch- ing and tapering groups of prisms in parallel position. The color is most frequently green, brown, or gray. Also in moss-like in- terlaced fibres and masses of imperfectly developed crystals. Less frequently in globular and reniform masses. 449- Fig. 450. Oberlahnstein. Crystallization. — Hexagonal Class of third order pyramid, p. 37. Axis c = 0.736. Usual form prism m and base c. Faces m horizontally striated, sometimes tapering. LEAD AND BISMUTH MINERALS. 247 Physical Characters. H., 3.5 to 4. Sp. gr., 5.9 to 7.1. Lustre, resinous. Translucent to opaque. Streak, white to pale yellow. Tenacity, brittle. Color, green, gray, brown ; also yellow, orange, white. Before Blowpipe, Etc. — On charcoal fuses to a globule which on cooling does not retain its globular form but crystallizes, show- ing plane faces. In reducing flame yields white coat at a distance and yellow coat nearer the assay, and a brittle globule of lead. In closed tube with magnesium ribbon yields a phosphide which, moistened with water, evolves phosphine. With salt of phos- phorus saturated with copper oxide yields an azure blue flame. Soluble in nitric acid, and from the solution ammonium molyb- date throws down a yellow precipitate. Similar Species. — Differs from other lead minerals in fusing to a crystalline globule without reduction. Remarks. — Probably formed from galeiiite. Occurs with other lead minerals. Found at Phcenixville, Pa., Davidson county, N. C, Lenox, Me., and many other localities. MIMETITE. CoMPOsmoN.-3Pb3(As04)j-f PbCl, or Pb5Cl(As04)3, (PbO 74.9, As^Oj 23.2, CI 2.39 per cent.), often with some replacement by P or Ca. General Description. — Pale yellow to brown hexagonal prisms or globular groups of crystals. Sometimes incrusting. Fig. 451. Physical Characters. — Translucent. Lustre, resin- ous. Color, yellow, brown or white. Streak, white. H., 3.5. Sp. Gr., 7.0 to 7.25, lower when Ca is present. Before Blowpipe, Etc. — On charcoal fuses easily and is reduced to metallic lead, coating the coal with white and yellow sublimates and yielding strong arsenical odor. Phosphorus, if present, and chlorine may be detected as in pyromorphite. CERUSSITE. -White Lead Ore. Composition. — PbCOa, (PbO, 83.5 ; CO2, 16.5 per cent). Often carries silver. General Description. — Very brittle, white or colorless ortho- rhombic crystals; silky, milk-white masses of interlaced fibres; granular, translucent, gray masses and compact or earthy, opaque masses of yellow, brown, etc., colors. Crystallization. — Orthorhombic. Axes d:b:c= 0.610: i : 0.723. Common forms : unit pyramid /, and prism m and a series 248 DESCRIPTI VE MINERALOG Y. of brachy domes such as ;tr = co d : d : y^c, w =: 00 a : b : 2c and V = a : b : y. Frequently twinned about in sometimes yield- ing six rayed groups as in Fig. 453. Common angles are mm = 117° 14', J>p=iT,o°, WW = 69° 20'. Fig. 452. Fig. 453. Black Hawk, Mont. Transbaikal. Optically — . Axial plane b and acute bisectrix normal to c. High indices of refraction : 1.804, 2.076, 2.078 in yellow light. Physical Characters. H., 3 to 3.5. Sp. gr., 6.46 to 6.51. Lustre, adamantine, pearly, Transparent or translucent, sometimes silky. Streak, white. Tenacity, very brittle. Color, white, gray, colorless or colored by impurities. Cleavages, parallel to prism and brachy dome. Before Blowpipe, Etc. — On charcoal, decrepitates, fuses and gives a yellow coating, and finally a metallic globule. In closed tube, turns yellow, then dark, and on cooling is yellow. Effer- vesces in acids, but with hydrochloric or sulphuric acid leaves a white residue. Similar Species. — Distiriguished from anglesite by efferves- cence in acids and by frequent occurrence of twinned crystals. Has higher specific gravity than most carbonates. REMARKS.-:-Cerussite is derived from galenite by the action of water containing carbon dioxide. It may also be produced from anglesite by action of a solution of calcium carbonate. Uses. — It is smelted for lead and silver, and a process exists for the direct manufacture of white lead from cerussite. PHOSGENITE. Composition.— PbjCljCOj, (PbO, 81.9; €1,13.0; CO2, 8.1 per cent.). General Description.— Large and small tetragonal crystals, usually prismatic and colorless ; sometimes gray and translucent. LEAD AND BISMUTH MINERALS. 249 ' Physical Characters. — Transparent to translucent. Lustre, adamantine. Color, colorless, white, gray or yellow. Streak, white. H„ 3. Sp. gr., 6 to 6.1. Cleaves parallel to both prisms and the base. Before Blowpipe, Etc. — Fuses easily to a yellow globule. On charcoal, is re- duced to metal and forms chiefly a white coating of lead chloride. Soluble in nitric acid with effervescence. CROCOITE. Composition.— PbCrO^, (PbO, 68.9; CrOj, 31.1 per cent.). General Description. — Bright hyacinth-red mineral, usually in raonoclinic pris- matic crystals, but also granular and columnar. The color is like that of potassium dichromate. Physical Characters. — Translucent. Lustre, adamantine. Color, hyacinth red. Streak, orange yellow. H., 2.5 to 3. Sp. gr., 5.9 to 6.1. Sectile. Cleavage, prismatic. Before Blowpipe, Etc. — In closed tube, decrepitates violently, becomes dark, but recovers color cm cooling. Fuses very easily, and is reduced to metallic lead with deflagration, the coal being coated Avith a yellow sublimate. With borax or S.Ph., forms yellow glasses, which are bright green when cold. Soluble in nitric acid to a yellow solution. Fused with KHSO4 on platinum, yields a dark-violet mass, red on solidifying and greenish.white when cold which distinguishes it from vanadinite. VANADINITE. Composition.— 3Pb3(V04VPbCl2 or PbjCKVOJj, (PbO, 78.7; V2O5, 194; CI, 2.5 per cent.), often with P or As replacing V. General Description. — Small, sharp, hexagonal prisms, some- times hollow, of bright-red, yellow or brown color. Also parallel groups and globular masses of crystals. Crystallization. — Hexagonal. Class third order pyramid, p. 37. Axis (j = 0.712. Simple prism ni with base c, or more rarely with pyramid p and tldrd order pyramid v = ^a : 3a : a: y, Fig. 455. Fig. 454. Fig. 455. \JkJ Physical Characters. H., 3. Sp. Gr., 6.66 to 7.23. Lustre, resinous on fracture. Opaque, or translucent. Streak, white to pale yellow. Tenacity, brittle. Color, deep red, bright red, yellow or brown. 250 DESCRIPTIVE MINERALOGY. Before Blowpipe, Etc. — Fuses easily on charcoal to a black mass, yielding a yellow sublimate in the reducing flame. The residue gives deep-green bead, with salt of phosphorus in the re- ducing flame. With strong nitric acid the. substance becomes deep red, then dissolves to a yellow solution. Fused with KHSO4, yields a clear yellow, then a red, and finally yellow when cold. Uses. — It is the source of vanadium, for vanadium black ; for vanadium salts, which are used as a mordant in the manufacture of the finest silks; for vanadium bronze and for vanadium ink. DESCLOIZITE. Composition. — (Pb.Zn)(PbOH),V04, (PbO, 55.4; ZnO, 19.7; V^Oj, 22.7; HjO, 2.2). General Description. — Small purplish-red, brown or black crystals, forming a drusy surface or crust. Also fibrous, massive. Physical Characters. — Transparent to nearly opaque. Lustre, greasy. Color purplish red, brown or black. Streak, orange or brown. H., 3.5. Sp. gr., 5.9 to 6.2. Before Blowpipe, Etc. — On charcoal, fuses to black mass, enclosing metal. In closed tube yields water. Vanadium reactions as in vanadinite. ^VULFENITE. Composition. — PbMoO^, sometimes containing Ca, Cr. V. General Description. — Usually in thin, square, tabular crys- tals of yellow, orange or bright orange-red color and resinous lustre. Less frequently in granular masses or acute pyramidal crystals. Crystallization. — Tetragonal. Class of hemi- morphic pyramid/. Axis ^=1.577. Usually the base c with the pyramid Extensive de- posits exist at Pereta, Tuscany. 26o DESCRIPTIVE MINERALOGY. SENARMONTITE. Composition. — Sb^Oj, (Sb, 83.3' per cent.). General Description. — Colorless to gray octahedral crystals and granular masses. Physical Characters. — Transparent to translucent. Lustre, resinous. Color, colorless or gray. Streak, white. H., 2 to 2.5. Sp. gr., 5.22 to 5.30. Before Blowpipe, Etc. — Fuses easily, coating the charcoal with white oxide. In R. F. is reduced, but again oxidizes and coats the coal, coloring the flame green. Solu- ble in hydrochloric acid. Remarks. — Formed by oxidation and decomposition of stibnite and other ores of antimony. VALENTINITE. Composition. — SbjOj, (Sb, 83.3 per cent.). General Description. — Small white flat crystals (orthorhombic) or fan-shaped groups of a somewhat silky lustre and white or gray color. Also in spheroidal masses with radiated lamellar structure. Physical Characters. — Translucent. Lustre, adamantine or silky. Color, white, gray, pale red. Streak, white. H., 2.5 to 3. Sp. gr., 5.57. Before Blowpipe, Etc. — As for senarmontite. THE URANIUM MINERALS. The minerals described are : Uranate, Uraninite ; Phosphates, AUTUNITE, TORBERNITE. The metal uranium has a limited use in uranium steel, as a small percentage of uranium increases the elasticity and hardness of or- dinary steel. A few tons of sodium uranate, commercially known as uranium yellow are used yearly in coloring glass yellow with a greenish reflex, and in coloring porcelain orange or black. A small amount is used in photography. URANINITE.— Pitch Blende. Composition.— A uranate of UO^, Pb, etc., and may contain Ca, N, Th, Zr, Fe, Cu, Bi, etc. General Description.— A black massive mineral of botryoidal or granular structure and pitch-like appearance. Rarely in small isometric crystals. Physical Characters. H., 5.5. Sp. gr., 5 to 9.7. Lustre, pitch-like, submetallic. Opaque. Streak, gray, olive green, dark brown. Tenacity, brittle. Cqlor, some shade of black. Before Blowpipe, Etc.— Infusible or very slightly fused on ARSENIC, ANTIMONY, ETC., MINERALS. 261 edges, sometimes coloring the flame green from copper. On char- coal with soda may yield reaction for lead, arsenic and sulphur. In borax yields a green bead made enamel black by flaming. Soluble in nitric acid to a yellow liquid from which ammonia throws down a bright yellow precipitate. Similar Species. — The appearance and streak are frequently sufficient distinctions. The bead tests are characteristic. Remarks. — Uraninite occurs both in granitic roclcs and in metallic veins. It is frequently associated with minerals resulting from its decomposition and with metallic ores. It is mined at Joachimstal, Bohemia, from whence the principal supply is obtained. It occurs in Jefferson and Gilpin counties, Colorado, having been mined at Central City and is found also in some quantity in Mitchell county, N. C, at Marietta, S. C, in Texas, and in the Black Hills of South Dakota. Uses. — Uraninite is the chief source of the uranium salts used in painting on porcelain and in the manufacture of a fluorescent glass of yellowish-green color. AUTUNITE— Lime Uranite. COMPOSITION:— Ca(UOa)2(P04)2-f8H20, (UO3 62.7, CaO 6.1, PjOj 15.5, H2O15.7 per cent.). General Description. — Little square(/A/90°43') orthorhombic plates of bright yellow color and pearly lustre, or in micaceous aggrep'ates. Physical Characters. — Translucent. Lustre, pearly on base. Color, lemon to sulphur yellow. Streak, pale yellow. H., 2 to 2.5. Sp. gr., 3.05 to 3.19. Brittle. Cleavage basal. Before Blowpipe, Etc. — On charcoal fuses with intumescence to a black crystal- line globule. With salt of phosphorus or borax in the reducing flame yields a green bead. Dissolves in nitric acid to a yellow solution. TORBERNITE.— Copper Uranite. Composition.— Cu(U02)j(PO,)2 -|- SH^O, (UO, 61.2, CuO 8.4, vp^ 15. i, H.p 15.3 per cent.). General Description.— Thin square tetragonal plates of bright green color and pearly lustre. Sometimes in pyramids or micaceous aggregates. Physical Characters. — Translucent. Lustre, pearly. Color, emerald to grass green. Streak, pale green. H., 2 to 2.5, Sp. gr., 3.4 to 3.6. Brittle. Before Blowpipe, Etc.— Fuses easily to a black mass and colors the flame green. In borax yields a green glass in O. F., which becomes opaque red in R. F. Soluble in nitric acid to a yellowish green solution. THE MOLYBDENUM MINERALS. The minerals described are : Sulphide, Molybdenite ; Oxide, MoLYBDiTE. Besides these molybdenum occurs as the acid con- stituent of Wulfenite elsewhere described. 262 DESCRIPTIVE MINERALOGY. The metal has a limited use in the production of an alloy with steel. Its chief important compounds are sodium molybdate used to impart a blue color to pottery and in dyeing silks and woolens, and molybdic acid from which useful chemical reagents are pre- pared in the laboratory. MOLYBDENITE. Composition.— M0S2, (Mo 60.0, S 40.0 per cent). General Description. — Thin graphite--like scales or foliated masses of metallic lustre and bluish gray color, easily separated into flexible non-elastic scales. Sometimes in tabular hexagonal forms and fine granular masses. Soft, unctuous and marks paper. Physical Characters. H., i to 1.5. Sp. gr., 4.6 to 4.9. Lustre, metallic. Opaque. Streak, greenish.* Tenacity, sectile to malleable. Color, bluish lead gray. Cleavage, basal. Before Blowpipe, Etc. — In forceps infusible, but at high heat colors the flame yellowish green. On charcoal gives sulphurous odor and slight sublimate, yellow hot, white cold, and deep blue when flashed with the reducing flame. Soluble in strong nitric acid and during solution on platinum it is luminous. With sul- phuric acid yields a blue solution. In salt of phosphorus and borax yields characteristic molybdenum reactions. Similar Species. — ^Differs from graphite in streak and blowpipe reactions. May usually be distinguished by its lighter bluish gray color. Remarks. — Occurs usually in crystalline rocks, and is not readily altered. It is found in many American localities, but is not mined. Westmoreland, N. H., Blue Hill Bay, Maine, and Pitkin, Colorado, have probably the largest American deposits. Uses. — It is the source of the molybdenum salts which are im- portant chiefly in analytical work. MOLYBDITE. Composition. — M0O3, (Mo 66.7 per cent.). General Description. — An earthy yellow powder or, rarely, tufts and hair-like crystals of yellowish-white color. Physical Characters. — Opaque to translucent. Lustre, dull or silky. Color, yellow or yellowish white. Streak, straw yellow. H., I to 2. Sp. gr., 4.49 to 4.5. Before Blowpipe, Etc. — On charcoal fuses, yielding crystals yellow hot, white cold, and made deep blue by the reducing flame. In borax and salt of phosphorus gives characteristic molybdenum reactions. * Best seen on glazed porcelain. CHAPTER XXVII. THE COPPER MINERALS. The minerals described are : Metal, Copper ; Sulphides, Chal- cociTE, BoRNiTE, Chalcopyrite ; Sidphoarsenides, Enargite, Ten- NANTiTE ; $ulphoantimonides , Tetrahedrite ; Oxides, Cuprite, Tenorite ; Oxychloride, Atacamite ; Sulphates, Chalcanthite, Brochantite ; Phosphate, Libethenite ; Arsenate, Olivenite ; Carbonates, MAtACHiTE, Azurite ; Silicates, Chrysocolla, Diop- TASE. In addition to these the iron sulphides often carry copper which is extracted after burning for sulphuric acid. The chief copper minerals are chalcopyrite and bornite, native copper, cuprite, malachite and azurite, though with the exception of two or three, all the others above mentioned are sufficiently plentiful to be considered as ores. The world's product* of cop- per in 1898 was 434,329 long tons of which this country produced 239,241 tons. In 1 899 the output of the United States had increas- ed to 264,586 tonsf, and of the total product of the world, about one- fourth was derived from the sulphide ores of Montana, and one-sixth from the native copper of Michigan. Altogether, the United States yields about two-thirds of the copper annually produced. The method of extraction of the copper is dependent upon the nature of the ore, and ma> roughly be classed under three headings : Treatment of native copper. Treathient of oxidized ores. Treatment of sulphides. A great many processes exist or have existed, but these for a general brief discussion may be reduced to a small number of type processes of which the others are variations due to local conditions or constituents of the ore. Treatment of Native Copper. Native copper occurs m enormous quantities in Michigan, and the deposits mined average less than two per cent, of copper, al- though occasionally large masses of the metal are found. The rock is crushed by steam stamps and the copper separated from * Mineral Industries, 1899, pp. 213 eiseq. i; Engineering and Mining Journal, 1900, p. 2. 264 DESCRIPTIVE MINERALOGY. the rock by the action of water and the use of jigs, tables, and other concentrating apparatus. The concentrated material is then melted in a large re verberatory furnace with limestone and slags from previ- ous operations. The new slag thus formed contains the remain- ing rock and is removed, leaving behind copper, which after a period of reduction by charcoal and stirring is cast into ingots. Treatment of Oxidized Ores. The oxidized ores in Arizona which average over ten per cent, of copper, are smelted in blast-furnaces with coke and the neces- sary flux to make a slag with the associated gangue. The result is an impure metal called black copper, which is later refined. Treatment of Sulphides. The treatment of sulphides is quite varied, depending chiefly on the presence or absence of arsenic, the richness of the ore and the local conditions. The ores always contain iron, copper and sul- phur, and may contain arsenic, antimony, silver, gold, etc. All the smelting processes depend on the facts that at high tempera- tures copper has a greater affinity for sulphur than iron has, and iron a stronger affinity than copper for oxygen. So that if such an ore is subjected to oxidation by roasting, oxides result ; but in the subsequent fusion, if enough sulphur has been left, the copper will form a fusible sulphide, and the oxidized iron will unite with the gangue and the flux to form a slag. By regulating the roasting, the sulphur contents may be brought to any desired percentage. This may be just sufficient to satisfy the copper or to satisfy also a great deal of the iron producing a low-grade sulphide (matte), which, by re-roasting and refusion, is enriched. The low-grade matte means a smaller loss of copper in the slags, and is often of service in assisting the removal of ar- senic and antimony. When the matte has reached the required percentage of copper, it is roasted as free from sulphur as possible, and being now essen- tially an oxide, it may be smelted for copper either in a shaft-fur- nace, much as the oxidized ores are, or, when silver or gold is present, in a reverberatory furnace. In a more recent method the ores are roasted and fused, pro- ducing a matte containing over fifty per cent, of copper. This matte, while liquid, is run into a sort of Bessemer converter, and 2HE COPPER MINERALS. 26:; a blast turned on, by which the sulphur, arsenic and antimony- are driven off, the iron oxidized and converted into slag, and black copper obtained. The crude copper is refined either by remelting and oxidation, or more frequently electrolytically. The great uses of copper are in electrical work and in alloys with zinc and tin, such as brass, yellow metal, bronze, bell metal, German silver, etc. In 1 899 about 30,000 tons of copper sulphate were made in the United States. COPPER. Composition. — Cu often containing Ag, sometimes Hg or Bi. General Description. — A soft, red, malleable metal, with a red streak. Usually in sheets or disseminated masses, varying from small grains to several hundred tons in weight. Also in threads and wire and in distorted . 1 1 i ■ i 1 Lake Superior. crystals and twisted groups. Crystallization. — Isometric. Tetrahexahedron and cube most frequent, also twinned, Fig. 466, giving by elongation spear-shaped forms often complexly grouped and usually distorted. See Fig. 3 1 2. Fig. 464. Fig. 465. Fig. 466. Fig. 463. ^±2=:^^ -- ^_-: _a. Lake Superior. Physical Characters. H., 2.5 to 3. Sp. gr., 8.8 to 8.9. Lustre, metallic. Opaque. Streak, copper red, Tenacity, malleable and ductile. Color, copper red, tarnishing nearly black. Before Blowpipe, Etc. — Fuses easily to a malleable globule, often coated with a black oxide. In beads, becomes in O. F. green when hot; blue, cold, and in R. F. opaque red. Soluble in nitric 266 DESCRIPTIVE MINERALOGY. acid, with evolution of a brown gas, to a green solution, which will deposit copper on iron or steel. The solution becomes deep azure blue on addition of ammonia. Similar Species. — Resembles niccolite and tarnished siiver, differs in copper-red streak. , Remarks. — Occurs with native silver and ores of copper, and by oxidation may form cuprite or melaconite or the carbonates. In Michigan it occurs in trap or conglomerate. It is especially apt to occur near dikes of igneous rocks. The great locality of the world for native copper, and the only locality still yielding this mineral in large quantities, is the Lake Superior region of Northern Michigan, and although the territory here covered is many square miles in extent, the Calumet and Hecla mine yields the major part of all that is produced. Although native copper is also found in Arizona, California, and, to a limited extent, in other American locali- ties, it is never mined for itself alone, nor does it constitute a large part of the copper ore present. The Coro-Coro mines, in Bolivia, are now producing some copper from the native metal. Uses. — It is an important source of the copper of commerce. CHALCOCITE.— Copper Glance. Composition. — CujS, (Cu 79.8, S 20.2 per cent.). General Description. — Black granular or compact masses, with metallic lustre or sometimes nodules or pseudomorphic after wood. Often coated with the green carbonate, malachite. Also in crystals. Crystallization. — Orthorhombic, ^ : (^ : ^ = 0.582 : i : 0.970. T A /= 1 19° 35'. O f\ 1 = 117° 24>^'. Tabular forms, pseudo- hexagonal or frequently twinned, making star-like groups. Physical Characters. H., 2.5 to 3. Sp. gr., 5.5 to 5.8. Lustre, metallic. Opaque. Streak, lead gray.- Tenacity, brittle. Color, blackish lead gray, with dull-black tarnish. Before Blowpipe, Etc. — On charcoal, fuses to a globule, yield- ing sulphur dioxide. With soda, yields a copper button and a strong sulphur reaction. Colors flame emerald green, or if moist- ened with hydrochloric acid, it colors the flame azure blue. In borax or salt of phosphorus, yields copper beads. Soluble in nitric acid, leaving a residue of sulphur. Similar Species. — It is more brittle than argentite, and differs from bornite in not becoming magnetic on fusion. Remarks. — Chalcocite occurs with other copper minerals and with hematite, THE COPPER MINERALS. 267 galenite and cassitevite. Is found at Butte, Montana, and other American localities of less importance. Fine crystals are obtained from Cornwall, England. Uses. — It is an ore of copper. BORNITE.— Purple Copper Ore. Horse Flesh Ore. Composition. — Cu3FeS3, (Cu 55.5, Fe 16.4,528.1 per cent), but often contains admixed chalcocite. General Description. — On fresh fracture, bornite is of a pecu- liar red-brown color and metallic lustre. It tarnishes to deep blue and purple tints, often variegated. Usually massive, sometimes small cubes or other isometric forms. Physical Characters. H., 3. Sp. gr., 4.9 to 5.4. Lustre, metallic. Opaque. Streak, grayish black. Tenacity, brittle. Color, dark copper red, brownish or violet blue, often varied. Before Blowpipe, Etc. — Blackens, becomes red on cooling, and finally fuses to a brittle, magnetic globule and evolves sulphur dioxide fumes. In oxidizing flame with borax or salt of phos- phorus, gives green bead when hot, greenish blue when cold, the bead is opaque red in the reducing flame. Soluble in nitric acid, with separation of sulphur. Remarks. — On account of its high percentage of copper, it is especially valuable as an ore of copper when found in quantity. A large portion of the ore of many of the Chilian mines consists of bornite, and it has been found in quantity in the Montana copper regions. Also found at Bristol, Conn. ; Acton, Canada : in Mexico, in Peru and other copper regions. Uses. — It is an important ore of copper. CHALCOPYRITE.— Copper Pyrites. Yellow Copper Ore. Composition. — CuFeSj, (Cu 34.5, Fe 30.5, S 35.0 per cent), with mechanically intermixed pyrite at times. General Description. — A bright brassy yellow mineral of metallic lustre, often with iridescent tarnish resembling that of bornite. Usually massive. Sometimes in crystals. Crystallization. — Tetragonal. Scalenohedral class p. 31. Axis c = 0.985. Sphenoids predominate / = unit sphenoid ; o = a:a:'^c \ t=a:a:\c; v = a : a : 4c ; s=a:2a:c Angles (over top) pp=Ti° 20'; oo = 51° 8'; tt = 141° 35'; vv = 20" 21'. 268 DESCRIPTIVE MINERALOGY. Fig. 467. . Fig. 468. Fig. 469. French Creek, Pa. H., 3.5 to 4. EUenville, N. Y. Physical Characters. H., 3.5 to 4. Sp. gr., 4.1 to 4.3. Lustre, metallic. Opaque. Streak, greenish black. Tenacity, brittle. Color, bright brass yellow, often tarnished in blue, purple and black hues. Before Blowpipe, Etc. — On charcoal fuses with scintillation to a brittle magnetic globule. With soda yields metallic malleable red button and sulphur test. In closed tube decrepitates, becomes dark and iridescent and may give deposit of sulphur. Flame and bead reaction like bornite.- Soluble in nitric acid with separation of sulphur, and from the solution ammonia throws down a brown precipitate, and leaves the liquid deep blue in color. Similar Species. — Chalcopyrite is softer and darker in color than pyrite, and differs from gold in black streak and brittleness. Remarks. — Chalcopyrite is probably formed in a manner similar to the formation of pyrite which is its frequent associate. Its most prominent associated minerals are the metallic sulphides and copper ores, many of which have been foimed by its alteration. It sometimes contains gold or silver. It is a very widely distributed mineral and the major part of all the copper produced is made from it. Prominent mines are in the Butte, ilontana, region ; and in Bingham Canyon, Utah. Also produced in large quantities, at Falun in Sweden ; Rio Tinto, Spain ; Sudbury, Canada ; and many other important localities. Uses. — It is the great ore of copper. Fig. 470. :^.- Missoula Co., Mont. ENARGITE. Composition. — CugAsS^, (Cu 48.3, As 19. i, S 32.6 per cent). Sometimes with Cu replaced in part by Zn or Fe and As by Sb. General Description. — A black brittle min- eral of metallic lustre, and occurring usually columnar or granular but sometimes in ortho- rhombic crystals. THE COPPER MINERALS. 269 Crystallization. — Orthorhombic. Axes a:b:c — o.%'j\ : i : 0.825. m = unit prism, /= 2d : b \ ^ c. Angles are 7!ini ='97" S3'; ^/= 59° S3'- Physical Characters. H., 3. Sp. gr, 4.43 to 4.45. Lustre, metallic. OpAQUE. Streak, blackish gray. Tenacity, brittle. Color, black or blackish gray. Before Blowpipe, Etc. — On charcoal fuses, yields white fumes with garlic odor. With soda yields malleable copper and a reaction for sulphur. In closed tube decrepitates, yields sulphur sublimate, then fuses and yields red sublimate of arsenic sulphide. Soluble in nitric acid. Remarks. — Enargite occurs with other copper minerals, especially arsenates derived from its alteration. It is found mainly in the mountains of Chili and Peru. Also at Butte, Montana, Gilpin county, Colorado; in South Carolina, Utah and California. Uses. — It is an ore of copper, and has been extensively mined. TENNANTITE. Composition. — CugAs^S,, grading into tetrahedrite by replacement of As by Sb. General Description. — A black metallic mineral best known in isometric crystals but occurring massive in the Utah mines. Physical Characters. — Opaque. Lustre, metallic. Color, black or very dark gray. Streak, dark reddish gray. H., 3.5 to 4. Sp. gr., 4.37 to 4.53. Before Blowpipe, Etc. — On coal fuses easily with intumescence and evolves white fumes with garlic odor. Frequently fuses to a magnetic globule due to the presence of iron. In closed tube decrepitates slightly. With soda yields malleable red button and sulphur reaction. Soluble in nitric acid. TETRAHEDRITE.— Gray Copper Ore. Composition. — CujSbjSj. Cu often partially replaced by Fe, Zn, Pb, Hg, Ag, and the Sb by As. General Description. — A fine grained, dark gray mineral of metallic lustre. Characterized especially by the tetrahedral habit of its crystals which are sometimes coated with yellow chalcopy- rite. Fig. 471. Fig. 472. Fig. 473. 270 DESCRIPTIVE MINERALOGY. Fig. 474. Fig. 475. Fig. 476. Crystallization. — Isometric. Hextetrahedral class p. 18. The tetrahedron p, Fig. 471, usually predominates, often modified by the tristetrahedron ?i ^ a : 2a : 2a, Figs. 474, 475, 476 and less frequently by other forms such as the dodecahedron d, Figs. 472, 476, and the tristetrahedron r = a : a : 2a, Fig. 473. Physical Characters. H., 3 to 4.5. Sp. gr., 4.5 to 5.1. Lustre, metallic. Opaque. Streak, black or reddish brown. Tenacity, brittle. Color, light steel to dark lead gray or iron black. Before Blowpipe, Etc. — On charcoal fuses easily to a globule 3vhich may be slightly magnetic. Evolves heavy white fumes with sometimes garlic odor. The roasted residue gives bead and flame reactions for copper. Soluble in nitric acid to a green solu- tion with white residue. Varieties — Varieties based upon the replacing metal as mercuric, argentiferous, platiniferous, bismuthiferous, etc., are given special names as Freibergite , Schwatzite, Rionite, etc. Similar Species. — The crystals are characteristic. The fine grained fracture in conjunction with the color is often sufficient to distinguish it. It is softer than arsenopyrite and the metallic cobalt ores, and does not generally yield a strongly magnetic residue on heating. Bournonite and chalcocite are softer, and finally the blowpipe reactions are distinctive. Remarks. — Occurs with the sulphides of lead, silver, copper, etc., especially in Humbolt County, Nevada, and numerous localities in Colorado. Also in Mexico, Bolivia, Chili, and in many parts of Europe. Uses. — It is sometimes worked for silver and also for copper. CUPRITE.— Red Oxide of Copper, Ruby Copper Ore. Composition. — Cu^O, (Cu 88.8 per cent.). Sometimes inter- mixed with limonite. THE COPPER MINERALS. 271 General Description. — Fine grained, masses dark red, brown- ish-red and earthy brick-red in color ; or deep red to crimson trans- parent isometric crystals usually octahedrons, or cubes. Also capillary. Fig. 477. Fig. 478. Fig. 479. Crystallization. — Isometric. Class of gyroid. The octahe- dron p, cube a and dodecahedron d predominating. Index of re- fraction for red light 2.849. Physical Characters. H., 3.5 to 4. Sp. gr., 5.85 to 6.15. Lustre, adamantine or dull. Transparent to opaque. Streak, brownish red. Tenacity, brittle. Color, crimson, scarlet, vermilion, or brownish red. Before Blowpipe, Etc. — On charcoal blackens and fuses easily to a malleable red button. Flame and bead tests give the color for copper. Soluble in nitric acid to a green solution. Soluble also in strong hydrochloric acid to a brown solution which diluted with water yields a white precipitate. Similar Species. — It is softer than hematite and harder than cinnabar or proustite, and differs from them all by yielding an emerald-green flame and a malleable red metal on heating. Remarks.— It is formed by oxidation of sulphides or the metal, and is found near the surface associated with limonite, quartz, and copper minerals. It changes to the black oxide and to the carbonates and silicate. In the United States it is especially abundant in the Arizona copper region. Also found in the Lake Superior region, and is abun- dant in Chili, Peru and Bolivia in association with the other copper ores. Uses. — It is an important ore of copper. TENORITE.— Melaconite, Black Oxide of Copper. Composition. — CuO, (Cu 79.85 per cent.). General Description. — Dull black earthy masses, black powder and shining black scales. Physical Characters. — Lustre, metallic in scales, dull in masses. Color and streak black. H., 3. Sp. gr., 5.82 to 6.25. Before Blowpipe, Etc. — Infusible, otherwise like cuprite. '■•J2 DESCRIPTIVE MINERALOGY. Remarks. — Occurs in fissures in the lava of Vesuvius, as & black coat on chalcopy- rite and as dull black masses with chrysocoUa. ATACAMITE. Composition.— Cu(0H)Cl-Cu(0H)2, (Cu 59.45, CI 16.64 per cent.). General Description.— Confused aggregates of crystals of bright or dark-green color. Also granular or compact massive, or as a crust. Rarely in slender orthorhom- bic prisms. Physical Characters. — Translucent to transparent. Lustre, adamantine to vit- reous. Color, bright green, emerald green, blackish green. Streak, apple green. H., 3 to 3.5. Sp, gr., 3.75 to 3,77. Before Blowpipe, Etc. — On charcoal, fuses to a copper red, malleable button, and colors the flame a beautiful and persistent blue without the aid of hydrochloric acid. In closed tube yields water and a gray sublimate. Soluble in acids to a green solution. CHALCANTHITE.— Blue Vitriol. Composition.— CuSO^'SHjO, (CuO 31.8, SO3 32.1, K^O 36.1 per cent.). General Description. — A blue, glassy mineral, with a disagreeable metallic taste. It occurs usually as an incrustation, with fibrous, stalactitic or botryoidal structure ; but sometimes in flat triclinic crystals. Physical Characters. — Translucent. Lustre, vitreous. Color, deep blue to sky blue. Streak, white. H., 2 5. Sp. gr., 2.12 to 2.30. Brittle. Taste, metallic nauseous. Fig, 480. K m Crystallization. — Triclinic. 0.551. Axial angles a = 82° 21'; pecially chalcopyrite. Axes a: b : c ^ 0.566 : I ; /? = 73° ll';r=77° 37/. Prominent forms, right and left unit prism m and M, unit pyra- mid /, and the pinacoids a and i5. Angles mM=z\iT,° 10'. Optically — . Before Blowpipe, Etc. — On charcoal, fuses, coloring flame green and leaving metallic copper. In closed tube yields water and sulphur dioxide and leaves a white powder. Easily soluble in water to a blue solution. Remarks. — It is produced by oxidation of the sulphides, es- Copper is sometimes saved by precipitation from mine waters containing chalcanthite. BROCHANTITE. Composition. — CuSO^ 3Cu(OH)2, (CuO 70.34, SO3 17.71 Hp 11.95 per cent.) General Description. — Velvety, emerald-green crusts of fine needle crystals and as botryoidal masses. Physical Characters. — Transparent to translucent. Lustre, vitreous. Color, emerald or blackish green. Streak, pale green. H., 3.5 to 4. Sp. gr., 3.9. Before Blowpipe, Etc. — On charcoal turns black, colors the flame emerald green and leaves malleable red button. Insoluble in water, but soluble in acids. In closed tube yields water, LIBETHENITE. Composition— Cu2( OH) PO4, (CuO 66.4, Vfi^ 29.8, H^O 3.8 per cent.). General Description. — A dark, olive-green mineral, usually in druses of short prismatic orthorhombic crystals and more rarely compact. THE COPPER MINERALS. 273 Physical Characters. — Translucent. Lustre, resinous. Color, olive green. Streak, olive green. H., 4. Sp.gr., 3.6103.8. Brittle. Before Blowpipe, Etc. — Fuses easily to a brown or reddish globule, coloring the flame emerald green, and yields metallic copper. Fused with lead yields a crystalline bead and metallic copper. In closed tube yields water and turns black. Soluble in nitric acid. OLIVENITE. Composition. — Cu2(OH)As04 (CuO 56.1, AS2O540.7, H.p 3.2 per cent.). General DescrIptio;^. — Needle-like orthorhombic crystals of dark olive-green, also nodules and fibrous or velvety masses of light-green to gray or brown color. Physical Characters. — ^Translucent to opaque. Lustre, adamantine to vitreous. Color, olive to blackish green, also yellow, brown, grayish white. Streak, olive green or brown. H., 3. Sp. gr., 4.1 to 4.4. Brittle. Before Blowpipe, Etc. — On charcoal, fuses, deflagrates, colors the flame bluish green and gives odor of garlic. Residue is a brown, brittle, somewhat crystalline but- ton. In closed tube, yields water. Soluble in nitric acid. MALACHITE.— Green Carbonate of Copper. Composition. — CUo(»OH)2C03, (CuO 71.9, CO^ 19.9, H^O 8.2 per cent.) /" General De.scription. — Bright-green masses and crusts, often with a delicate, silky fibrous structure or banded in lighter and darker shades of green. Sometimes stalactitic. Also in dull- green, earthy masses, and rarely in small, slender, monoclinic crystals. Frequently coating other copper minerals or filling their crevices and seams. Physical Characters. H., 3.5 to 4. Sp.. gr., 3.9 to 4.03. Lustre, silky, adamantine or dull. Translucent to opaque. Streak, pale green. Tenacity, brittle. Color, bright emerald to grass green or nearly black. Before Blowpipe, Etc. — On charcoal, decrepitates, blackens, fuses, and colors the flame green, leaving a globule of metallic copper. In closed tube, blackens and yields water and carbon dioxide. Soluble in acids, with effervescence. Similar Species. — Distinguished by color and effervescence with acids. Remarks. Malachite is formed by action of carbonated waters on other copper minerals. It is found chiefly with these or pseudomorphous after them, especially after cuprite and azurite. Immense deposits occur at Bisbee, Arizona, and other local- ities in the same region. Also in large deposits in Siberia, Chili and Australia. In smaller quantities it is found in the vicinity of all copper ores. Uses. — Is an ore of copper, and like marble is polished for or- namental articles, table-tops, etc. 274 DESCRIPTIVE MINERALOGY. AZURITE,— Blue Carbonate of Copper. Composition.— Cu3(OH)2(C03)2, (CuO 69.2, CO^ 25.6, Hp 5.2 per cent). General Description. — A dark-blue mineral occurring in highly modified glassy crystals and groups. When massive, it may be vitreous, sometimes velvety or dull and earthy. It fre- quently occurs as an incrustation on other copper ores, and dis- tributed through their cracks and crevices. Fig. 481. Fig. 482. \ ^\ »' I ^^ — ^v\ \ ,^ P . ^~^^\ a T ^ Arizona. Chessy, France. Crystallization. — Monoclinic. Axes a : b: ^=0.850 : i : 0.881; /3=87°36'. Crystals very varied in habit. Those figured show basal pina- coid c, ortho pinacoid a, unit prism m, unit dome o, and the pyra- mids /, r, and v. Prominent angles are mm= 99 " 1 9'; co = 135° 14'. Optically -f-. Physical Characters. H., 3.5 to 4. Sp. gr., 3.77 to 3.83. Lustre, vitreous. Translucent to opaque. Streak, blue. Tenacity, brittle. Color, dark blue to azure blue. Before Blowpipe, Etc. — As for malachite. Remarks. — Origin, associates and localities are the same as for malachite. Uses. — As an ore of copper and a rather unsatisfactory blue paint. CHRYSOCOLLA. Composition.— CuSiOj -|- 2H2O. Often very impure (CuO 45.2, SiOj 34.3, H2O 20,5 per cent.). General Description. — Green to blue incrustations and seams often opal-like in texture, or sometimes, from impurities, resem- bling a kaolin colored by copper. Also brown, resembling limonite, and in dull green earthy masses. Never found in crystals. THE COPPER MINERALS. 27s Physical Characters. H., 2 to 4. Sp. gr., 2 to 2.3. Lustre, vitreous, dull. Translucent to opaque. Streak, white. Tenacity, brittle. Color, green to light blue, brown when ferriferous. Before Blowpipe. Etc. — In forceps or on charcoal is infusible, but turns black, then brown and colors the flame emerald green. In bead, reacts for copper. With soda, yields malleable copper. In closed tube, yields water. Decomposed by hydrochloric acid, leaving a residue of silica. Boiled with KOH, yields a blue solu- tion, from which excess of NH4CI precipitates flocculent HjSiOj. Similar Species. — It is softer than turquois or opal and does not effervesce like malachite. Remarks. — ChrysocoIIa occurs with other copper minerals, especially near the tpps of veins. It is probably formed by the action of hot solutions of alkaline silicates on other copper ores. Found at Clifton, Arizona; Hartville, Wyoming, and in most of the prominent copper-bearing regions. Uses. — As an ore of copper and an imitation turquois. DIOPTASE. Fig. 483. Composition.— HjCuSiO^, (CuO 50.4, SiOj 38.2, Y{f> 11.4 per cent.). General Description. — Glassy, emerald-green crystals and druses of indistinct crystals. Also found massive. Crystallization. — Hexagonal, c' = 0.534. R i\ R^^ 125° 55'- 2 A 2 ^ 95° 26^'. Commonly prismatic, with rhombo- hedral terminations. Physical Characters. Transparent to opaque. Lustre, vitreous Color, emerald green. Streak, green. H , 5. Sp. gr., 3.28 to 3.35. Brittle. Cleavage, rhombohedral. Before Blowpipe, Etc. — Decrepitates, blackens, colors the flame emerald green, but is infusible. In closed tube, blackens and yields water. Gelatinizes with acids. CHAPTER XXVIII. MERCURY AND SILVER MINERALS. THE MERCURY MINERALS. The minerals described are : Metal, Mercury ; Sulphide, Cin- nabar ; Chloride, Calomel. The only ore is cinnabar with which the native metal sometimes occurs in small quantities. The ore is usually low grade, that mined in this country yielding an average of less than one per cent, of mercury. The world's product of mercuiy in 1898 was about 4,600 tons, of which the United States produced about one-fourth, or 1,163 tons. In 1899 the output of the United States was 1,095 tons.* Mercury is obtained from cinnabar by heating the larger lumps in a shaft-furnace, resembling a continuous lime kiln, with three exterior fire places. A little fuel is also mixed with the ore. The heat decomposes the sulphide, forming fumes of sulphur dioxide and mercury. These fumes are carried off through large iron pipes to condensers where the mercury is liquified. The finer ore is heated in a vertical shaft containing a series of inclined shelves down which the ore slips whenever any is drawn off at the bottom. The fumes go to the condensers already mentioned. Mercury is extensively used in certain processes for the extrac- tion of gold and silver from their ores and in the manufacture of vermilion. Minor uses are in barometers, thermometers, silvering mirrors, and in medicine. MERCURY. Composition. — Hg, with sometimes a little silver. General Description. — A tin white liquid with metallic lustre. Usually found in little globules scattered in the gangue, or in cavities with cinnabar or calomel. Physical Characters. — Opaque liquid. Lustre, metallic. Color, tin white. .Sp. gr., I3-59- Before Blowpipe, Etc. — Entirely volatile. In matrass or closed tube may be collected in small globules. Soluble in nitric acid. * Engineering and Mining Journal, 1900, p. 2. MERCURY AND SILVER MINERALS. 277 CINNABAR,— Natural Vermilion. Composition. — HgS, (Hg 86.2 per cent.). General Description. — Very heavy, bright vermilion to brown^ ish red masses of granular texture ; more rarely small transparent rhombohedral crystals, or bright scarlet powder, or earthy red mass. Sometimes nearly black from organic matter. Physical Characters. H., 2 to 2.5. Sp. gr., 8 to 8.2. LusTREj adamantine to dull. Opaque to transparent. Streak, scarlet. Tenacity, brittle to sectile. Color, cochineal red, scarlet, reddish brown, blackish. Before Blowpipe, Etc. — Completely volatilized without fusion if pure. With soda gives sulphur reaction. In closed tube yields black sublimate, which becomes red when rubbed ; if soda is used a metallic mirror is obtained instead of the black sublimate, and by rubbing with a splinter of wood globules of mercury may be collected. If cinnabar powder is moistened with hydrochloric acid and rubbed on bright copper the coin is coated with mercury. Soluble in aqua regia. Similar Species. — Cinnabar is softer and heavier than hematite, cuprite, and rutile. It has more decided red streak than crocoite and realgar, and differs from proustite in density and blowpipe reactions. Remarks. — Cinnabar occurs in slate rocks and shales, and sometimes in granite or porphyry associated with sulphides of iron, copper, antimony, and arsenic, and with native gold. Its chief localities are Idria, Southern Austria; Almaden, Spain ; Huan- cavelica, Peru ; Kwei-chan, China ; Ekaterinoslav, Russia, and at several places in Lake, San Benito, Napa, and Santa Clara counties, California Uses. — It is the only important ore of mercury. The artificial cinnabar is the important pigment vermilion. CALOMEL— Horn Mercury. Composition. — Hg2Cl2, (Hg 84.9 per cent.). General Description. — A gray or brown translucent mineral of the consistency of horn. Usually found as a coating in cavities with or near cinnabar. Sometimes in well-developed tetragonal forms = 142" 16' ; rr = 157° 29' ; cp = 139° 42' ; cr= 157° i'- Optically — , with low refraction and weak double refraction. Physical Characters. H., 4.5 to 5. Sp. gr., 3.17 to 3.23. Lustre, vitreous to resinous. Transparent to opaque. Streak, white. Tenacity, brittle. Color, green, red, brown, yellow, violet, white, colorless. Cleavage, imperfect basal and prismatic. Before Blowpipe, Etc. — Fuses with difficulty on sharp edges and colors the flame yellowish-red, or, if moistened with concen- trated sulphuric acid, colors the flame momentarily bluish-green. Easily soluble in hydrochloric acid. If to ammonium molybdate in nitric acid solution a few drops of a nitric acid solution of apatite be added, a bright-yellow pre- cipitate will be thrown down on heating. In the chlorine variety silver nitrate will produce a curdy white precipitate in the nitric acid solution. Varieties. — Certain mineral deposits are essentially of the same composition as crystalline apatite. Phosphorite. — Concretionary masses, with fibrous or scaly struc- ture. H = 4.5. Osteolite. — Compact, earthy, impure material, of white or gray color. H., I to 2. Phosphate Rock or Nodules. — The former in place of original deposition, the latter chiefly in river beds. Massive, gray, white, brown or black. H., 2 to 5. Guano. — Granular to sponge-like and compact material, of gray to brown color. Sometimes with lamellar structure. Similar Species. — Green crystals, differ from beryl in lustre, hardness and solubility. Red crystals differ from willemite in not gelatinizing or yielding zinc. Remarks. — Occurs in granites, limestones, tin veins, beds of iron ore, etc., fre- quently as inclusions in other minerals, and is of both igneous and secondary origin. The most productive American localities for the pure mineral are in Ontario and Quebec, Canada; Ottavifa County, Quebec, having several productive mines. Other deposits, but smaller in extent, occur at Bolton, Mass.; Crown I'oint, N. Y., and Hurdstown, N. J. Immense deposits of the phosphate rock, so largely used in fer- 3IO DESCRIPTIVE MINERALOGY. tilizers, occur in eastern South Carolina and in Florida ; in the latter case underlying a wide belt of country and extending through several counties in the central part of the State. Uses. — The massive varieties and some crystalline deposits fur- nish most of the phosphates for fertilizers. It is converted into soluble phosphates by treatment with sulphuric acid, in which state it is available as plant food. Apatite is also used in the manufacture of phosphorus. PHARMACOLITE. Composition. — CaHAsOj.aH^O, (CaO 25.9, AsjOj 53.3, H.p 20.8 per cent.). General Description. — White or pink silky fibres or powder, and rarely small monoclinic crystals. Physical Characters. — Translucent to opaque. Lustre, silky, dull. Color, white or tinged red by erythrite. Streak, white. H., 2 to 2.5, Sp. gr., 2.64 to 2.73. Before Blowpipe, Etc. — Fuses to a white or bluish enamel and colors the flame light blue. On charcoal, yields garlic odor. In closed tube, yields water. Easily soluble in acids. Remarks. — Occurs with arsenical ores, especially smaltite, arsenopyrite and proustite. ARAGONITE.— Flos Ferri. Composition. — CaCOj, (CaO 56.0, CO2 44.0 per cent.). General Description. — This form of calcium carbonate is found in orthorhombic crystals, which are frequently pseudo- hexagonal from twinning, and as groups of acutely terminated needle crystals, which grade into fine fibres. It also occurs stal- actitic, incrusting and in pure white groups of interlacing, coral- like stems. The prevailing tint is white, but is occasionally violet or pale green. Fig. 522. Fig. 523. Fig. 524. Fig. 525. Bilin, Boh. Herrengrund. Crystallization. — Orthorhombic. Axes a-.b -.c = 0.622 : i : 0.721. Occasionally simple crystals. Fig. 522, with acute domes CALCIUM AND MAGNESIUM MINERALS. 311 and pyramids such as e = ao a-.b -.60 and Fig- S26. s = ^a:~b:6c. These grade into needle-Hke forms, Fig. 526. More frequently twinned, with twin plane m, giving prisms with pseudo- hexagonal cross sections, Fig. 524 and 525. Angles are: mm = 116° 12'; dd = 108° 27'; vv = 49" 39'. Optically — . Axial plane a. Acute bi- sectrix normal to c. Axial angle for yellow light, 2E = 30° 54'. Cumberland. Physical Characters. H., 3.5 to 4. Sp. gr., 2.93 to 2.95. Lustre, vitreous. Translucent or transparent. Streak, white. Tenacity, brittle. Color, white, violet, yellow, pale green. Cleavage. — Parallel to brachy pinacoid, prism, and brachy dome. Before Blowpipe, Etc. — Infusible, colors flame red. In closed tube decrepitates, loses weight and falls to pieces. With hydro- chloric acid, dissolves with rapid effervescence. Similar Species. — Needle crystals differ from those of natro- lite in the terminations. Strontianite and witherite have higher specific gravity and are fusible. Calcite differs in form and cleaves in three directions with equal ease yielding diedral angles of 105° 5', whereas aragonite cleaves: i. Easily parallel to the brachy pinacoid, yielding plates. 2. Indistinctly parallel to prism, yielding angle of 116° 12'. 3. Very indistinctly parallel to a brachy dome. Remarks. — Aragonite is largely deposited from carbonated water solution princi- pally in rock cavities and mineral veins. It is found with gypsum and in beds of serpentine and with iron ores as flos ferri, the coraloidal variety. It can be changed into calcite by heat, and the difference between it and calcite is supposed to be that the calcite is deposited from cold solution and aragonite from hot solution. It is not of common occurrence, but is found at Sulphur Creek and Colton, California, also in Solano County, Cal. ; in Lockport and Edenville, N. Y. ; in Madi- son CouAty, N. Y. ; Haddam, Ct. . Warsaw, 111., etc. CALCITE. — Calcspar, Limestone, Marble, Iceland Spar, Etc. Composition. — CaCOj, (CaO 56.0, CO2 44.0 per cent). General Description. — Yellowish white to white or colorless, more or less transparent crystals, usually rhombohedrons or sca- lenohedrons. Massive with easy cleavage or coarse to fine- 312 DESCRIPTIVE MINERALOGY. grained, stalactitic, and occasionally fibrous, lamellar or pulveru- lent. Fig. 527. Fig. 528. Fig. 529. Fig. 530. Fig. 531. Fig. 533. K3^^ --^ Dog Tooth Spar, Geikie. Fig. 534. Fig. S3&. Fig. 537. Fig. 538. Fig. 532. Fig. 535. Fig. 539. Crystallization. — Hexagonal. Scalenohedral class, p. 39. Axis c = 0.854. CALCIUM AND MAGNESIUM MINERALS. 313 Occurs in several hundred forms, of which the most common are the rhombohedra : p, the unit ; f = « : 00 « : a : ^-c ; /= a : 00 a : a:2c;q^=a:coa:a: \6c ; the scalenohedron : v = ^a : ■^a-.a-.y, and the unit prism. Twins are frequent by several laws, see p. 68. Important angles are pp = 105° 5'; ee = 134° 57'; ff= 78° 51'; qq = 60° 36'. The polar edges vv are 104° 38' and 144° 24'. Optically — . With very strong double refraction, but weak re- fraction (a = 1.486 ; ?- = 1.658 for yellow light). Physical Characters. H., 3. Sp. gr., 2.71 to 2.72. Lustre, vitreous to dull. Transparent to opaque. Streak, white. Tenacity, brittle. Color, yellow, white, colorless, or pale shades of red, green, blue, etc. Cleavage, parallel to the rhombohedron, therefore yielding di- edral angles of 105° 5' and 74° 55'. Before Blowpipe, Etc. — Infusible. Becomes opaque and alka- line and colors flame red. Soluble readily in cold dilute acids, with vigorous effervescence. Varieties. — The following are the most prominent varieties : Iceland Spar. — Colorless, transparent crystals and masses. Dog Tooth Spar. — Scalenohedral crystals, supposed to resemble canine teeth in shape. Fontainebleau Sandstone. — Crystals containing up to 60 per cent, of sand. Satin Spar. — Fibrous, with silky lustre. Argentine. — Foliated, pearly masses. Marble. — Coarse to fine granular masses, crystalline. Limestone. — Dull, compact material, not composed of crystalline grains. Chalk. — Soft, dull-white, earthy masses. Calcareous Marl. — Soft, earthy and intermixed with clay. Stalactites. — Icicle-like cylinders and cones, formed by partial evaporation of dripping water. Stalagmite. — The material forming under the drip on the floor of the cavern. Travertine, Onyx. — Deposits from springs or rivers, in banded layers. Other names, such as Hydraulic Limestone, Lithographic Lime- 314 DESCRIPTIVE MINERALOGY. stone. Rock Meal, Plumbocalcite, Spartaite, etc., are of minor im- portance, and are chiefly based on color, use, locality, etc., and do not generally indicate important structural or chemical dif- ferences. Similar Species. — The distinctions from aragonite have been given under that mineral. Dolomite differs in slow partial solu- tion in cold dilute acids, instead of rapid and complete efferves- cence. Remarks. — Calcite is very widely distributed. It is derived, in great part, from fossil remains, shells, corals, etc, but also, in considerable part, by the decomposition of calcium silicates by hot carbonated waters, and possibly, in a degree, by the action of heat on aragonite. The carbonated waters deposit aragonite or calcite, according to the temperature of the solution. In the production of marble Vermont is far ahead of any other State, and the centre of the industry is situated at Rutland. Georgia and Tennessee also produce large quantities, especially of a beautiful, coarse, granu- lar structure. Alabama, California, New York, Pennsylvania and Massachusetts also have large deposits, some of which are worked. Crystallized calcite occurs through- out the world in all limestone regions. In the Unjted States these localities are innu- merable and transparent varieties are common. Rossie, N. Y. ; Warsaw, 111., and Llano and Lampasas Counties, Texas, may be especially noteworthy. Fine stalactites occur in the caves of Virginia, Kentucky and New York. Deposits from thermal springs are common in the Yellowstone Park, and similar deposits occurring in San Luis Obispo County, California, are cut and polished, yielding slabs of onyx marble of extreme beauty. Uses. — Limestone and marble are important building stones, and the latter is also used for .statuary, ornaments, interior work, tombstones, etc. Limestone, again, is used for making quicklime and as a flux in smelting siliceous ore, in glass-making, in many chemical processes, in hydraulic cement, as a lithographic stone etc. Iceland spar is used in optical apparatus for polarizing light. DOLOMITE,— Pearl Spar, Magnesian Limestone. Composition. — (Ca.Mg)C03 often contains iron or manganese. General Description. — Small, white, pink or yellow, rhombo- hedral crystals, usually with curved faces, or more frequently white, massive marble, with coarse to fine grain ; or gray, white and bluish, compact limestone. Crystallization. — Hexagonal, class of third order rhombohe- dron, p. 46. Axis c= 0.832. Usually the unit rhombohedron /, Fig. 540. Sometimes the more acute rhombohedron r = a: aa a : a: \c. Important angles are pp = 106° 15'; rr = 66°, 7'. Optically — , with even stronger double refraction than calcite. CALCIUM AND MAGNESIUM MINERALS. 315 Fig. 540. Fig. 541. Fig. 542. Joplin, Mo. Physical Characters. H., 3.5 to 4. Sp. gr., 2.8 to 2.9. Lustre, vitreous or pearly. Translucent to opaque. Streak, white. Tenacity, brittle. Color, white, pink, greenish-gray, brown or black. Cleavage. Rhombohedral. Angles, 106° 15' and 73" 45', Before Blowpipe, Etc. — Infusible, colors flame yellowish -red and becomes alkaline. With cobalt solution, becomes pink. Fragments are very slightly attacked by cold dilute acid. The powdered mineral is sometimes attacked vigorously by cold dilute acid, but sometimes is not. On heating there is a vigorous effer- vescence. Similar Species. — Differs from calcite in effervescence, color with cobalt solution and frequent curvature of rhombohedral planes. It differs from siderite and ankerite in not becoming magnetic on heating. Remarks. — Dolomite is frequently the chief constituent of whole mountain ranges and may have formed: i. From a solution of the mixed carbonates of calcium and magnesium in carbonated waters. 2. From calcite by infiltration of waters contain- ing magnesium carbonate. 3. By solution of part of calcium carbonate of a mag- nesian limestone in preference to the less soluble magnesium carbonate, thus increas- ing the proportion of the latter. Many of the marbles of Vermont, Georgia and Tennessee contain magnesium, and frequently enough to be classed under dolomite. Crystals are common in many localities, especially in the zinc region of Missouri, in many places in the limestone region of Western New York, in the gorge at Niagara, at Glen Falls and Brewsters, N. Y., at Stony Point, N. C. ; Roxbury, Vt., and else- where. Uses. — The same as for calcite. The dolomite limestone and marble are less soluble than the calcite varieties, and are to that extent, preferable for construction. It is also used for making epsom salts. 3i6 DESCRIPTIVE MINERALOGY. ANKERITE. Composition. — (Ca.Mg.Fe)C03 sometimes containing manganese. General Description. — Gray to brown rhomboUedral crystals like those of siderite, also cleavable and granular masses and compact. Physical Characters. — Translucent to opaque. Lustre, vitreous to pearly. Color, gray, yellow or brown. Streak, white or nearly so. H„ 3.5 to 4. Sp. gr., 2.95 to 3.1. Brittle. Cleavage, rhombohedral. R f\ R^\oiP \2' . Before Blowpipe, Etc. — Infusible, darkens and becomes magnetic. Soluble in acids with effervescence. SCHEELITE. Composition. — CaWO^, (CaO 19.4, WO3 80.6 per cent), some- times with replacement by molybdenum. General Description. — Heavy brownish white or white masses and square pyramids. Also drusy crusts of yellow or brown crystals. Fig. 543. Fig. 544. Fig. 545. Schlackenwald . Trumbull, Conn. Crystallization. — Tetragonal. Class of third order pyramid, p. 29. Axis c = 1.536. The unit first order pyramid / and second order d are most common with sometimes a modifying third order pyramid, x = a: 3 « : 3 c. Angles ^x& pp = 100° 5' ; ee = 107° 20'. Optically +. Physical Characters. H., 4.5 to 5. Sp. gr., 5.4 to 6.1. Lustre, adamantine. Transparent to opaque. Streak, white. Tenacity, brittle. Color, pale yellow, gray, brown, white or green. Cleavage, distinct parallel to first order pyramid, indistinct parallel to second order pyramid. Before Blowpipe, Etc. — Fusible with difficulty on sharp edges. In salt of phosphorus forms a clear bead which in the reducing CALCIUM AND MAGNESIUM MINERALS. 317 flame becomes deep blue, and if the bead is powdered and dis- solved in dilute hydrochloric acid it yields a deep blue solution, especially on addition of metallic tin. Scheelite is soluble in hy- drochloric or nitric acid, leaving a yellow residue. Similar Species. — Distinguished among non-metallic minerals by its weight and behavior in salt of phosphorus. Remarks. — Scheelite occurs in crystalline rocks, and usually with cassiterite, wolf- ramite, topaz, fluorite, molybdenite, and in quartz. It changes into wolframite, and also forms from wolframite. The mineral is by no means common, but is found at Monroe and Trumbull, Conn. ; Flowe mine, S. C, in Nevada, Idaho, and Colorado. Also in large crystals at Marlow, Quebec. Uses. — Scheelite is used as a source of tungsten, which has im- portant properties when used in the manufacture of ferro-tungsten and tungsten steel. Other applications are in the manufacture of tungstic acid, from which a yellow pigment is obtained, and tungs- tate of soda, which renders fabrics almost incombustible. PEROVSKITE. Composition. — CaTiOj. General Description. — Light yellow to black cubic crystals and kidney-shaped masses. Also as a rock constituent in microscopic octahedral crystals. Physical Characters. — Color, yellow, brown and black. Lustre, adamantine. Streak, grayish. Brittle. H., 5.5. Sp.gr., 4.1. Transparent to opaque. Before Blowpipe, Etc. — Infusible. Gives titanium reactions in S. Ph. Decom- posed by hot sulphuric acid. Insoluble in hydrochloric acid. Remarks. — Found in serpentine at Syracuse, N. Y. , in chlorite slate at Achma- tovsk Urals and in talcose schist in Zermatt, Tyrol. THE MAGNESIUM MINERALS. The minerals described are : Hydroxide, Bkucite ; Sulphate, Epsomite ; Carbonate, Magnesite ; Aluminate, Spinel. Magnesia is also the principal base in several important silicates and occurs in many others, and in the carbonate dolomite. The carbonate, magnesite, is not rare, over 30,000 tons being produced annually and the hydroxide and sulphate also occur in considerable quantities. Magnesite is used as a lining for the converters m the basic pro- cesses for steel, and for other purposes where a very refractory material is desired. It is the favorite source of carbon dioxide in seltzer and soda water manufacture, as the treatment with sulphuric acid leaves a soluble residue of crude epsom salts which can be re- covered. It is also used in the manufacture of certain kinds of wood-pulp paper. 3i8 DESCRIPTIVE MINERALOGY. The metal magnesium prepared by the electrolysis of the double chloride of potassium and magnesium, and purified by distillation out of contact with air, is now made in some quantity in the shape of ribbon and as coarse grains. It is used in flash lights to pror duce a vivid light for photographing in absence of sunlight, as a reducing agent in the preparation of some of the rarer elements, as a purifying agent to remove the last traces of oxygen from copper, nickel and steel and as a dehydrating agent for certain oils and for alcohol. The metal is steadily increasing in commercial impor- tance. BRUCITE. Composition. — Mg(OH)2, (MgO 69.0, HjO 31.0 per cent). General Description. — White or gray translucent foliated masses with pearly or wax-like lustre. Also fibrous and in tabular hexagonal crystals. Physical Characters. H., 2.5. Sp. gr., 2.38 to 2.4. Lustre, pearly or wax-like. Translucent. Streak, white. Tenacity, sectile and flexible. Color, white, bluish, greenish. Cleavage, basal. Before Blowpipe, Etc. — Infusible, becomes alkaline, and with cobalt solution becomes pink. Yields water in closed tube. Solu- ble in hydrochloric acid. Similar Species. — Harder and more soluble than foliated talc or gypsum, and quite infusible. Remarks.— Brucite is usually found in serpentine or limestone with magnesite or hydromagnesite. On exposure it becomes coated with a white powder, and is some.- times changed to serpentine or hydromagnesite. Its most prominent American locality is at Texas, Pa., also at Fritz Island in the. same State; at Brewsters, N. Y. and Hoboken, N. J. ' " '' EPSOMITE.— Epsom Salt. CoMPOSiTiON.-MgSO,-f- 7 HjO, (MgO 16.3, SO332.5, Hp 51.2 per cent.). General Description.— A delicate white fibrous efflorescence Yiq. 546. or earthy white crust with a characteristic bitter taste. Also com- 1 mon in solution in mineral water. Occasionally in needle crystals, f\ 1 ? \ which are especially noticeable as representing the sphenoidal class ^""^^ ^ of symmetry in the orthorhombic system. Optically. — , Physical Characters. — Transparent or translucent. Lustre, vitreous or dull. Color and streak, white. H., 2 to 2.5. Sp.gr., 1.75. Taste, bitter and salt. Before Blowpipe, Etc.— Fuses at first, but beomes infusible after the water of crystallization has been driven- off. With co- Hj^ CALCIUM AND MAGNESIUM MINERALS. 319 bait solution becomes pink. In closed tube yields acid water. Easily soluble in water. Remarks. — Epsomite is formed by action of the sulphuric acid of decomposing sulphides, upon such magnesian minerals as serpentine and magnesite. MAGNESITE, Composition.— MgCO,, (MgO 47.6, CO^ 52.4 per cent), with sometimes iron or manganese replacing part of the magnesium. General Description.— White chalk-like lumps and veins in serpentine. Rarely fibrous or in rhombohedral crystals closely agreeing with dolomite in form and angle. ^ = 0.811. R hR — 107° 24'. Physical Characters. H., 3.5 to 4.5. Sp. gr., 3 to 3.12. Lustre, dull, vitreous or silky. Opaque to translucent. Streak, white. Tenacity, brittle. Color, white, yellow, brown. Fracture, conchoidal. Before Blowpipe, Etc. — Infusible, becomes alkaline. With cobalt solution becomes pink. Soluble with effervescence in warm hydrochloric acid, but does not effervesce in cold dilute acid. No decided precipitate is produced by addition of sulphuric acid, whereas heavy precipitates form with solutions of calcite and dolomite. Similar Species. — Differs from dolomite and calcite in not yielding the calcium flame. Remarks, — Usually formed with serpentine by action of carbonated waters on eruptive magnesian rocks, such as olivine (chrysolite), or when the decomposition is carried further the results are magnesite and quartz. As the former is the more common decomposition, magnesite usually occurs with serpentine and also with other magnesian minerals, such as talc, brucite, dolomite, etc. Found at Bolton and Sutton, Province of Quebec, at Texas, Pa., Barehill, Md., and at several localities in California and Massachusetts. Uses. — It is used in the lining of converters in the basic process for steel, and for lining kilns in the manufacture of sulphuric acid and for other purposes where a non-conducting and refractory material is required. It also is used in obtaining carbon dioxide for soda water, the residue being converted into epsom salts. Epsom salts, magnesia, and magnesia alba are also made from magnesite. SPINEL.— Balas Ruby. Composition.— Mg(A102)2, (MgO 28.2, Al^Og 71.8 per cent.). Iron, manganese and chromium are sometimes found. 320 DESCRIPTIVE MINERALOGY. General Description. — Usually in octahedral crystals, simple or twinned, which cannot be scratched by steel or quartz and vary in color according to composition. Also in rolled pebbles and loose crystals. Crystallization. — Isometric, the octahedron p or this modi- fied by the dodecahedron d or the trisoctahedron o — a: ■i,a: 3«. Index of refraction with yellow hght 1.7 15 5. Fig. 547. Fig. 548. Fig. 549. Physical Characters. H., 8. Sp. gr., 3.5 to 4.5. Lustre, vitreous. Transparent to opaque. Streak, white. Tenacity, brittle. Color, red, green, blue, black, brown, yellow. Cleavage, octahedral. Before Blowpipe, Etc. — Infusible, often changing color, the red variety becomes green, then nearly colorless, finally red. In powder is turned blue by cobalt solution. Insoluble in hydro- chloric or nitric acid, but somewhat soluble in sulphuric acid. Varieties. — Balas Ruby or Ruby Spinel (Magnesia Spinel). — Clear red or reddish, often transparent. Sp. gr., 3.5 to 3.6. Ceylonite (Iron Magnesia Spinel). — Dark-green, brown, black, usually opaque. Picotite (Chrome Spinel). — Yellowish to greenish-brown, trans- lucent. Similar Species. — Characterized by octahedral crystals and by hardness. Remarks. — Occurs in limestone, serpentine, gneiss, etc., associated with corundum, chondrodite, brucite, etc , and sometimes changed to talc, muscovite or serpentine. Gem specimens have been obtained at Hamburg, N. J.; San Luis Obispo, Cal., and Orange County, N. Y. The crystals also occur in many localities in North Carolina, Massachusetts and near the New York and New Jersey line. Especially abundant in Ceylon and Burmah. Uses. — Transparent varieties are used as gems. CHAPTER XXXIII. ALUMINUM MINERALS. The minerals described are : Fbwride, Cryolite ; Oxides and Hydroxides, Corundum, Bauxite, Diaspore, Gibbsite ; Sulphates, Alunogen, Aluminite, Alunite. Phosphates, Turquois, Wavel- LiTE, Lazulite. Aluminum is also present in many silicates. The minerals of aluminum, aside from the clays, have important commercial applications, which may be roughly classified as : I. Ores of Aluminum. II. Abrasive materials. III. Gems. Ores of Aluminum. Metallic aluminum, formerly prepared only by reduction of the chloride by the metal sodium, is now made in relatively large quantities by electrolysis. In 1 899 there was produced in this country 3,250* tons of the metal, which sold as low as 28 cents per pound. Only bauxite and gibbsite are at present used as ores, bauxite being preferred on account of cheapness, as gibbsite is not found in quantity, whereas about 36,000 tons of bauxite were mined in the U. S. in 1899. Corundum is too difficult to obtain and has too high a value as abrasive material, and the abundant clays and silicates contain a much smaller percentage of aluminum, and be- fore using, need to be decomposed and freed from silica. The ore is heated with sodium carbonate to low redness, in order to produce sodium aluminate without rendering the silica or iron soluble. On dissolving out the sodium aluminate with water and passing carbon dioxide through the solution, aluminum hydroxide is formed, which yields the oxide when heated. By this mode of procedure most of the iron and sihcon is separated, which would otherwise be reduced by the current and alloyed with the aluminum. For the production of the pure metal the oxide is decomposed by electrolysis in a fused solvent which protects the metal from * Engineering and Mining Journal, 1900, p. 2. 322 DESCRIPTIVE MINERALOGY. contact with oxygen. The Hall process consists in the electroly- sis of the oxide in a fused bath of cryolite or the mixed fluorides of sodium and aluminum. The process is carried on in iron tanks, the bottom and sides of which are thickly lined with carbon. The tanks serve as the negative electrodes and are filled with the cryolite flux, to which a little fluorite is added. The positive elec- trodes are carbon cylinders, which dip into the electrolyte. The cylinders are first lowered until they touch the bottom of the tank, and the ground cryolite is melted as a result of the poor contact. The cylinders are then raised, and the current thenceforth passes through the melted liquid. The alumina is now added, and is immediately dissolved by the flux and decomposed by the current. The metal settles at the bottom of the bath, while the oxygen combines with the carbon of the anode and escapes as carbon dioxide. The metal is removed from time to time, alum- ina is again added and thus the operation is continuous. The aluminum thus produced is a white metal, with a bluish tint — a good conductor of heat and electricity, malleable and duc- tile and not easily tarnished. It is used in the manufacture of ' scientific apparatus where lightness, strength and non-corrosive- ness are desirable, also, to a small extent, in making cooking utensils ; and in Germany, for making army equipments and shells for cartridges. It has a considerable use in the manufacture of fancy articles and in ornamental work, and in steel, copper and zinc castings a fraction of i per cent, of aluminum is added to the melted metal to prevent blow-holes. The powdered metal is used in the shape of a bronze powder and, in the form of aluminum leaf and paint, it is also used for silvering letters and signs. The use of aluminum in sheet form is steadily increasing and is replacing sheet copper and zinc to some extent. It is also assuming impor- tance as an electrical conductor. About 500 tons were used in sheet form and 650 tons for electrical conductors in 1898.* Aluminum is especially sonorous and is now used in the Austrian army for drums, and the substitution of aluminum for brass in the other band instruments is being tried. The alloys of aluminum are extensively used especially the alloy with copper, known as aluminum bronze, which contains usually as much as ten per cent, of aluminum. It is extremely tough and is extensively applied in machinery, especially mine machinery, "^ Engineering and Mining Journal, 1899', p. 8. ALUMINUM MINERALS. 323 engine castings, etc. Tlie alloys with zinc, nickel and tin are also of importance and to some extent are replacing brass. Cryolite to the amount of about 10,000 tons per year is im- ported into the United States from Greenland, its only important locality, and is used in making sodium carbonate, alum and calcium fluoride. A small amount of cryolite is used as a flux in the manufacture of aluminum as above described. Bauxite to the amount of 35,842 long tons was mined in Georgia and Alabama in 1899,* these two States having the only known American deposits of importance. This ore is the source of most of the aluminum of commerce and is also used in the production of alum and other compounds of aluminum used extensively in dyeing and calico printing. The output of the mineral is steadily increasing. Abrasive Materials. Corundum to the amount of about 250 tons per year is mined in the South, and a somewhat larger amount of emery is imported for use in grinding and polishing. The production of corundum is rapidly decreasing owing to the artificial production in quantity of an extremely hard carbide of silicon, known as carborundum, which is supplanting it as an abrasive. Gems. Rubies and sapphires, which are varieties of corundum, turquois and chrysoberyl are all found of sufficient beauty to be classed as gems or precious stones. In this country sapphires have been found in Montana, but their status in the gem market is not yet very well defined. A considerable amount of turquois of a mark- etable grade has been mined in New Mexico and new deposits are reported in Nevada. CRYOLITE.— Eisstein, Composition. — AlNagF^. (Al 12.8, Na 32.8, F 54.4 per cent.). General Description. — Soft, translucent, snow-white to color- less masses, resembling spermaceti or white wax in appearance. Occasionally with groups of triclinic crystals so slightly inclined as to closely approach cubes and cubic octahedrons in angle and form. * Engineering and Mining Journal, 1900, p. 2. 324 DESCRIPTIVE MINERALOGY. Physical Characters. H., 2.5. Sp. gr., 2.95 to 3. Lustre, vitreous or wax-like. Translucent or transparent. Streak, white. Tenacity, brittle. Color. — Colorless, white, brown. Cleavage. — Basal and prismatic, angles near 90°. Before Blowpipe, Etc. — Fuses very easily, with strong yellow coloration of the flame, to a clear globule, opaque when cold. With cobalt solution, becomes deep blue. In closed tube, yields acrid fumes, which attack and etch the glass. Soluble in acid without effervescence. Similar Species. — Characterized by its easy fusibility, and fumes which attack glass. Remarks. — Found at Ivigtut, Greenland, as a large bed in a granite vein, and con- tains, scattered through it, crystals of siderite, quartz, chalcopyrite and galenite. This is the only locality where cryolite is produced in commercial quantities, but here the supply seems inexhaustible. Small amounts have been found at Miask, Urals, and in the United States at Pike's Peak, Colorado. Uses. — It is used in the manufacture of sodium carbonate, and aluminum hydroxide, and is made into alum. The by-product, cal- cium fluoride, is sold to smelters and glass manufacturers. Cryo- lite is also used as a flux or bath in the manufacture of aluminum. CORUNDUM.— Sapphire, .Ruby, Emery. Composition. — AI2O3, (Al 52.9, O 47.1 per cent.). General Description. — With the exception of the diamond, the hardest of all minerals. Occurs in three great varieties, which are most conveniently described separately. Sapphire or Ruby. — Transparent to translucent, sometimes in crystals and of fine colors — blues, reds, greens, yellows, etc. Adamantine Spar or Corundum. — Coarse crystals or masses, with nearly rectangular cleavage, or granular, slightly translucent, and usually in some blue, gray, brown or black color. Emery. — Opaque, granular corundum, intimately mixed with hematite or magnetite, usually dark-gray or black in color. Crystallization. — Hexagonal. Scalenohedral class, p. 40. Axis f= 1.363. Crystals often rough and rounded. Second order pyramids predominate as n, o, and zu intersecting the vertical axis at respectively |-c, ^c and 2c. Unit rhombohedron/ and the more acute form / {2c) also occur. Angles nn = 128° 2' ; 00 = 122° 22'; ww= 124°- ALUMINUM MINERALS. 32S Fig. 550. Fig. 551. Fig. 552. Optically — , with rather strong refraction but weak double refrac- tion (a= 1.759; r= '■7<57)- Physical Characters. H., 9. Sp. gr., 3.95 to 4. 11. Lustre, vitreous or adamantine. Transparent to opaque. Streak, white. Tenacity, brittle to tough. Color, blue, red, green, yellow, black, brown or white. Cleavage, rhombohedral, angle of 86° 4'. Before Blowpipe, Etc. — Infusible and unaltered, alone or with soda, or sometimes improved in color. Becomes blue with cobalt solution at high heat. Insoluble in acids and only slowly soluble in borax or salt of phosphorus. Remarks. — Occurs in granular limestone, granite, gneiss and other crystalline rocks and in the gravel of river-beds. It is usually associated with chloritic minerals, rarely with quartz, and is frequently found altered, and many alteration products occur, as spinel, feldspar, mica, tourmaline, cyanite, fibrolite, etc. The American localities producing corundum or emery are : Raburn County, Ga. ; Macon, Clay and Jackson Counties, N. C. ; Westchester County, N. Y. ; Chester County, Pa., and Chester, Mass. Fair-sized rubies and sapphires have been obtained near Helena, Montana, and at several localities in North Carolina. The finest rubies are obtained from Upper Burmah and Ceylon. Uses. — Sapphire and ruby, when clear and transparent, are valuable gems, the ruby sometimes being more highly valued than the same weight of diamond. The various colors have dif- ferent names ; Blue, sapphire ; red, ruby ; yellow, oriental topaz ; green, oriental emerald ; purple, oriental amethyst. Adamantine spar and emery are the most important abrasive materials, and thousands of tons are used in grinding and polishing. Corundum can be used in the electric smelting processes for aluminum, but its price makes this unprofitable. 326 DESCRIPTIVE MINERALOGY. BAUXITE. Composition. — K\0{ with or without the cube a and dodecahedron d. Strongly pyroelectric. Fig. 557. Fig. 558. V Physical Characters — Transparent to opaque. Lustre, vitreous. Color, white, yellowish, greenish. Streak, white. H., 7 (crystals), 4.5 (masses). Sp. gr., 2.9 to 3. Brittle. Before Blowpipe, Etc. — Fuses easily with intumescence, to a white glass and colors the flame yellowish green. In closed tube yields no water or but little. Solu- ble slowly in hydrochloric acid. Remarks. — Occurs in deposits of halite, gypsum, anhydrite, and especially in the immense beds of potassium and magnesium salts at Stassfurt, Prussia. BORON, SULPHUR, CARBON, ETC. MINERALS. 335 THE SULPHUR AND TELLURIUM MINERALS. The minerals described are : Sulphur and Tellurium ; the prin- cipal sulphur minerals, however, are the sulphides and sulphates elsewhere described. According to the estimate of W. H. Adams,* the United States consumed a total of 316,303 long tons of sulphur in 1897. Of this amount 137,725 tons was in the form of brimstone, almost wholly imported from Sicily, and 1 78, 578 tons was present in pyrite from which it was burned. About two-thirds of the pyrite was imported and mainly from the Rio Tinto mines of Spain. Sulphur is also recovered in large quantities from the former waste products of gas works, Leblanc soda factories and other chemical works. Considerable quantities are also burned off from the sulphides of zinc and copper during the recovery of the metals and in a few localities, notably in Germany, the sulphur dioxide fumes are util- ized in the manufacture of sulphuric acid. Nine-tenths of the world's supply of native sulphur is obtained from the Island of Sicily. In this country 1,337 lo^g tons were produced in 1899.! Sulphur is extracted from the native mineral by simple fusion and consequent separation from the gangue. The common method in use in Sicily involves the burning of part of the sulphur to melt the remainder, causing heavy loss of the element. The crude sul- phur may be refined by sublimation. Pyrite is burned directly in specially constructed furnaces, the sulphur dioxide produced being used almost solely in the manufacture of sulphuric acid. Tellurium is included in this section on account of its close chemical relation to sulphur. It has no commercial importance. SULPHUR.— Brimstone. Composition. — S, sometimes with traces of tellurium, selenium, or arsenic. Often mixed with clay or bitumen. General Description. — Yellow, resinous, orthorhombic pyra- mids, usually translucent or transparent ; also in crusts, stalactites, spherical shapes, and powder. Color usually pale-yellow to sul- phur-yellow, but is sometimes brown or green. * Mineral Industry, 1898, p. 562. \ Engineering and Mining Journal, 1900, p. 2. 336 DESCRIPTIVE MINERALOGY. Fig. 559. Fig. 560. Crystallization. — Orthorhombic. Axes a: b: c= 0.813 : i : 1.903. Usually the pyramid/, sometimes modified by the base c, the pyramid s ^ a : b : y^ c, or the dome d= co a: b : c. Angles //= 106° 26; .fJ-= 126° 51'; cd= 117° 43'. Optically +. Axial plane, the brachy pi nacoid. Acute bisectrix vertical. Axial angle with yellow light 2 V= 69° 5'. Physical Characters. H., 1.5 to 2.5. Sp. gr., 2.05 to 2.09. Lustre, resinous. Transparent to translucent. Streak, white or pale yellow. Tenacity, brittle. Color, yellow, yellowish-orange, brown or gray. Cleavage, parallel to base, prism and pyramid, not perfect. Before Blowpipe, Etc.— Melts easily, then takes fire and burns with a blue flame and suffocating odor of sulphur dioxide. In closed tube melts and yields a fusible sublimate, brown hot, yellow cold, and if rubbed on a moistened silver coin the coin is blackened. Insoluble in acids. Remarks. — Formed in large deposits by the decomposition of sulphides, or of sul- phates, especially gypsum, which by water and decaying organic matter are reduced to the sulphide with subsequent production of hydrogen sulphide which on decomposition forms sulphur. Sulphur is also deposited from hot springs. The great sulphur producing region of the world is the island of Sicily. Deposits are numerous in the United States, and have been developed at Cove Creek and Fresno, Utah ; and Winnemucca, Nevada. Extensive deposits are also known in California, Louisiana, Wyoming and Texas. Less important occurrences are numerous. Uses. — Sulphur is used in immense quantities for the manufacture of sulphuric acid, gunpowder, matches, rubber goods bleaching, medicines, etc. Large quantities of it, however, are recovered in various chemical and metallurgical operations as by-products. BORON, SULPHUR, CARBON, ETC. MINERALS. 337 TELLURIUM. Composition. — Te with a little Se, S, Au, Ag, etc. General Description. — A soft tin white mineral of metallic lustre occurring fine grained or in minute hexagonal-prisms. Physical Characters. — Opaque. Lustre, metallic. Color and streak, tin-white. H., 2 to 2.5. Sp. gr., 6.1 to 6.3. Rather brittle. Before Blowpipe, Etc. — On charcoal fuses easily, volatilizes, coloring flame green and forming a white coat, which is made rose color by transferring to porcelain and moistening with sulphuric acid. Soluble in hydrochloric acid. THE HYDROGEN MINERALS. Hydrogen is a constituent of many minerals being present in combination and as water of crystallization. It is present to a limited extent in natural gas and in volcanic gases, it escapes in combination with sulphur from many sulphur springs and in com- bination with carbon occurs as marsh gas, petroleum, ozocerite, etc. It has been of the utmost importance in mineral formation and alteration and for that reason is considered here. Its compound WATER is properly included as a mineral. WATER.— Ice, Snow. Composition. — H^O (H., 11. i, O., 88.9 per cent). General Description. — Ice or snozu at or below 0° C. Water from 0° to 100° C. Steam above 100° C, or aqueous vapor at all ordinary temperatures. Crystallization. — Hexagonal. Axis c = 1.403 approximately. As snow, the crystals are principally compound star-like forms branching at 60" and of great diversity. Simple crystals are some- times found as hail. Optically -|- FiG. 561. Fig. 562. Fig. 563. Fig. 564.. Magnified Snow Crystals. Physical Characters. H. (ice), 1.5, Sp. gr. (ice), 0.91. Lustre, vitreous. Transparent. Streak, colorless. Tenacity, brittle. Color, white or colorless, pale blue in thick layers. Tasteless if pure. 338 DESCRIPTIVE MINERALOGY. Before Blowpipe, Etc. — Melts at o° C. Under pressure of 760 mm. boils at 100° C. and is converted into steam. Remarks. — Rarely pure, usually containing air, carbon dioxide, some of the salts of calcium, magnesium, sodium, potassium, etc., and even traces of the metals. When pure it is tasteless and a universal solvent. THE CARBON MINERALS. The definite minerals described are : Diamond and Graphite. In addition to these Coal, Asphaltum, Petroleum, Ozocerite and Amber are economically important carbon compounds which are on the border line of mineralogy, being without definite com- position or crystalline form. Carbon also exists in all organic matter, in all carbonates ; in the carbon dioxide of the air ; and in natural gas. Diamonds have been found in this country, but practically, the production for the world is from the South African mines, with a limited amount from New South Wales and from Brazil. Nearly three million carats were mined in Kimberley, South Africa, in 1897.* Graphite is mined in New York, Pennsylvania, and Rhode Island and to a limited extent in a few other States. In 1898 the output of the mines in this country was 1900 tons.f The total product of the world is over 50,000 tons annually, obtained mainly from Austria and Ceylon. The uses of graphite are numerous, the best known being, pencils, crucibles, stove polish, lubricants, paints for iron and foundry facings. Mineral coal, excluding peat and lignite which retain the woody structure, is compact massive material produced by a gradual alteration of organic deposits chiefly vegetable. Bituminous, or soft coal, which retains a large amount of volatile matter readily con- verted by heat into gases was mined to the extent of 158,955,931 tons in this country in 1898. J Anthracite, or hard coal, which contains little volatile matter was produced during the same year§ to the amount of 49,947,571 tons. About one-half of our total output of coal is mined in Pennsylvania. The United States now produces about one-third of the coal of the world. * Mineral Industry, 1898. ^Engineering and Mining Journal, 1899, p. 3. ^Engineering and Mining Journal, 1899, p. 3. llbid. BORON, SULPHUR, CARBON, ETC. MINERALS. 339 AsPHALTUM or mineral pitch is a mixture of different hydro- carbons, brown to black in color and grading between liquid and solid. Different names, such as elaterite, gilsonite, and albertite, have been given to varieties from different localities. The chief locality for asphaltum is the famous pitch lake of the ' island of Trinidad, although deposits of asphaltic sandstone are mined in California, Utah, Kentucky, and other States in this country, and asphaltic limestones are mined in France and Switz- erland. Nearly 200,000 tons were used in the United States in 1897, of which about two-thirds were imported. The principal use is for street pavements, usually mixed with 70 to 80 per cent, of sharp sand, 5 to 1 5 per cent, of limestone, and a little coal-tar residium. It is also used as cement, roofing, and floor material, and for coating wood or metal to prevent decay or rust. Asphaltum is also a constituent of some varnishes. Petroleum is closely related to asphaltum, and may be regarded as including the liquid members of the series. In 1897 the wells of this country yielded 56,985,643 barrels* of the crude oil, which was converted into naphtha, illuminating oils, lubricating oils and paraffine. It is obtained also in Canada, Russia, India and Burma. Ozocerite or mineral wax is essentially a paraffin, colorless to white when pure, but oftener greenish or brown, and possessing all the properties of beeswax except its stickiness. It is found in Galicia, Hungary, and Utah, and is extensively used. In the crude state it serves as an insulator for electric wires. By dis- tilling it yields a refined product, ceresine, used for candles, waxed paper and hydrofluoric acid bottles ; burning oils ; parafiine ; a product with properties and appearance of vaseline ; and a black residiuum which in combination with India rubber constitutes the insulating material called okonite. In 1897 over 7000 tons were mined in Hungary. Amber or succinite is a fossil resin found chiefly along the Prussian coast of the Baltic Sea. It is usually transparent and of a yellowish or brownish color. Its chief use is for jewelry and for mouth pieces for pipes. * Mineral Industries, 1898. 340 DESCRIPTIVE MINERALOGY. DIAMOND. Composition. — C. General Description. — Transparent, rounded, isometric crys- tals with a peculiar adamantine lustre like oiled glass. Usually colorless or yellow, and with easy octahedral cleavage. Also translucent, rough, rounded crystalline aggregates and opaque crystalline or compact masses of gray to black color and no dis- tinct cleavage. Especially characterized by a hardness exceed- ing that of any other known substance. Fig. 565. De Beer's Mine, Kimberley, S. A. Crystallization. — Isometric. Hextetrahedral class, p. 18. Octahedra, often showing inverted triangular depressions, see Fig. 565, and hextetrahedral modifying faces, are most common while rounded hexoctahedra and more rarely cubes and other forms occur. Frequently twinned parallel to the octahedron. Index of refraction for yellow light 2.4195. Physical Characters. H., 10. Sp. gr., 3.15 to 3.52. Lustre, adamantine. Transparent to opaque. Streak, colorless. Tenacity, brittle. CoLORj colorless, yellow, rose, green, blue, gray, black. Cleavage, octahedral. Before Blowpipe, Etc. — Is slowly consumed, producing its equivalent of carbon dioxide. In powder it is burned by ordinary blowpipe flame. Insoluble in acids. BORON, SULPHUR, CARBON, ETC. MINERALS. 341 Yk.B.i'ETi'ES.-^ Carbonado or Black Diamond. — Opaque, dark-col- ored, and without cleavage. Sp. gr., 3.15 to 3.29. Bort. — Translucent, non-cleavable, crystalline aggregates, often harder than the crystals and more tough. Sp. gr., 3.499 to 3.503. The name bort is also applied to fragments of crystals. Remarks. — Origin not known. The diamond is found in alluvial deposits with other minerals, such as gold, platinum, zircon. The great South African localities, however, while in part alluvial or "river diggings," are chiefly confined to a limited area where they occur enclosed in a wall of carbonaceous shale surrounding a ser- pentine shale core, in which are found not only the diamonds, but garnets, zircon magnetite, etc. Diamonds have also been found in quartzose conglomerates and with the so-called flexible sandstone "itacolumite." Although diamonds have been found in isolated localities in the southern and west- ern States no deposits, not even of an alluvial character, have been discovered in North America. By far the largest diamond deposit ever found occurs at Kimberley, South Africa, and immense quantities are mined here annually. Alluvial deposits which have become famous occur in Brazil, India, the Urals and Borneo. Uses. — As a gem when transparent and without flaw ; colorless stones and those of decided tints ranking superior to yellow or brownish stones. Smaller stones, especially the translucent and opaque crystals, are used in cutting machinery, diamond drills, saws, etc., on account of their great abrasive power. The dust is also used in polishing other diamonds. GRAPHITE.— Plumbago, Black Lead. Composition. — C. Sometimes with iron, sand, clay, etc. General Description. — Disseminated flakes or scaly to com- pact masses, and more rarely six-sided plates. Soft, greasy and cold to the touch ; black to very dark gray in color and usually metallic in lustre. When impure it is apt to be slaty or earthy. Physical Characters. H., i to 2. Sp. gr., 2.09 to 2.25. Lustre, metallic to dull. Opaque. Streak, dark-gray. Tenacity, scales flexible. Color, black or dark gray. slightly sectile. Cleavage, basal, cleaves into plates. Unctuous, marks paper. Before Blowpipe, Etc. — Infusible, but is gradually burned. May react, if impure, for water, iron and sulphur. Insoluble in acids. If a piece of graphite is brought into contact with a piece of zinc in a solution of copper sulphate, it is quickly copper-plated. Molybdenite under the same test is very slowly plated. 342 DESCRIPTIVE MINERALOGY. Similar Species. — Differs from molybdenite in darker color, streak, flame test and salt of phosphorus bead, and as above men- tioned. Micaceous hematite is harder and has a red streak. Remarks. — Graphite probably results from alteration of embedded organic matter coal, peat, etc., by heat, destructive distillation and pressure. It occurs disseminated in crystalline limestones and granites and in larger irregular masses. Large deposits exist in Ceylon, Austria and Eastern Siberia. Almost all the American output is obtained at Ticonderoga, N. Y. Deposits at Southampton, Pa., and near Raleigh, N. C, have also produced graphite in commercial quantities. Uses. — Graphite is used for refractory vessels, as crucibles, re- torts, stove polish, etc., for lead pencils, in electroplating, in elec- trical supplies, in casting moulds, as a finish, as a lubricant for machinery, as a paint for iron, etc., for coating metals, shot, gun- powder, etc. CHAPTER XXXV. SILICA AND THE SILICATES. The minerals composed of silica alone and the silicates cannot conveniently be classified upon an economic basis, and we have, therefore, followed practically the order of Dana's " System of Min- eralogy," Sixth Edition, believing that — in this country, at least — most collections of minerals will be arranged in this order for many years. The order herein followed is : A. — Silica. B. — Anhydrous Silicates: I. Disilicates and Polysilicates. II. Metasilicates. III. Orthosilicates. IV. Subsilicates. C. — Hydrous Silicates : I. Zeolite Division. 11. Mica Division. III. Serpentine and Talc Division. IV. Kaolin Division. D. — TiTANO Silicates. ECONOMIC DISCUSSION. Aside from the occasional occurrence of certain silicates in spec- imens suitable for gems, only a few of this greatest group of common minerals are of economic importance as distinct minerals. The great stone or quarry industry,* however, which represents in the United States a capital of nearly ;^ 100,000,000, and produced in 1889 material worth in the rough over ;^50,ooo,ooo, consists in the extraction of blocks of either carbonate of lime or magjiesia or of silica and silicates. For instance, in 1889 the values of materials quarried in this country were : * The facts and figures, where given for the year 1889, are essentially those of the Eleventh Census Report on Mineral Industries, pp. 595 to 666. The figures for 1897 are taken from Mineral Industry, 1 898. 344 DESCRIPTIVE MINERALOGY. Granite, $14,464,095 Sandstone, 10,816,057 Bluestone, 1,689,606 Slate 3,482,513 The amount of stone used in building in this country in 1897 was approximately of the value of ^30,000,000. Granite, commercially speaking, includes a number of hard, durable rocks, such as granite proper, syenite, gneiss, basalt, dio- rite, and andesite, which are composed of silicates — usually three or more — and principally quartz, the feldspars and the micas, pyroxene and amphibole. It is used in enormous quantities in buildings, in paving blocks and in construction of bridges and dams. In 1889, 62,287,156 cubic feet were quarried in the United States, of which 26,000,000 were used in building and 20,000,000 in paving blocks. Sandstone is composed of grains, chiefly quartz, with sometimes a little feldspar, mica or other minerals, and classified as siliceous ferruginous, calcareous or argillaceous, according to the nature of the cement which binds the grains together. Its uses are the same as those of granite, but a larger proportion of the quantity quar- ried is used in building. In 1889, 71,571,054 cubic feet were quarried in the United States. Bluestone is a very hard, durable, fine-grained sandstone, ce- mented together with siliceous material. It is used principally for flag and curb stone. In 1889, 5,126,340 cubic feet were quarried in the United States. Slate is used chiefly as roofing material and for interior work, such as blackboards, table tops, sinks, etc. Slate and slate manu- factures to the amount of ^3,243,220 were produced in the United States in 1897. Fibrous talc and compact talc, or soapstone, are extensively used, the former for grinding to "mineral pulp," used in paper manufacture, the latter for, many purposes, usually because it is refractory, expands and contracts very little, retains heat well and is not attacked by acids. These properties make it valuable in furnaces, crucibles, sinks, baths, hearths, electrical switch boards and cooking utensils. Talc is also used in cosmetics, refractory paints, slate pencils, crayons, gas tips, as a lubricant and in soap making. In 1897 there were produced in this country 58,836 tons of fibrous talc and 18,974 tons of soapstone. SILICA AND THE SILICATES 345 The micas, mjascovite, phlogopite and biotite, have become of great importance as non-conductors in electrical apparatus, and are also used in stove and furnace doors. The larger sheets are cut and split to the desired size ; the waste is, to some extent, built up into plates suitable for certain grades of electrical work, and for covering steam boilers and pipes. Large amounts of former waste material are now ground and used for decorative interior work, to ornament porcelain and glassware, to spangle wall paper, in calico printing, as a lubricant and more recently as an absorbent of nitro glycerine and in the manufacture of certain smokeless powders. Sheet mica to the amount of 92,335 pounds was pro- duced in this country in 1897 and 2,692 tons of scrap mica were ground. AsBESTUS. — The minerals amphibole and serpentine, in their fibrous varieties, are known commercially as asbestos, and are ex- tensively used as incombustible paper, cloth, cement, boiler and steam-pipe covering, yarn or rope for packing valves. Only 900 tons were obtained in 1898 in the United States. The large supply coming from Canada and Italy is the fibrous serpentine, chrys- otile. Serpentine is, to some extent, mined and used as an ornamen- tal stone, but is commercially classed with the marbles. Feldspar is crushed in large quantities for admixture with kaolin in the manufacture of porcelain. In the United States 20,900 tons were produced in 1898. Quartz is also used in large amounts in the manufacture of sand -paper, porcelain, glass, in honestones, oilstones, and as a flux. Its colored and chalcedonic varieties are used as precious or ornamental stones. In 1897 the United States produced 750,000 long tons of quartz and quartz sand. Infusorial earth is calcined and made into water filters, pol- ishing powders, soap filling and boiler and steam-pipe covering. Kaolinite and Clay. — Enormous and varied industries use as their raw material the beds of clay which result from the decom- position of the feldspars and other silicates. These beds are com- posed in part of some hydrous aluminum silicate such as kaoHnite, but usually with intermixed quartz, mica, undecomposed feldspar, oxides and sulphides of iron. Their properties and uses depend chiefly upon their composition. Clay products to the amount of ^56,121,101 were manufactured in 1897 in the United States. 346 DESCRIPTIVE MINERALOGY. The industries include the manufacture of common brick, paving brick, fire-brick, and hydraulic cement, all varieties of earthenware, stoneware and porcelain, terra cotta, sewer pipes and drain tiles, and are carried on all over the country and the world. Fullers earth, a special form of clay, was mined in Florida to the extent of 17,049 tons in 1897. It is used largely in the refin- ing and clarifying of oils. The minerals beryl, garnet, topaz, tourmaline, spodumene, titanite and chrysolite are sometimes found in specimens which are valuable as gems. SILICA. The minerals composed of silica (SiOj) are Quartz, Tridymite and Opal. QUARTZ.— Agate, Jasper, Chalcedony. Composition. — SiO^ (Si 46.7, O 53.3 per cent). General Description. — A hard, brittle mineral which may oc- cur as more or less transparent, vitreous masses or as hexagonal crystals, and of all colors, but especially colorless, milky, white, amethyst, smoky and red. Also found in cavities, particularly as translucent, non-crj'stalline layers of gray, yellowish and bluish tints and with usually a mammiUary, stalactitic or nodular struct- ure. Also found as more or less opaque, non-crystallized material Fig. 566. Fig. 567. Fig. 568. containing considerable amounts of iron, and alumina, and often highly colored, as red, brown, or yellow. In rocks quartz rarely has definite shape, but apparently forms last and fills the interstices between the other minerals. Crystallization. — Hexagonal. Class of trigonal trapezohe- dron, p. 44. Axis c= 1.0999. Usually a combination of unit SILICA AND THE SILICATES. 347 prism m with one or both rhombohedra, p and/, the former gen- erally larger and brighter, and the prism faces nearly always horizontally striated. The second order pyramid s= 2a: 2a: a -.20 Fig. 569. FiQ. 570. Fig. 571. Fig. 572. frequently occurs and rarely the trapezohedral faces ;tr= -|« : 6a: a : 6c either right, Fig. 571, or left, Fig. 572. Angles // = 94° 14'; mp = 141" 47'; ms = 142" 2'; mx = 167° 59'. Fig- 573- Fig. 574. Fig. 575. Kai, Japan, Twinned crystals are not rare. Fig. 573 shows two crystals with twinning plane the second order prism. Fig. S74. is an inter- growth of a right-handed. Fig. 571, and a left-handed crystal, Fig. 572. Fig. 575 shows twin plane a:2a:2a:c,m which the vertical axes cross almost at right angles. Optically +. With low refraction and weak double refraction («= 1.544; r= I-S53 foi" yellow light). Circularly polarizing. Basal sections i mm. thickness turning plane of polarization for yellow light 21.7° to right or left. 348 DESCRIPTIVE MINERALOGY. Physical Characters. H., 7. Sp. Gr., 2.6 to 2.66. Lustre, vitreous to greasy. Transparent to opaque. Streak, white. Tenacity, brittle to tough. Color, colorless and all colors. Cleavage, difficult, parallel to rhombohedron. Before Blowpipe, Etc. — Infusible. With soda, fuses with marked effervescence to a clear or opaque bead, according to the proportions used. Insoluble in salt of phosphorus and slowly soluble in borax. Insoluble in all acids except hydrofluoric. Varieties. A. Crystalline Varieties. — Vitreous in lustre, often transpa- rent ; occurring in isolated or grouped crystals or drusy surfaces or crystalline. Rock Crystal. — Pure, colorless or nearly colorless quartz. Amethyst. — Purple to violet and shading to white. Fracture shows lines like those of the palm of the hand. Color disappears on heating, and is probably due to a little manganese. Rose Quartz. — Light-pink or rose-red, becoming paler on long exposure to light. Usually massive. Colored by titanium or manganese. Yellow Quartz or False Topaz. — Light yellow. Smoky Quartz. — Dark yellow to black. Smoky tint, due to some carbon compound. Milky Quartz or Greasy Quartz. — Translucent. Usually mass- ive. Common as a rock constituent. Ferruginous Quartz. — Opaque, brown or red crystals, sometimes small and cemented like a sandstone. » Aventurine. — Spangled with scales of mica, hematite, or goethite. Cats Eye. — Opalescent, grayish-brown or green quartz with in- cluded parallel fibres of asbestus. B. Chalcedonic Varieties. — With lustre like wax. Translu- cent. Not in crystals. Frequently nodular, mammillary, stalac- titic or filling cavities. Chalcedony. — Pale blue or gray varieties, uniform in tint. Agate. — Strata or bands representing successive periods of depo- sition, and frequently of different tints or with irregularly mingled colors or visible colored inclusions constituting such sub-varieties as banded agate, clouded agate, moss agate, ruin or fortification agate, etc. SILICA AND THE SILICATES. 34 Carnelian or Sard. — Blood-red or brownish-red. Onyx and Sardonyx. — Parallel layers of lighter and darker color, as white and black, white and red, etc. The layers are in planes. 67«ryj(7/rrti'^.j— Apple-green. Prase. — Dull leek-green. Plasma, Heliotrope and Bloodstone. Bright to dark-green, spotted with white or red dots. C. Jasper Varieties. — Opaque, dull in lustre, usually high in color, impure from clay and iron. Fig. 576. Fig. 577. Hot Springs, Ark. Fig. 578. Herkimer, Co., N. Y. Fig. 579. Qialcedony, Antwerp, N. V. Agate. Schlottwitz, Saxony. D. In ADDITION TO THESE, there are Flint. — Smoky-gray to nearly black, translucent nodules, found in chalk-beds. Touchstone. — Velvet-black and opaque, on which metal streaks are easily made and compared. Sandstones. — Quartz grains cemented by silica, iron oxide, clay, calcium carbonate, etc. Quartzite, compact quartz, granular or slaty in structure. 3SO DESCRIPTIVE MINERALOGY. Remarks.— Quartz is chiefly found as an original constituent of such rocks as granite, gneiss, etc , formed by igneous or plutonic action, and also, to a very large extent, 'as a deposit from solution in water. Silicates are attacked by carbonated waters', forming carbonates of calcium, magnesium, sodium, etc., and leaving a resi- due of silica. This, in turn, is soluble in hot solutions of these same carbonates, and is dissolved, transported, and, by evaporation and cooling, is redeposited, filling seams, cavities, veins, etc. Quartz is the most common of all solid minerals, and occurs with almost all other species and in almost all localities. Uses. — Aside from the uses of the quartz rocks in building, etc., large quantities of quartz are used in the manufacture of sand- paper, glass, porcelain and as an acid flux in smelting. The chal- cedonic varieties — agate, onyx, etc. — are often polished and used as ornaments, and so also are some of the jaspers. Rock crystal is used in cheap jewelry, and is cut for spectacles and for some forms of optical apparatus. The colored crystalline varieties are often cut in cheap jewelry, and the amethyst, when of a particular dark purple, is highly valued as a gem. TRIDYMITE. Composition. — SiOj. General Description. — Small colorless, six sided plates. Often in wedge-shaped groups of three (trillings), which are sometimes octahedral in appearance. Physical Characters. — Transparent. Lustre, vitreous. Color, colorless or white. Streak, white. H., 7. Sp. gr., 2.28 to 2.33. Brittle. Before Blowpipe, Etc. — Like quartz, but soluble in boiling sodium carbonate. Remarks. — Occurs in cavities in volcanic rocks, such as trachyte or andesyte. OPAL. Composition. — SiOj.i^HgO, (HjO, 5 to 12 percent.). General Description. — Transparent to translucent veins and masses, usually of milky-white or red color and frequently show- ing blue, green, red, etc., internal reflections (opalescence). This grades into less translucent and opaque masses, with no play of color and somewhat resembling chalcedony, but without the wax- like lustre. Other varieties are transparent, like melted glass, and opaque and earthy. Physical Characters. H., 5.5 to 6.5. Sp. gr., 2.1 to 2.2. Lustre, vitreous, pearly, dull. Transparent to opaque. Streak, white. Tenacity, brittle. Color, colorless and all colors. Before Blowpipe, Etc. — Infusible. Becomes opaque and yields more or less water. Soluble in hydrofluoric acid more easily than quartz and soluble in caustic alkalies. SILICA AND THE SILICATES. 35 1 Varieties. Preciojis Opal. — Milky-blue, yellow or white translucent material with fine internal reflections, attributed to thin curved lamellae, which have been cracked, bent and broken during solidification. Fire Opal. — Reddish or brown in color and with reflections hav- ing the appe^.'rance of fire. Common or Semi-Opal. — Translucent to opaque, with greasy lustre and of all colors, but without opalescence. Most frequently yellow or brown. Wood Opal. — Petrified wood, the petrifying material being opal. Opal Jasper. — Like ordinary jasper, but with resinous lustre. Hyalite. — Colorless transparent masses resembling drops of melted glass or of gum arable. Geyserite, Siliceous Sinter. — Loose, porous rock of opal silica deposited from hot water. Opaque, brittle and often in stalactitic or other imitative shapes. Fiorite or Pearl Sinter. — Pearly, translucent material found in volcanic tufa and near hot springs. Tripolite or Infusorial Earth. — Massive, chalk-like or clay- like material composed of the remains of diatoms. Similar Species. — Softer than quartz and soluble in caustic alkalies. May also yield noticeable water in a closed tube. Rarely confused with any other mineral. Remarks. — Occurs in fissures in igneous rocks or imbedded in limestone, clay- beds, etc. Fine precious opals are found at Gem City, Washington ; at Opaline, Idaho ; also in Latah County, Idaho, and Morrow County, Washington. Queretaro and Zimapan, Mexico, also yield good gems. Other famous localities are Czerwe- nitza, Hungary; Bula Creek, Queensland, and Wilcannia, New South Wales. De- posits of infusorial earth occur at Dunkirk, Md. ; Richmond, Va. ; Virginia City, Mo., also in Connecticut, New Hampshire, New Jersey and California. All of these deposits have been worked, but not continuously. Uses. — Precious and fire opals are beautiful gems. Opalized wood is cut and polished for ornament. Tripolite has many uses ; e.g., polishing and washing powders, lagging for boilers, cement, soluble glass, and as the dope in dynamite. POLYSILICATES. The POLYSILICATES may be derivatives of HjSijOj, H^SijO^, H^SijOj, and possibly other more complicated silicic acids, or they may be formed by isomorphic mixtures of salts of these 352 DESCRIPTIVE MINERALOGY. acids with each other or with the orthosilicates or metasilicates. Many of the polysilicates are so variable and so complex that it is impossible to express their composition by formula, and many others are designated by formulse which are, at the best, but ap- proximations. Under this head comes Petalite, a derivative of HjSijOj, and the important subdivision of the Feldspars, deriva- tives of H^SijOg and of fairly definite composition. PETALITE. Composition. — LiA^Si^Ojjj. General Description.— Glassy white or gray foliated and cleavable masses and rarely minute, colorless crystals, like pyroxene in form. Physical Characters. — Transparent to translucent. Lustre, vitreous. Color, colorless, white, gray, occasionally pink. Streak, white. H.; 6 to 6.5. Sp. gr., 2.39^ to 2.46. Before Blowpipe, Etc. — Phosphoresces with gentle heat ; with strong heat, whitens and fuses on the edges and colors the flame carmine. Insoluble in acids. THE FELDSPARS. These are of great importance as rock-forming minerals and have a close resemblance in many characters ; e.g. : Very similar in crystalline form. System either monoclinic or triclinic. Prism angles nearly 120°; many of the other angles closely agreeing. Two prominent cleavages inclined at or near 90°. Hardness, 6 to 6.5. Specific gravity, generally between 2.55 and 2.75. Composition, R'AlSijOg or R^'AI^SijOg, or isomorphic mixtures of these. The feldspars here described are Orthoclase, Microcline,. Albite, Oligoclase, Labradorite, Anorthite. ORTHOCLASE.— Feldspar, Potash Feldspar. Composition. — KAlSijOg, with some replacement by Na. General Description. — Cleavable masses, showing angle of 90; and monoclinic crystals, of flesh-red, yellow or white color. Also compact, non-cleavable masses, resembling jasper or flint. Some- times colorless grains or crystals. Crystallization. — Monoclinic. Axes /5 = 63" 57' ; a:~b : c = 0.659 : I : 0.555. Most frequent forms : unit prism m, pina- coids i> and c and positive orthodomes o = a : o:> 6 : c and j = a : CO d: 2c. Angles are: mm= 118° 47'; cm= 112° 13'; co= 129° 43 >^'; 0'=99° 42'. SILICA AND THE SILICATES. 353 Twin forms of Carlsbad type Fig. 584 (twinning plane the ortho pinacoid) very common ; the Baveno type Fig. 585 (^twinning plane a clino dome) and Mannebacher type (twininng plane the base c), Fig. 586, less common. Fig. 580. Fig. 584. Fig. 581. Fig. 582. Fig. 585. Fig. 583. 1 / 1/ X— - Fig. 586. Optically —, with weak refraction and double refraction. Axial plane usually normal to b. In thin sections rarely shows multi- ple twinning and is frequently turbid from kaolin. Physical Characters. H., 6 to 6.5. Sp. gr. 2.44 to 2.62. Lustre, vitreous or pearly. Transparent to opaque. Streak, white Tenacity, brittle. Color, flesh-red, yellowish, white, colorless, gray, green. Cleavage, parallel to c and b, hence at right angles. Before Blowpipe, Etc. — Fuses in thin splinters to a semi-trans- parent glass and colors flame violet. Insoluble in acids. Varieties. Ordinary. — Simple or twinned crystals of nearly opaque pale red, pale yellow, white or green color. More frequently cleavable massive as in granitic rocks. 354 DESCRIPTIVE MINERALOGY. Adularia. — Colorless to white, transparent, often opalescent. Usually in crystals. Sanidine and Rhyacolile. — Glassy, white or colorless crystals in lava, trachyte, etc. Loxoclase. — Grayish-white or yellowish crystals, which have a tendency to cleave parallel to the ortho pinacoid. Felsite. — Jaspery or flint-like masses of red or brown color. Similar Species. — Differs from the other feldspars in the cleav- age at 90°, the greater difficulty of fusion, the absence of stria- tions, etc. Remarks —Usually of igneous origin, sometimes secondary. With mica and quartz it forms the important rocks granite, gneiss, and mica schist, and is also the basis of syenite, trachyte, porphyry, etc. It changes to kaolin quartz, opal, epidote and muscovite, by the removal of bases through the action of acid waters. Orthoclase is quarried at South Glastonbury and Middletown, Conn, ; Edgecomb and Brunswick, Me. ; Chester, Mass. ; Brandywine Summit, Pa. ; Tarrytown and Fort Ann, N. Y. Uses. — It is one of the constituents of porcelain and chinaware, chiefly to form the glaze, but partly mixed with the kaolin and quartz in the body of the ware. MICROCLINE. Composition.— KAlSijOj. General Description.— Like orthoclase, except that the macro axis is at 89° 30' to the vertical instead of 90°, and the basal cleavage often shows fine striations. In thin basal sections between crossed nicols it shows a peculiar interlaced structure due to two series of twin lamellae which cross nearly at right angles as in Fig. 587. „ „ Optically — . Axial plane nearly normal to the brachy pinacoid. SjgBJllt jj'j}^ Physical Characters. — Essentially as in orthoclase. Sp. gr. 2.54 to 2.57, and cleavage at 89° 30' instead of 90°. Before Blowpipe, Etc. — As for orthoclase. Remarks. — Includes varieties, Amazon stone, perthite, chesterlite, etc., formerly grouped under orthoclase. Often interlaminated wiih albite or orthoclase. Anorthoclase . A triclinic sodium-potassium feldspar found mainly in the lavas of Pantellaria. Color, lustre and hardness the same as for other feldspars. Cleavage close to 90°. Sp. gr., 2.59. Distinguished by its optical characters. ALBITE.— Soda Feldspar, Pericline. Composition. — NaAlSigOg. General Description. — Pure white,, granular, masses or in straight or curved laminae. Less frequently in white or colorless triclinic crystals, usually small. SILICA AND THE SILICATES. 355 Crystallization. — Triclinic. Angles a = 94° 3'; /9=ii6° 29'; 7- = 88° 9'. Axes ^ : 1^ :c = 0.633 : I : 0.558. Simple forms, Fig. 588, usually show both hemi prisms 7mLnd -Af, base c, brachy pinacoid d and other modifying planes. Angles mM= 120" 46'; C7H= 114° 4.1'] cM= 110° 50'; bm= 119" 34'. EiG. 588. Fig. 589. Fig. 590. Twinning by albite law (twinning plane b), Fig. 589, if repeated, results in striations on c, while by pericline law (twinning axis, the macro axis), Fig. 590, the striations are on b. Optically +, with weak refraction and double refraction. Thin sections with polarized light show parallel bands due to the twin lamellae, and characteristic extinction angles. Physical Characters. H., 6 to 6.5. Sp. gr., 2.62 to 2.65. Lustre, vitreous. Transparent to opaque. Streak, white. Tenacity, brittle. Color, pure white, colorless, or tinted blue, gray, red, green. Cleavage at angle of 86° 24'. Before Blowpipe, Etc. — Fuses in small pieces to a white enamel and colors the flame deep yellow. Insoluble in acids. Similar Species. — Differs from other feldspars in whiteness, granular, and lamellar structure and strong yellow flame. Remarks. — Frequently found in cavities and seams in granitic and schistose rocks, especially those high in silica, often enclosing the rarer minerals, tourmaline, beryl, chrysoberyl, topaz, etc. Is chief constituent of diorite. Not easily altered. OLIGOCLASE.— Soda Lime Feldspar. Composition. — ^(NaAlSisOs) + CaAlgSijOs. « = 2 to 6. General Description. — Cleavable masses, usually with fine striations on the basal cleavage surface. Color greenish-white, also in reddish or grayish masses, sometimes with fire- like reflec- tions (sunstone). Less frequently in triclinic crystals. 356 DESCRIPTIVE MINERALOGY. Physical Characters. H., 6 to 7. Sp. gr., 2.65 to 2.67. Lustre, vitreous or pearly. Transparent to opaque. Streak, white. Tenacity, brittle. Color, greenish, white, gray, reddish, yellowish. Cleavage, at angle of 86° 32'. Before Blowpipe, Etc. — Fuses rather easily to a clear or enamel-like glass. Insoluble in acids. Remarks. — Of igneous origin, occurring with orthoclase and albite in rocks of the granite type and in lavas, tr-achyte, serpentine, etc. It alters to epidote, natrolite, etc. Good crystals are found at Fine and McConib, St. Lawrence County, N. Y. LABRADORITE.— Lime Soda Feldspar. Composition. — NaAlSijOg + ;2(CaAl2Si308). « = i, 2, or 3. General Description. — Dark gray cleavable masses, which frequently show beautiful changing colors, blue, gold, red, etc. Less frequently in small triclinic crystals or colorless and glassy or granular to flint-like. Physical Characters. H., 5 to 6. Sp. gr., 2.7 to 2.72. Lustre, vitreous or pearly. Translucent to opaque. Streak, white. Tenacity, brittle. Color, dark gray, greenish, brown, colorless, white. Cleavage, at angle of 86° 4'. Before Blowpipe, Etc. — Fuses rather easily to colorless glass. Partially soluble in hydrochloric acid. Remarks. — Labradorite is of igneous origin, usually accompanied by pyroxene, amphibole, menaccanite or magnetite, forming the gabbros, dolerytes, and other basic rocks ; but is notably absent in localities containing orthoclase and quartz. It alters readily to zeolites, calcite, datolite, etc. Found abundantly in the Adirondacks, N. Y., in the Wichita Mountains, Ark., in Quebec and in Labrador. Uses. — It is polished for ornaments, table tops, inlaid work, etc. ANORTHITE.— Indianite, Lime Feldspar. Composition. — CaAl2Si20g. General Description. — White or red granular masses (indian- ite), small to rather large, glassy, colorless, white, or reddish- yellowish triclinic crystals and gray or pink cleavable masses. SILICA AND THE SILICATES. 357 Physical Characters. H., 6 to 6.5. Sp. gr., 2.74 to 2,76. Lustre, vitreous. Transparent to opaque. Streak, white. Tenacity, brittle. Color, white, colorless, gray, yellow, red. Cleavage, at 85° 50'. Before Blowpipe, Etc. — Fuses with difificulty to a colorless glass. In fine powder, is decomposed by hydrochloric acid, some- times with gelatinization. The solution will yield a copious white precipitate on addition of sulphuric acid. Remarks. — Frequently of volcanic origin, often enclosing grains of chrysolite. THE METASILICATES. The Metasilicates are derivatives of H2Si03, and are described in the following order : Leucite. Pyroxene Group. — Enstatite, Hypersthene, Pyroxene, Spodu- mine, Wollastonite, Pectolite, Rhodonite. Amphibole. Beryl. Cyanite. loLiTE is an intermediate species between metasilicates and orthosilicates. Many of the hydrous silicates are also derivatives of metasilicic acid. LEUCITE. Composition.— KAl(Si03)2. ^'^- S9i- General Description. — Gray, translucent to ^ white and opaque, disseminated grains and trap- fy^ ezohedral crystals in volcanic rock. / / ;> 1 Crystallization. — Isometric externally, but na r with polarized light, showing double refraction xk. ' at all temperatures below 500° C. Physical Characters. H., 5.5 to 6. Sp. gr., 2.45 to 2.50. Lustre, vitreous to greasy, Translucent to opaque. Streak, white. Tenacity, brittle. Color, white or gray, or with yellowish or red tint. Before Blowpipe, Etc. Infusible. With cobalt solution, be- comes blue. Soluble in hydrochloric acid, leaving a fine powder of silica. 358 DESCRIPTIVE MINERALOGY. Remarks. — A constituent of lavas, sometimes the chief constituent. By alteration, changes to kaolin, mica, nephelite, orthoclase, quartz, etc. It is not common in America, but is found in the Leucite Hills, Wyoming, and also in the northwestern part of the same State. Very common in the Vesuvian lavas. Uses. — Leucite rock has long been used for millstones. EN STATITE.— Bronzite. Composition. — (Mg.Fe) SiOj, General Description. — Brown to gray or green, lamellar or fibrous masses, with sometimes a peculiar metalloidal lustre (bronzite). Rarely in columnar orthorhombic crystals. Physical Characters. — Translucent to opaque. Lustre, pearly, silky or metal- loidal. Color, brown, green, gray, yellow. Streak, white. H., 5.5. Sp. gr., 3.1 to 3.3. Brittle. Before Blowpipe, Etc. — Fusible on the edges. Almost insoluble in acids. With cobalt solution is turned pink. Remarks. — It is rare in quartzose rocks, but occurs frequently in meteorites and with chrysolitic, basaltic and granular eruptive rocks. Occurs also associated with chondrodite, apatite, talc, etc. By alteration it forms terpentine, talc, and limonite. HYPERSTHENE. Composition. — (Mg.Fe)Si03, with more iron than enstatite. General Description. — Dark-green to black, foliated masses or rare orthorhom- bic crystals, which grade into enstatite. Frequently shows a peculiar iridescence, due to minute interspersed crystals. Physical Characters. — Translucent to opaque. Lustre, pearly or metalloidal. Color, dark-green to black. Streak, gray. H., 5 to 6. Sp. gr., 3.4 to 3.5. Brittle. Before Blowpipe, Etc. — Fuses on coal to a black, magnetic mass. Partially soluble in hydrochloric acid. Remarks.— Hypersthene is common in certain granular eruptive rocks, gabbros, norites, etc. In thin sections hypersthene is often strongly pleochroic while enstatite is only weakly so. Hypersthene often also includes tabular brown scales. Bastite. — An alteration product of enstatite near serpentine in composition. It is usually foliated and of a yellowish or greenish color and has a peculiar bronze-like lustre on the cleavage surface. H., 3.5-4. Sp. gr. , 2.5-2.7. PYROXENE.— Augite. Composition.— RSiOj. R = Ca, Mg, Mn, Fe, Al, chiefly. General Description. — Monoclinic crystals. Usually short and thick, with square or nearly square cross-section, or octagonal and with well-developed terminal planes. Granular, foliated and columnar masses and rarely fibrous. Color, white, various shades of green, rarely bright green, and black. Crystallization. — Monoclinic. /9 = 74° lo'. Axesi:^:^ = 1.092 : I .-0.589. SILICA AND THE SILICATES. 359 Common forms : unit prism m, the pinacoids a, b and c, the negative and, more rarely, the positive unit pyramids 'p and /, the Fig. 592. Fig. 593. Fig. 594. Fig. 595. V / '^ I / / \ m \ i a/ V Diopside, Pitcairn, N. Y. Fig. 596. Diopside. Fassaite. Rossie, N. Y. De Kalb, N. Y. Fig. S97- Fig. 598. / ^ N Leucaugite, Sing Sing, N.Y. Augite. Augite twin. negative and positive pyramids v and v = a: b:2c. Angles are m.m=2,y° 10'; // = 131° 31' ; // = 120° 49' z;^=95"48'; cp = 146° il'; ?/ = 137° 58'; cv = 1 30" 6' ; cv= 114° ^ig'. Contact twins, twinning plane a, Fig. 598, are common. Also twin lamellae parallel c, shown by striations on the vertical faces and by basal parting, Fig. 599. Optically +. Axial plane b. Strong double refraction. Varying axial angle. Usually not strongly pleochroic. Physical Characters. H., 5.6. Sp. gr., 3.2 to 3.6. Lustre, vitreous, dull or resinous. Opaque to transparent. Streak, white to greenish. Tenacity, brittle. Color, white, green, black, brown. Cleavage, prismatic (angle 87" 10'). Russell, N. Y. 36o DESCRIPTIVE MINERALOGY. Before Blowpipe, Etc. — Variable. Usually fuses easily to dark glass, sometimes to magnetic globule. Not generally solu- ble in acids. Varieties. Malacolite or Diopside. —C3Mg{S\0,\. Usually white or pale- green. Hedenbergite.—{Csi.'Fe){S\0^i. Grayish-green. Aicgite.—Ch\e?^y CaMg(Si03)2, but containing also Al and Fe. Dark-green to black, and many others which grade into each other imperceptibly. Diallage. — Thin foliated pyroxene, green or brown in color. Similar Species. — Differs from amphibole, as therein described. Remarks. — Next to the feldspars, pyroxene is the most common constituent of igneous rocks. It occurs also in crystalline limestones and dolomites, and usually of some light-green or white color (diopside). In serpentine it is apt to be lamellar diallage. In granite it is usually green, and in eruptive rocks is dark-green or black augite. It alters to chlorite, serpentine, amphibole, etc. ACMITE, iEgirite. Composition. — NaFe ( SiOj ) 2- General Description. — Occurs in long, prismatic crystals of dark green or dark brown color. In acmite these are acutely terminated and in aegirite, bluntly. Also found needle-like and fibrous. Optically — . Axial plane the plane of symmetry. Acute bisectrix nearly normal to the base. Strongly pleochroic. • Small extinction angle in sections parallel to the plane of symmetry. Physical Characters. — Translucent. Lustre, vitreous. Color, green to dark- brown, sometimes green on interior and brown on exterior of crystal. Streak, yellowish. H., 6-6.5. Sp.gr., 3.5. Before Blowpipe, Etc — Fuses easily to a black, slightly magnetic globule, and colors the flame yellow. Only slightly affected by acids. SPODUMENE. Composition. — LiAI(Si03)2, with some sodium replacing lithium. General Description.— White, greenish-white and rarely em- erald-green, monoclinic crystals, sometimes of Fig. 600. . A < • .-., ^„^ enormous size. Also m masses. Character- \ ized by breaking in broad, smooth plates, in . \ addition to regular prismatic cleavage. ] ] Crystallization. — Monoclinic. Axes a : 1) ""■■" :'<:=i.i24: I : 0.636 ; /3 = 69° 40'. Common /y forms : the pinacoids a and b, the unit prism, m, "/ unit pyramid /, the pyramid v = a:b: 2c and the clinodome ^ = 00 a : b: 2c. Angles : mm = SILICA AND THE SILICATES. 361 2,'j°; pp=ii6° 29'; w=9i° 26'; ^^=72" 36'. Optically +. Axial plane b. Physical Characters. H., 6.5 to 7. Sp. gr., 3.13 to 3.20. Lustre, vitreous. Transparent to opaque. Streak, white. Tenacity, brittle. Color, white, pale-green, emerald, green, pink, purple. Before Blowpipe, Etc. — Becomes opaque, intumesces, swells and fuses to a white or colorless glass, coloring the flame purple- red, especially With hydrochloric acid. Insoluble in acids. Similar Species. — Distinguished by its tendency to split into thin pearly plates and by the red flame. Remarks. — Occurs in granitic rocks with garnet, tourmaline and the granite min- erals, quartz, feldspars and micas. It alters readily to a mechanical mixture of albite and mica. Important localities are Stony Point, N. C. ; Chesterfield and Huntington, Mass. ; BranchviUe, Conn. ; Pennington County, S. D., etc. Uses. — The variety Hiddenite is used as a gem. JADEITE. Composition. — NaAl (SiOj)2. General Description. — Tough,' compact translucent material of dark to pale green color. Physical Characters. — Translucent. Lustre, vitreous to pearly. Color, shades of green to nearly white. Streak, white. Very tough. H., 6.5-7. Sp. gr., 3.33-3.35. Before Blowpipe, Etc. — Fuses easily to a transparent glass. Not attacked by acids. Uses. — Is used as an ornamental stone. Also in prehistoric implements and orna- ments. Remarks. — It is one of the minerals included in the term jade, and occurs in place in Burma and possibly in China. WOLLASTONITE. Composition. — CaSiOj. General Description. — Cleavable to fibrous white or gray masses. Also in monoclinic crystals, near pyroxene in angle. Sometimes compact. Usually intermixed with calcite. Crystallization. — Monoclinic. Axes a : b : ^ = I.OS3 : i : 0.967; /? = 84° 30'. ^'°- ^°'- Common forms : unit prism m, unit dome o, Common lorms : unit prism m, unit aome o, < ^ c j ^^. pinacoids a and c and prism ^^ = i : |- ^ : 00 ^. ■" ^'""'/{" ■ ( i """\ Angles are: ;«;« = 87° 18'; zz r- ^ - -^° f^' ■ -^ U -' ■■ ' ' - L-^ = 139° 57'. Optically — . Axial plane ^. Han-isville, N. Y. 362 DESCRIPTIVE MINERALOGY. Fig. 602. Physical Characters. H., 4.5 to 5. Sp. gr., 2.8 to 2.9. Lustre, vitreous to silky. Translucent. Streak, white. Tenacity, brittle. Color, white, gray, or light tints of yellow, red, brown. Cleavage. — and ?'-? at angle of 84° 30'. Before Blowpipe, Etc. — Fuses with difficulty, coloring the flame red. Soluble in hydrochloric acid, generally effervescing and always gelatinizing. Similar Species. — Differs from pectolite and natrolite in red flame, difficulty of fusion, and absence of water. Tremolite does not gelatinize. Remarks. — Occurs in granular limestone, granite, basalt,lava, etc., with pyroxene, calcite, garnet, etc. By the action of carbonated or sulphurated waters it changes to calcite or gypsum. PECTOLITE. Composition. — HNaCa2(Si03)3. General Description. — White or gray radi- ating needles and fibres of all lengths up to one yard. Also in tough compact masses and rarely in monoclinic crystals. Physical Characters. — Translucent to opaque. Lustre, vitreous or silky. Color, white or gray. Streak, white. H., 5. Sp. gr., 2.68 to 2.78. Brittle. Before Blowpipe, Etc. — Fuses easily to a white enamel. Yields water in closed tube. Gelatinizes with hydrochloric acid. Remarks. — Occurs with zeolites, prehnite, etc., in cavities and seams of igneous rocks. RHODONITE. Composition. — MnSiO,, with replacement by Fe, Zn or Ca. General Description. — Brownish red to bright red, fine grained or cleavable masses and disseminated grains, often exter- nally coated with a black oxide. Sometimes in triclinic crystals either tabular parallel to c or sometimes like the forms of pyroxene. Crystallization. — Fig. 603 shows three pinacoids a, b and c, the hemi unit prisms in and M, and two quarter pyramids v, and ,v oi d : b : 2c. The important angles are mM=%'j'' 32'; <:;«=iix° 15', cM = Franklin Furnace. 93 37 • Wiehawken, N. J. Fig. 306. SILICA AND THE SILICATES. 363 Physical Characters. H.,5.5 to 6.5. Sp. Gr., 3.410 3.68. Lustre, vitreous. Transparent to opaque. Streak, white. Tenacity, brittle. Color, brownish-red to flesh-red, bright- red, greenish, yellowish. Cleavage, prismatic, angle ^•]° 38' and basal. Before Blowpipe, Etc. — Blackens and fuses easily with slight intumescence. With fluxes reacts for manganese and zinc. In powder is partially dissolved by hydrochloric acid, leaving a white residue. If altered may effervesce slightly during solution. Similar Species. — Rhodochrosite is infusible, dissolves com- pletely with effervescence in warm acids. Red feldspars are less fusible, and do not give manganese reactions. Remarks. — Occurs with iron-ore, franklinite, tetrahedrite, etc., and is altered by light, air, and carbonated waters to the oxides and the carbonates. AMPHIBOLE.— Hornblende. Composition. — RSiOg, R generally stands for more than one of the elements, Ca, Mg, Fe, Al, Na and K. General Description. — Monoclinic crystals usually with acute rhombic section ; columnar, fibrous and granular masses, rarely lamellar, sometimes radiated. Colors white, shades of green, brown, and black. Fig. 606. Fig. 604. Fig. 605. Russell, N. Y. Crystallization. — Monoclinic. Axes a:b:c =0.5 S 1:1: 0.294; /3 = 73°S8'. Common forms : unit prism m, pinacoids b, c and sometimes a, unit clino dome d and unit pyramid/. Angles are : mm = 124° 11'; an= 104° 8'; dd = 148=28'; // = 148° 19'. Twinning as in pyroxene, p. 359. Optically -\-, axial plane b. Strong double refraction. Often strongly pleochroic. 364 DESCRIPTIVE MINERALOGY. Physical Characters, H., 5 to 6. Sp. gr., 2.9 to 3.4. Lustre, vitreous to silky. Transparent to opaque. Streak, white or greenish. Tenacity, brittle to tough. Color, white, gray, green, black, brown, yellow and red. Cleavage, prismatic, angle of 124° 11'. Before Blowpipe, Etc. — Varies. Usually fuses easily to a colored glass, which may be magnetic. Not affected by acids. Varieties': Tremolite. — CaMg3(Si03)4, white to gray in color. Actinolite. — Ca(Mg.Fe)3(Si03)4, bright green or grayish-green. Hornblende and Edenite. — Aluminous varieties, black or green in color, with lustre something like horn. All of these occur in crystals and columnar to fibrous. Nephrite or Jade is compact and extremely tough, microscopi- cally fibrous, may have composition of tremolite or actinolite. Asbestus is in fine, easily separable fibres, white, gray, or greenish. Similar Species. — Differs from tourmaline in cleavage, crystal line form and tendency to separate into fibres. The differences between it and pyroxene are : Amphibole, prism angle and cleavage 124°; tough, often fib- rous, rarely lamellar, often blade-like or pseudo-hexagonal crystals. Pyroxene, prism and cleavage angle 87° ; brittle, rarely fibrous, often lamellar crystals, square or octagonal. Remarks. — Occurs with' pyroxene, serpentine, talc, magnetite, quartz, the feld- spars, etc., and forms by alteration, epidote, serpentine, talc, chlorite, iron-ores, etc. Much of the material passing under the name of asbestus is fibrous serpentine. The best of the pure material is imported from Germany and Italy. Producing mines in the United States are located in California, Wyoming and Oregon. North Carolina, Georgia, Pennsylvania and other States have large deposits, but the quality and mode of occurrence do not allow it to be profitably mined at present. For most purposes the fibrous serpentine of Canada is superior to any American asbestus. Uses. — Asbestus is made into cloth and boards, which are in- combustible and are good non-conductors of heat. It is used for roofing, coverings for steam pipes, piston packing, theatre curtains, firemen's suits, fire-proof paints and cements, and for lining safes. It is made into yarns, ropes and paper for fire-proof purposes. Nephrite or jade has had many uses in prehistoric times and in historic times among semi-civilized or non-civilized nations. It is the toughest of all known stones and in the stone age was used SILICA AND THE SILICATES. 36s for weapons and tools. In China and India and in ancient Mexico it was carved into ornaments, symbols of authority, sacrificial ves- sels, etc. It has had a false value as a cure for kidney diseases, and both its names are derived from words meaning " kidneys." Glaucophane. A sodium amphibole NaAl(Si03)2.FeMgSi03 blue in color and occurring in indistinct prisms or in columnar and fibrous masses especially in metamor- phic schists. Crystals show distinctly different colors when viewed by transmitted light through different faces. Uralite. An amphibole pseudomorphic after pyroxene, having the crystal form of pyroxene and cleavage of amphibole. Crocidolite. A blue to green asbestos like amphibole. An altered South African form of the compact mineral which has a peculiar changeable lustre is often used as a cheap gem under the name of ' ' tiger' s eye. ' ' BERYL. — Emerald, Aquamarine. Composition. — Gl3Al2(Si03)|,. General Description. — Hexagonal prisms, from mere threads to several feet in length. Usually some shade of green. Some- times in columnar or granular masses. Harder than quartz. Fig. 610. Fig. 607. Fig. 608. Crystallization. — Hexagonal. Axis = 1 50° 4' ; c^ = 135° 4'. Optically — . Low refraction and very low double refraction (a =1.5659; )-= 1.5703 for yellow light). Physical Characters. H., 7.5 to 8. Sp. gr., 2.63 to 2.8. Lustre vitreous. Transparent to nearly opaque. Streak', white. Tenacity, brittle. Color, emerald to pale-green, blue, yellow, white, red, colorless. Cleavage, imperfect basal and prismatic. Before Blowpipe, Etc.— Fuses on thin edges, often becom- ing white and translucent. Slowly dissolved in salt of phosphorus to an opalescent bead. Insoluble in acids. 366 DESCRIPTIVE MINERALOGY. Varieties. Emerald. — Bright emerald green, from the presence of a little chromium. Aquamarine. — Sky-blue to greenish-blue. Goshenite. — Colorless. Similar Species. — Harder than apatite, quartz or tourmaline. Differs in terminal planes from quartz. Lacks distinct cleavage of topaz. Remarks.— Occurs in granite, mica-schist, clay-slate, etc., frequently penetrating the other minerals, showing that it was formed before them.. It is associated with quartz, micas, feldspars, garnet, corundum, zircon, etc. By alteration, it forms kao- linite, muscovite, etc. Beryls are especially abundant at Ackworth and Grafton, N. H. ; Royalston, Mass.; Paris and Stoneham, Me.; Alexander County, N. C. ; the Black Hills of South Dakota, and Litchfield, Conn. Those at Ackworth and Grafton are sometimes of immense size. One crystal, near the railroad station of Grafton Centre, measures 3 feet 4 inches by 4 feet 3 inches on horizontal section, and is exposed for over 5 feet. Good emeralds have been obtained in this country from Alexander County, S. C, and especially from Stony Point. Aquamarines and other gem speci- mens have been obtained at Paris and Stoneham, Me.; Mount Antero, Colo., and several places in North Carolina. Emeralds of finest quality are obtained near Muso, United States of Colombia, also from India, Brazil, Siberia and Australia. Uses. — Emerald and aquamarine are cut as gems. CYANITE.— Kyanite Fig. 609. Composition. — (A10)2Si03, probably a basic metasilicate. * General Description. — Found in long triclinic blade-like crystals, rarely with terminal planes. The color is a blue, deeper along the center of the blades, and at times passes into green or white. Physical Characters. H., 5 to 7. Sp. gr., 3.56 to 3.67. Lustre, vitreous. Translucent to transparent. Streak, white. Tenacity, brittle. Color, blue, white, gray, green to nearly black. Cleavage, parallel to the three pinacoids. Before Blowpipe, Etc. — Infusible, with cobalt solution be- comes blue. Insoluble in acids. Remarks.- — Occurs chiefly in gneiss and mica schist, and must have been formed below 1300°, as at this temperature it is changed into fibrolite. It is associated with pyrophyllite, andalusite, corundum, etc., and is found throughout the corundum regions of Massachusetts, Pennsylvania, North Carolina, and Georgia. , * Dana places cyanite with the orthosilicates for convenience. s if 1 ° i SILICA AND THE SILICATES. 367 lOHTE.— Dichroite, Cordierite. Composition.— Mg3(Al.Fe)j(SiOJ<{Si03)4. General Description. — Short, six- or twelve-sided orthorhombic prisms and massive, glassy, quartz-like material. . Usually blue in color. The color is often deep blue in one direction and gray or yellow in a direction at right angles with the first. Physical Characters. — Transparent or translucent. Lustre, vitreous. Color, light to smoky blue, gray, violet or yellow. Dichroic. Streak, white. H., 7 to 7.5. Sp. gr., 2.6 to 2.66. Brittle. Cleaves parallel to brachy pinacoid. Before Blowpipe, Etc. — Fuses with difficulty, becoming opaque. With cobalt solution becomes blue-gray. Partially soluble in acids. Remarks. — Occurs in gneiss and sometimes in granite, rarely in volcanic rocks, and is formed by contact with igneous matter. It is easily altered to a soft lamellar or fibrous material of green or yellow color, and is rarely found entirely unaltered. ORTHOSILICATES. The Orthosilicates are derivatives of H^SiO^, as Zircon, ZrSiO^ • Phenacite, GljSiO^. Isomorphic mixtures are well represented by Biotite, (H.K)2(Mg.Fe)Al2(SiOj3; acid salts by Prehnite, HjCaj- Al2(SiOj3, and basic salts by Sillimanite, Al(A10)Si04. Haiiynite is an example of a crystalline mixture of an orthosilicate and a sul- phate. As a rule, the orthosilicates are less stable than the meta- silicates. The orthosilicates described here are : Nephelite, Hauynite, Lazurite, Garnet, Chrysolite, Phenacite, Wernerite, Vesu- viANiTE, Zircon, Topaz, Andalusite, Sillimanite, Datolite, Epidote, Allanite, Prehnite. Biotite, Phlogopite and Muscovite, although derivatives of orthosilicic acid, are, according to the system of Dana, classified as hydrous silicates, while the probable orthosilicates, Chondro- dite and Staurolite are classed as subsilicates. NEPHELITE.— Elaeolite. Composition.— 7 NaAlSiOj + NaAl(Si03)2. With partial re- placement of Na by K or Ca. General Description. — Small, glassy, white or colorless grains or hexagonal prisms with nearly flat ends, in lavas and eruptive rocks, or translucent reddish-brown or greenish masses and coarse crystals, with peculiar greasy lustre. Physical Characters. H., 5.5 to 6. Sp. gr., 2.55 to 2.65. Lustre, vitreous or greasy. Transparent to opaque. Streak, white. Tenacity, brittle. Color, white, colorless, reddish, brownish, greenish or gray. Cleavage, prismatic and basal. 368 DESCRIPTIVE MINERALOGY. Before Blowpipe, Etc. — Fuses to a colorless glass. When heated with cobalt solution, becomes blue. Soluble in hydro- chloric acid, with residue of gelatinous silica. Varieties. — The usually massive varieties, with greasy lustre, are called elseolite. Remarks. — Nephelite occurs in eruptive rocks and lavas. Elsolite occurs in granular, crystalline rocks such as syenite. Nephelite alters easily and is the source of many of the zeolites. Austin, Texas ; Litchfield, Me., and the Ozark Mountains, Arkansas, are important localities of elseolite. Nephelite is abundant in the lavas of Vesuvius. CANCRINITE. Composition. — HgNa^Ca ( NajCOj )2 Alg ( SiO^) j. General Description. — A yellovif to white (rarely blue) massive mineral usually associated with elEeolite and blue sodalite. Rarely in hexagonal prisms. Optically — . Physical Characters. — Translucent to transparent. Lustre, vitreous. Color, yellow, pink, blue, green, gray and white. Streak, white. H., 5-6. Sp. gr., 2.4-2.5. Before Blowpipe, Etc — Fuses easily with bubbling to a white glass. Yields water in closed tube. Effervesces in HCI when warmed, and if previously ignited it yields a jelly on evaporation. Remarks. — Found at Litchfield and Gardiner, Me.; Miask, Urals; Brevik, Nor- way and other localities. SODALITE. Composition.— Na4(AlCl)Al2(SiOj3. General Description. — Bright blue to -gray masses and embedded grains. Con- centric nodules resembling chalcedony and rarely dodecahedral crystals sometimes of a pale pink color. Physical Characters. — Transparent to translucent. Lustre, vitreous to greasy. Color, blue, gray, nearly white, pale pink. Streak, colorless. H,, 5.5 to 6. Sp.gr., 2.14-2.30. Brittle. Cleavage, dodecahedral. Index of refraction, yellow light, 1.4827. Before Blowpipe, Etc. — Fuses to a colorless glass. In closed tube the blue varie- ties become white and opaque. Soluble in hydrochloric acid with gelatinization. Remarks. — Found at Litchfield, Me., various localities in Montana, Quebec, and Ontario ; also occurs in Vesuvius lavas, at Kaiserstuhl, Baden ; and Miask, Urals. HAUYNITE. Composition.— 2(Na2Ca)Al.^(Si04l2. (Naj.CajSO^ possibly, but very complex and with varying proportions of Na and Ca. General Description. — Glassy blue to green imbedded grains, or rounded iso- metric crystals in igneous rock. Physicial Characters. — Translucent. Lustre, vitreous or greasy. Color, blue, green, red, yellow. Streak, white. H. 5.5 to 6. Sp. gr., 2.4 to 2.5. Brittle. Before Blowpipe, Etc. — Fuses slowly to a white glass, which will blacken silver. Gelatines with hydrochloric acid. Noselite.—Uk& haiiynite but containing little or no lime. SILICA AND THE SILICATES. 369 LAPIS LAZULI or LAZURITE.— Native Ultramarine. Composition. — An orthosilicate of sodium and aluminium, with a sulphate and a polysulphide of sodium. General Description. — Deep-blue masses intimately mixed with other minerals. Rarely in isometric forms. Physical Characters. — Translucent. Lustre, vitreous. Color, deep-blue, violet and greenish-blue. Streak, white. H., 5 to 5.5. Sp. gr., 2.38 to 2.45. Brittle. Before Blowpipe, Etc. — Fuses easily to a white glass, with intumescence. In closed tube, glows with a green light and yields water. Soluble in hydrochloric acid with evolution of hydrogen sulphide and residue of gelatinous silica. Uses. — It is employed in inlaid worl<, and before the invention of artificial ultra- marine it was very valuable as a durable, deep blue, color for oil paintings. GARNET. R' Ca, Mg, Fe or Mn. Composition.— R"3R"'2(SiO,)3. R'" is Al, Fe"' or Cr, rarely Ti. General Description. — Imbedded isometric crystals, either complete or in druses and granular, lamellar and compact masses. Usually of some brown, red or black color, but occurring of all colors except blue, and harder than quartz. Also found in alluvial material as rounded grains. Fig. 611. Fig. 612. Fig. 613. Fig. 614. Fig. 615. Fort Wrangell, Alaska. 370 DESCRIPTIVE MINERALOGY. Crystallization. — Isometric. Usually a combination of the dodecahedron d and the tetragonal trisoctahedron, n = a:2a: 2a, Fig. 614, or these as simple forms, Figs. 61 1, 612, or more rarely with the hexoctahedron, s = a : ^a : ^a. Index of refraction for red light 1.7645 to 1.7716. Physical Characters. H., 6.5 to 7.5. Sp. gr.,* 3.15 to 4.38. Lustre, vitreous or resinous. Transparent to opaque. Streak, white. Tenacity, brittle to tough. Color, brown, black, violet, yellow, red, white, green. Cleavage, dodecahedral, imperfect. Before Blowpipe, Etc. — Fuses rather easily to light brown glass, except in case of infusible chromium and yttrium varieties. Insoluble before fusion, but after fusion will usually gelatinize with hydrochloric acid. Bead reactions vary with composition. Varieties. Grossularite.~C&!,K\2{S\0^y White, pale yellow, pale-green, brown-red rose-red. Pyrope. — Mg3Alj(Si04),, Deep-red to nearly black, often trans- parent. Almandite.—Y^^I^4^\0^i. Fine deep-red to black. Includes part of precious and of common garnet. Spessartite. — Mn3Al2(Si04).,. Brownish-red to purplish hyacinth red. Andradite. — Ca3Fe2(Si04)3. Yellow, green, red, brown, black. Includes many of the common garnets. Uvarovite. — Ca3Cr2(Si04)3. Emerald green, small crystals. Remarks. — Garnet is common in schists, gneiss, etc., and also occurs in granites, limestone, serpentine, and even in volcanic rocks. By oxidation of their ferrous iron and by the action of carbonated waters, garnets are altered, forming calcite, iron ores, soapstone, serpentine, gypsum, etc. The common garnet is a very common mineral in many localities throughout the United States. Precious garnets are found on the Navajo Reservation, New Mexico ; in Southern Colorado, Arizona, Utah, Elliot County, Ky, ; Amelia County, Va. ; Oxford County, Me. ; and in North Carolina, Georgia, Montana, Idaho and Alaska. In Lewis and Warren Counties, N. Y. ; Raburn County, Ga., and Burke County, N. C, garnets are so plentiful that they are mined for use as an abrasive. Uses. — Thousands of tons are used as an abrasive material in- termediate in hardness between quartz and corundum. A marble * Magnesium varieties lightest. SILICA AND THE SILICATES. 371 containing large pink garnets is quarried at Morelos, Mexico, as an ornamental stone. Transparent red garnets are sometimes highly valued as gems, and the green variety is also sometimes cut. CHRYSOLITE.— Olivine, Peridot. Composition. — ^^(Mg.Fe),Si04, General Description. — Transparent to translucent, yellowish- green granular masses, or disseminated glassy grains, or olive- green sand. When containing much iron, the color may be reddish-brown, or even, by alteration, opaque-brown or opaque- green. Rarely in orthorhombic crystals. Crystallization. — Orthorhombic. Axes d:~b -.c = 0.4657 : i : 0.5865. Fig. 616 shows the pinacoids a, b and c, the unit forms of pyramid, prism, macro and brachy dome m, p, and d, the macro prism I = d : 2b : ca c and macro pyramid q = d : 2b : c. Prominent angles are mm =■ 130° 3'; //= 139° 55'; co ^ 128° 27'; cd= 130° 27'. Fig. 617. Fig. 616. Optically -\-. Axial plane i:. Acute bisectrix normal to a. Strong refraction and double refraction (/J =1.678 and 2V = ?,7° 46', for yellow light). In thin rock sections, Fig. 617, the outline, the distinct cleavage cracks and the frequent partial alteration to serpentine assist in its recognition. Physical Characters, H., 6.5 to 7. Sp. gr., 3.27 to 3.57. Lustre, vitreous. Transparent to translucent. Streak, white or yellowish. Tenacity, brittle. Color, yellowish-green to brownish-red. Before Blowpipe, Etc. — Loses color, whitens, but is infusible unless proportion of iron is large, when it fuses to a magnetic glob- ule. Soluble in hydrochloric acid with gelatinization of silica. 372 DESCRIPTIVE MINERALOGY. Similar Species.— Differs by gelatinization from green granular pyroxene. Is harder than apatite and less fusible than tourmaline. Remarks.— Of igneous origin, occurring in basalts, traps and crystalline schists, associated with such minerals as pyroxene, enstatite, amphibole, labxadorite, T:hromite, etc. By alteration of its ferrous iron and by hydration forms limonite and serpentine, and the excess of magnesia usually forms magnesite. Further change may alter the serpentine to magnesite, leaving quartz or opal. Found at Thetford, Vt., Webster, N. C. Waterville, N. H., also in Virgmia, Pennsylvania, Nevir Mexico, Oregon, etc. Small gems are found in the garnet and sapphire regions of New Mexico, Arizona, Colorado, and Montana. Uses. — Transparent varieties are sometimes cut as gems. Hyalosiuerite — A highly ferruginous variety of chrysolite, containing sometimes as high as thirty per cent, of ferrous oxide. Fayalite. Has nearly all of the Mg replaced by Fe so that the composition is that of a simple iron orthosilicate. H., 6.5. Sp. gr., 4.32. Fuses to a magnetic globule. PHENACITE. Composition.— GljSiO^ (GIO 45.55, SiOj 54.45 per cent.). Generai. Description. — Colorless, transparent, rhombohedral crystals, usually small, frequently lens shaped. Sometimes yellowish and sometimes in prismatic forms. Harder than quartz. Fig. 618. Fig. 619. Mt. Amero, Col. Florissant, Col. Crystallization. — Hexagonal. Class of third order rhombohedron p, 47. Axis c = 0.661. Prominent angles x x ^ 104° 3'; r7-^ 116° 36'. Optically -)- . Physical Characters. — Transparent to nearly opaque. Lustre, vitreous. Color, colorless, yellow, brown. Streak, white. H., 7.5 to 8. Sp. gr. , 2.97 to 3. Brittle. Cleavagf, prismatic. Before Blowpipe, Etc. — Infusible and unaffected by acids. Made dull blue by cobalt solution. Remarks. — Occurs with amazon stone, beryl, quartz, topaz, emerald, etc. , and is sometimes used as an imitation gem. WERNERITE.— Scapolite. Composition. — A silicate of calcium, and aluminum, of variable composition and containing also soda and chlorine. General Description: — Coarse, thick, tetragonal crystals, usually quite large and dull and of some gray, green, or white SILICA AND THE SILICATES. 373 color. Cleavage surfaces have a characteristic fibrous appear- ance. Also in columnar and granular masses. Fig. 620. Fig. 621. Usual form. - Meionite of Vesuvius. Crystallization. — Tetragonal. Class of third order pyramid, p. 29. Axis c = 0.438. Usually prisms of first order m, and second order a, and unit pyramid/. Angle //= 136° 15'. Op- tically — , with weak refraction and double refraction. Physical Characters. H., S to 6. Sp. gr., 2.66 to 2.73. Lustre, vitreous to dull. Opaque to translucent. Streak, white. Tenacity, brittle. Color, gray, green, white, bluish, reddish. Cleavage., parallel to both prisms. Before Blowpipe, Etc. — Fuses with intumescence to a white glass containing bubbles. Imperfectly soluble in hydrochloric acid. Remarks. — Wemerite has been formed by heat at or near fusion. It is most abun- dant in granular limestone near contact with granite or similar rock. It occurs with pyroxene, apatite, garnet, zircon, biotite, etc., and is changed to pinite, mica, talc, etc., by atmospheric influence. Especially abundant at Bolton, Mass. Other localities common in New England, New York, New Jersey and elsewhere. VESUVIANITE.— Idocrase. Composition. — Cag[Al(OH, F)] Al2(SiOJ|. with replacement of Ca by Mn, and Al by Fe. General Description. — Brown or green, square and octagonal prisms and radiated columnar masses. Less frequently in pyramidal forms or granular or compact. Crystallization. — Tetragonal. Axis c = 0.537. Usually the unit prism m with base c and unit pyramid p. Prismatic faces often vertically striated. Angles // = 129° 21'; <:/ = 142" 46'. 374 DESCRIPTIVE MINERALOGY. Optically— (rarely + ) with rather strong refraction but weak double refraction (a = 1. 7226; j- = 1-7325 for yellow light). Fig. 622. Fig. 623. Fig. 624. I ^ Vifc^ Monzoni, Tyrol. Physical Characters. H., 6.5. Sp. gr., 3.35 to 3.45. Lustre, vitreous to resinous. Translucent to opaque. Streak, white. Tenacity, brittle. Color, brown or green, rarely yellow or bl-ue Dichroic. Cleavage, indistinct, prismatic and basal. Before Blowpipe, Etc. — Fuses easily with intumescence to a green or brown glass. At high heat yields water in the closed tube. Very slightly affected by hydrochloric acid, but after igni- tion is dissolved leaving a gelatinous residue. Similar Species. — The crystals and the columnar structure dis- tinguish it from epidote, tourmaline, or garnet. The colors are not often like those of pyroxene. Remarks. — Vesuvianite occurs most frequently in metamorphic rocks, granular limestone, serpentine, chlorite, gneiss, etc., with garnet, muscovite, calcite, etc. It alters to talc, serpentine and calcite. Found at Parsonsfield and RumforJ Falls, Me., Warren, N. H., Newton, N. J., Amity, N. Y. Also in California, Ontario and Quebec. MELILITE. Composition.— Ca,2Alj(Si04)2 with Na, Mg and Fe replacing Ca and Al. General Description. — Occurs in short prisms and in tabular orthorhombic crys- tals, especially in leucite and nephelite rocks and in melilite basalt. Physical Characters. — Transparent to opaque. Lustre, vitreous. Color, honey- yellow to brown, green and white. Brittle. H. 5. Sp. gr. , 2.9. Before Blowpipe, Etc. — Fuses quite easily to a yellowish or green glassy globule. Gelatinizes with hydrochloric acid. ZIRCON.— Hyacinth. Composition. — ZrSiO, (ZrO 67.2, SiOj 32.8 per cent). General Description. — Small, sharp cut, square prisms and pyramids with adamantine lustre and brown or grayish color. Sometimes in large crystals and in irregular lumps and grains. SILICA AND THE SILICATES. 375 Crystallization.— Tetragonal. Axis i = 0.640. Common forms: unit prism m, unit pyramid/), second order prism a, and pyra- mids u=a: a: y and x= a: ^a : 3c. Angles // = 123° 19' ; 2m=g6° 51'; mu= 159° 48'; «;r= 148° 7'. Optically + with strong refraction and double refraction (« = 1-9239 ; r = 1-9628 for yellow light). Fig. 625. Fig. 626. Fig. 627. Fig. 628. r4^ — „— ->-k- w ^-^ I m — „<■■ Physical Characters. H,, 7.5. Sp. gr., 4.68 to 4.70. Lustre, adamantine. ' Transparent to opaque. Streak, white. Tenacity, brittle. Color, brown, reddish, gray, colorless, green, yellow. Cleavages, imperfect, parallel to both pyramid and the prism. Before Blowpipe, Etc. — Infusible, losing color and sometimes becoming white. Insoluble in acids or in soda. Remarks. — Zircon is one of the first formed rock constituents, and is common as an enclosure in the others, especially the older eruptive rocks, granular limestone schists gneiss, syenite, granite, and iron-ore. It is also found in alluvial deposits. Zircons have been mined at Green River, Henderson county, N. C, where they are especially abundant. Specimen localities are common throughout the United States and Canada. Uses. — As a source of zirconium oxide used in one variety of incandescent light. Transparent, red and brown varieties are cut under the name of hyacinth. Colorless or smoke varieties are called jargon, and are comparatively worthless. TOPAZ. Composition.— Ali^SieQjsFio or Al(Al(O.F2))SiO^. General Description. — Hard, colorless or yellow transparent orthorhombic crystals with easy basal cleavage. Also massive in columnar aggregates, and as rolled fragments and crystals in allu- vial deposits. 376 DESCRIPTI VE MINER ALOG Y. Crystallization. — Orthorhombic. d:b:c= 0.529 : i : 0.477 Prisms often vertically striated. Crystals rarely doubly termi- nated. The predominating forms are the unit prism m, brachy Fig. 629. Fig. 630. Fig. 631. Omi, Japan. prism / = 2 a : b : CO c (with predominance of / the section is often nearly square) ; base c, unit pyramid/ and dome /= 00 & : b : 2 c. Prominent angles are : nun = 1 24° 17'; // = 86° 49'; // = 141 " ^f(top)= 92° 42'. Optically +. Axial plane b. Acute bisectrix normal to c. Refractive indices and axial angles vary considerably for different localities. Physical Characters. H., 8. Sp. gr., 3.4 to 3.65. Lustre, vitreous. Transparent to nearly opaque. Streak, white. Tenacity, brittle. Color, colorless, yellow, pale-blue, green, white, pink. . Cleavage, basal perfect. Before Blowpipe, Etc. — Infusible, but yellow varieties may become pink. With cobalt solution the powder becomes blue. Slowly dissolved in borax. If powdered and heated with previ- ously fused salt of phosphorus in open tube the glass will be etched. Insoluble in acids. Remarks. — Probably always formed under the influence of heat. Occurs with minerals of similar origin in granite and gneiss, or less frequently in cavities in vol- canic rock. Associates are the granite minerals and apatite, fluorite, cassiterite, beryl, zircon, etc. Fine crystals of Topaz are found at Deseret, Utah, at Crystal Park, Cheyenne, and Devil's Head Mountain, Colo., Nathrop, Cal., Stoneham, Me., and Bald Mountain, N. H. Gems are also obtained from Siberia, Brazil, Japan, Australia, Mexico and other countries. Uses. — Transparent varieties are cut as gems. SILICA AND THE SILICATES. 177 ANDALUSITE,— Chiastolite. Composition.— Al(A10)Si04, (Al^Oj 63.2, SiOj 36.8 per cent.) General Description. — Coarse, nearly square prisms of pearl gray or pale red color, or in very tough, columnar or granular masses. An impure soft variety (chiastolite) occurs in rounded prisms, any cross section of which shows a cross or checkered figure, due to the symmetrical deposition of the impurities, Figs. 633 and 320. Fig. 632. Fig. 633. Fig. 634. Chiastolite, Sterling, Mass. Crystallization. — Orthorhombic. Axes a:~b:c = 0.986 : i : 0.702. Usually either the unit prism in, and base c, or these with the unit brachy dome d. Angles are mm = 90° 48' ; dd= 109° 50'. Optically—. Axial plane the brachy pinacoid. Acute bisec- trix normal to c. Colored varieties strongly pleochroic. Physical Characters. H,, 7 to 7.5. Sp. gr., 3.16 to 3.20. Lustre, vitreous. Transparent to opaque. Streak, white. Tenacity, brittle to tough. Color, rose-red, flesh-red, violet, pale green, white, pearl-gray. Cleavage, prismatic, imperfect at angle of 90° 48'. Before Blowpipe, Etc. — Infusible. In powder becomes blue with cobalt solution. Insoluble in acids. Remarks. — It occurs in clay slates and in gneiss and schists with cyanite, fibro- lite quartz, etc. It alters rather readily to cyanite or kaolin. Found in many localities in the New England States, also in Pennsylvania and California. Foreign localities are numerous. Transparent crystals are found in Minas Geraes, Brazil. SILLIMANITE or FIBROLITE. Composition.— Al(AlO) SiO^. General Description, — Long, almost fibrous orthorhombic crystals, and fibrous or columnar masses of brown or gray color. Physical Characters. — Transparent to translucent. Lustre, vitreous. Color, brown, gray, greenish. Streak, white. H., to 7. Sp. gr., 3.23 to 3.24. Tough. Cleavage, parallel to brachy pinacoid. 378 DESCRIPTIVE MINERALOGY. Before Blowpipe, Etc.— Infusible, becomes dark blue with cobalt solution. In- soluble in acids. Remarks.— Chiefly found in mica schist, gneiss, etc. Sometimes with andalusite. Uses.— In the stone age it was used for tools, weapons, etc., being second only to jade in toughness. DATOLITE. Composition.— Ca(B.OH)SiOt. General Description. — Highly modified, glassy, monoclinic crystals. Usually colorless, but also white or greenish. Also in compact, dull, white or pink masses, resembling unglazed porcelain. Fig. 635. Fig. 636. Fig. 637. Bergen Hill, N. J. "-V^ Lake Superior. Crystallization. — Monoclinic. /? = 89° 51'. Axes a:l: c = 0.634 : I : 1.266. Prominent forms are the pinacoids a and c, the unit prism m, negative unit pyramid /, unit clinodome d, clino prism / = 2« : ^ : 00 c, and positive hemi pyramid r = a : b : '^c. Important angles are mm = 115° 13' ; //= 103" 31' ; pp = 120° 55'; ^^=76° 37'- Physical Characters. H., 5 to 5.5. Sp. gr., 2.9 to 3. Lustre, vitreous. Translucent to nearly opaque. Streak, white. Tenacity, brittle. Color, colorless, white, greenish. Before Blowpipe, Etc. — In forceps or on charcoal fuses easily to a colorless glass, and if mixed with a flux of acid potassium sulphate and calcium fluoride and a little water it will color flame green. In closed tube yields water at a high heat. Soluble in hydrochloric acid, with gelatinization. Similar Species. — Differs from the zeolites in crystalline form and flame. Remarks — It is a secondary mineral found in igneous rocks and sometimes in met- allic veins. Usually occurs with the zeolites, prehnite, calcite, etc. Found at Bergen Hill and Paterson, N. J. ; at Hartford, Tariffville and Roaring Brook, Conn. Also in New York, Michigan, Massachusetts, California, etc. SILICA AND THE SILICATES. 379 ZOISITE— Thulite. CoMrosiTiON.— Ca^ Alj (Al. OH) (SiOJj. General Description. — Gray or green and rose red (thulite) columnar and fibrous aggregates. More rarely, deeply striated orthorhombic prisms with indistinct ter- minations and perfect cleavage parallel the brachy pinacoid. Physical Characters. — Transparent to opaque. Lustre, vitreous to pearly. Color, white, gray, brown, green, pink and red. Streak, white. H., 6-6.5. Sp. gr., 3.25-3.35. Optically +. Before Blowpipe, Etc. — Swells up and fuses easily to a glassy mass which does not readily assume globular form. Not affected by HCl before ignition, but after igni- tion it is decomposed with formation of jelly. Remarks. — Found at Ducktown, Tenn., Chesterfield, Mass., Uniontown, Pa., and many other American and foreign localities. EPIDOTE. CoMPOSiTON. — Ca2Al2(A10H)(SiOj3 with some iron replacing aluminum. General Description. — Coarse or fine Fig. 638. granular masses of peculiar yellowish-green ^ ; ^ v color, sometimes fibrous. Also in mono- V--- j-^ .A clinic crystals and columnar groups, from \ 1° vA yellow-green to blackish-green in color. Crystallization. — Monoclinic. /9 = 64°37.' Axes a:b: c = 1.579: i: 1.804. Fortheforms: ;« = unit prism, a and c pina- coids, p unit pyramid and unit dome, the angles are mm = 70° 4'; ca=ii5°23'; co=ii6°i8'. Crystals extended in direction of ortho axis. Optically—. Axial plane the clino pinacoid. Acute bisectrix nearly vertical. Refraction and double refraction both strong. Pleochroism strong. Sometimes shows colored absorption fig- ure when held close to the eye. Physical Characters. H., 6 to 7. Sp. gr., 3.25 to 3.5. Lustre, vitreous. Transparent to opaque. Streak, white. Tenacity, brittle. Color, yellowish-green to nearly black and nearly white, also red and gray. Cleavage, basal, easy. Before Blowpipe, Etc. — Fuses easily with intumescence to a dark, usually slightly magnetic, globule. At high heat yields water. Slightly soluble in hydrochloric acid, but if previously ignited, it dissolves, leaving gelatinous silica. Remarks. — Formed chiefly by alteration of the feldspars, hornblende or biotite, etc. and is common in many crystalline rocks, often accompanying beds of iron in these rocks. It is not readily altered. Common throughout New England and many of the western States, 38o DESCRIPTIVE MINERALOGY. PlEDMONTiTE. — A. red manganiferous epidote. Crystals show different colors by transmitted light when viewed through different planes. FG.639. AXINITE. Composition. — An orthosilicate containing especially boron, aluminium, and calcium with some iron and man- ganese. General Description. — Occurs in acute-edged triclinic crystals, see Fig. 639, usually of clove brown, bluish or yellow color. Also occurs lamellar or massive of a bright glassy lustre. Physical Characters. — Translucent to transparent. Luster, highly vitreous. Color brown, bluish, yellow, gray and greenish. Streak, white. H., 6.5-7. Sp. gr., 3.27— 3.25. Optically — . Before Blowippe, Etc. — Fuses easily with bubbling to a dark greenish or black glassy globule. Reacts for boron. Gelatinizes with HCI after ignition. Remarks. — Fine crystals are obtained in Bourg d'Oisans, Dauphine ; and Mt. Skopi, Switzerland. ALLANITE. Composition. — -Analogous to epidote, but a silicate of the cerium and yttrium groups with lime and iron. General Description. — Pitch black or brownish embedded veins and masses and fiat tabular or prismatic monoclinic crystals. Physical Characters. — Opaque. Lustre, submetallic or pitch-like. Color, pitch black or brown. Streak, nearly white. H., 5.5 to 6. Sp. gr., 3.5 to 4.2. Brittle. Before Blowpipe, Etc. — Fuses very easily, becoming strongly magnetic, and at high temperature yielding water. Usually gelatinizes with hydrochloric acid, but after ignition is insoluble. PREHNITE. Composition. — H2Ca2Al2(SiOJ3. General Description. — A green to gray- ish-white vitreous mineral. Sheaf-like groups of tabular crystals, united by the basal planes. Sometimes barrel -shaped crystals and frequent- ly reniform or botryoidal crusts with crystal- line surface. Physical Characters. H., 6 to 6.5. Sp. gr. Lustre, vitreous. Streak, white. Color, light to dark green or grayish-white. Bourg d' Oisans. 2.8 to 2.95. Translucent. Tenacity, brittle. Cleavage, basal. Before Blowpipe, Etc. — Easily fusible to a whitish glass con- taining bubbles. In closed tube yields a little water. Soluble in hydrochloric acid, and after fusion is soluble with a gelatinous residue. SILICA AND THE SILICATES. 381 Similar Species. — Resembles calamine or green smithsonite somewhat, but is more easily fused, and does not gelatinize unless previously ignited. Remarks. — Occurs in granite gneiss, trap, syenite, etc., as a secondary mineral derived from their alteration, and associated with other secondary minerals as datolite or the zeolites. Bergen Hill and Paterson, N. J., have furnished a ievf gem stones. Other localities are Farmington, Conn., the Tamarack and Quincy copper mines, Mich., Perry, Me., and Westport, N. Y. Uses. — To a limited extent has been cut as a gem. BASIC OR SUBSILICATES. Made a division by Dana because their constitution is not defi- nitely settled, though probably each belongs to one of the preced- ing groups. Here are described Chondrodite, Tourmaline, and Stauro- LITE. CHONDRODITE. Composition.— HjMgjgSigOjjF,, or (Mg.re)i3(Mg.F)^(MgOH)2(Si04)8, with some iron replacing magnesium. General Description. — The chemical compound occurs as three crystallograph- ically distinct species, chondrodite, humite, clinohumite. Chondrodite proper consists of compact brown masses or disseminated grains and yellowish-brown to red, mono- clinic, pseudo orthorhombic, crystals of great complexity. Physical Characters. — Translucent. Lustre, vitreous. Color, brown, garnet- red, light to dark yellow. Streak, white. H., 6 to 6.5. Sp. gr., 3.1 to 3.2. Brittle. Before Blowpipe, Etc. — Infusible, sometimes blackens and then turns white. Fused with powdered salt of phosphorus glass will yield fluorine. Soluble in hydro- chloric acid with gelatinization. Remarks. — Chiefly found in crystalline limestone or with other magnesium minerals. Alters to serpentine. TOURMALINE.— Schorl. Composition.— Ri8B2(Si05),. R chiefly Al, K, Mn, Ca, Mg, Li. General Description. — Prismatic crystals, the cross sections of which frequently show very prominently a triangular prism. Color, usually some dark smoky or muddy tint of black, brown or blue, also bright green, red, and blue, or rarely colorless. Some- times the centre and outer shell are different colors, as red and green. Sometimes the color is different at two opposite ends. Occurs also columnar in bunches or radiating aggregates and in compact masses. 382 DESCRIPTIVE MINERALOGY. Fig. 641. Fig. 642. Fig. 643. Crystallization. — Hexagonal. Hemimorphic class, Axis c = 0.448. Prevailing forms : trigonal prism in, second order prism «, unit rhombohedron p, negative rhombohedron f = a : co a : a : 2c. Angles are: pp = 133° 8';#= 103° ; mp = iiy° 20'. Optically—. Strongly dichroic, absorption very marked for rays vibrating parallel to the vertical axis. Double refraction rather strong. Physical Characters. H., 7 to 7.5. Sp. gr,, 2.98 to 3.20. Lustre, vitreous or resinous. Transparent to opaque. Streak, white. Tenacity, brittle. Color, black, brown, green, blue, red, colorless. Cleavage, difficult, parallel to R and i-2. Before Blowpipe, Etc. — Usually fuses, sometimes very easily. With a paste of KHS04,CaF2 and water it yields a green flame. Insoluble in acids, but after strong ignition gelatinizes. Similar Species. — Differs from hornblende in hardness, crystal- line form and absence of prismatic cleavage. Differs from garnet or vesuvianite in form, difficult fusion, and green flame. Remarks. — Occurs in crystalline rocks : granite, gneiss, mica-schists, crystalline limestone, etc., with many associates. By alteration it forms cookeite, lepidolite, talc, and chlorite. Tourmalines of gem value have been obtained in some quantity from Paris, Auburn, and Hebron, Me., and from Riverside county, California. Uses. — Transparent, red, yellow, and green varieties are cut as gems. Thin plates are used to polarize light. STAUROLITE. Composition.— Fe(A10)4(A10H)(SiOj2, but varying. May con- tain Mg or Mn. General Description. — Dark brown to nearly black ortho- rhombic prisms often twinned, or in threes, crossing at 90° and 120°. Surfaces bright if unaltered. Very hard. SILICA AND THE SILICATES. 383 Crystallization. — Orthorhombic. Axes ^ :<5 : ^ =0.473: i: 0.683. Usual forms: unit prism m, unit dome o and pinacoids b and c. Frequently in twins crossed nearly at right angles, Fig. 645, or nearly at 60", Fig. 263. The important angles are: ot;« = 129° 20' Optically +. Axial plane the macro pinacoid. normal to c. CO = 124° 46'. Acute bisectrix, Fig. 644. Fig. 645. m Physical Characters. H., 7 to 7.5. Sp. gr., 3.65 to 3.75. Lustre, resinous or vitreous. Translucent to opaque. Streak, white. Tenacity, brittle. Color, dark brown, blackish-brown, gray when weathered. Cleavage, parallel to brachy pinacoid. Before Blowpipe, Etc. — Infusible, except when manganiferous. Partially soluble in sulphuric acid. Remarks. — Occurs chiefly in schistose roclc with andalusite, garnet, tourmaline, cyanite, etc., but is not found in schists rich in amphibole. Abundant at Claremont, Grantham, and Lisbon, N. H., at Windham, Me,, Chesterfield, Mass., Litchfield, Conn., and several other localities in New England. Also in New York, North Carolina, Georgia, and Pennsylvania. HYDROUS SILICATES. Compounds containing water of crystallization with certain closely related species in which the water plays the part of a base or is in doubt. The minerals described here are : Zeolite Division. — Apophyllite, Heulandite, Stilbite, Chab- AZITE, AnALCITE, NaTROLITE. Mica Division. — Muscovite, Biotite, Phlogopite, Lepidolite, Prochlorite. Serpentine and Talc Division. — Serpentine, Talc, Sepiolite. Kaolin Division. — Kaolinite, Pyrophyllite. 384 DESCRIPTIVE MINERALOGY. ZEOLITES. The zeolites are a group of silicates, all of which are of a sec- ondary origin and are usually found in the seams or cavities of basic igneous rocks, such as basalt or diabase, and less frequently in granite or gneiss. They are similar to the feldspars in constituents and combining ratios, and are chiefly formed from the feldspars and from nephe- lite, leucite, etc. Most of them fuse easily, with appearance of boiling, and all contain water of crystallization. The hardness varies from 3.5 to 5.5, and the specific gravity from 2.0 to 2.4. APOPHYLLITE. Composition. — Hi^KjCagfSiOj)^ + 9H2O, with replacement by fluorine. General Description. — Colorless and white or pink, square crystals. Sometimes flat, square plates or approximate cubes ; at other times pointed and square to nearly cylindrical in section. Notably pearly on base or may show in vertical direction a peculiar — fish eye — internal opalescence. Found occasionally in lamellar masses. Crystallization.— Tetragonal. Axis c= 1.252. Usually com- binations of unit pyramid /, base c, and second order prism a. Angle //= 104°; cp= 119° 28'. Prism faces vertically striated. Fig. 646. Fig. 647. Fig. 648. V '-■a Fig. 649. Physical Characters. H., 4.5 to 5. Sp. gr., 2.3 to 2.4. Lustre, vitreous or pearly. Transparent to nearly opaque. Streak, white. Tenacity, brittle. Color, colorless, white, pink or greenish. Cleavage, basal. SILICA AND THE SILICATES. 385 Before Blowpipe, Etc. — Exfoliates and fuses to a white enamel. In closed tube yields water. In hydrochloric acid forms flakes and lumps of jelly. Remarks. — Occurs in volcanic rocks and mineral veins with zeolites, datolite, pec- tolite, etc. It is a secondary mineral. HEULANDITE. Composition. — 'ii.^C&^.\{ SiOj)^ + 3H2O. General Description, — Monoclinic crystals, with very bright, pearly cleavage surfaces. The face parallel to cleavage is also bright pearly, and is less symmetrical than the corresponding face of stilbite. Physical Characters. — Transparent to translucent. Lustre, pearly and vitreous. Color, white, red, brown. H., 3.5-4. Sp. gr. , 2.18-2.22. Brittle. Cleaves parallel to pearly face. Before Blowpipe, Etc. — Exfoliates and fuses easily to white enamel. In closed tube yields water. Soluble in hydrochloric acid, with residue of fine powder. STILBITE.— Desmine. Composition. — H^ ( Na^. Ca ) Fig. 650. Al,(Si03), + 4H,0. General Description. — Tab- ular crystals, "of white, brown or red color, pearly in lustre on broad faces and frequently united by these faces in sheaf-like groups. Sometimes globular or radiated. Cape Blomidon, N. S. Crystals are orthorhombic in appearance, but really complex monoclinic twins. Physical Characters. H., 3.5 to 4. Sp. gr., 2.09 to 2.2. Lustre, vitreous or pearly. Translucent. Streak, white. Tenacity, brittle. Color, yellow, brown, white, red. Cleavage, parallel to pearly face. Before Blowpipe, Etc. — Swells and exfoliates in fan shapes, and fuses easily to a white, opaque glass. Yields water in closed tube. Soluble in hydrochloric acid, with a pulverulent residue. Remarks.— Occurs with other zeolites. CHABAZITE. Composition.— (Ca, Na,)Al2(Si03), + 6Hp. General Description. — Simple rhombohedral crystals, almost 386 DESCRIPTIVE MINERALOGY. cubic, also in modified forms and twins. Faces striated parallel to edges. Color, white, pale-red and yellow. Physical Characters. H., 4 to 5. Sp. gr., 2.08 to 2. 16. Lustre, vitreous. Translucent, transparent. Streak, white. ■ Tenacity, brittle. Color, white, red, yellow. Cleavage, parallel to the unit rhombohedron. Crystallization. — Hexagonal. Scalenohedral class, p. 39. Axis c = \ .086. Unit rhombohedron p and negative rhombo- hedra e ^= a : 00 a : a : y^c and f = a : Island of Cyclops. trisoctahedrons or modified cubes, rarely granular and compact with concentric structure. SILICA AND THE SILICATES. 3S7 Crystallization. — Isometric. The tetrahexahedron n= a : 2a : 2a is most frequent sometimes modified by the cube a or do- decahedron d, and in some crystals the cube predominates. Physical Characters.— H„ 5 to 5.5. Sp. gr., 2.2 to 2.29. Lustre, vitreous. Transparent to opaque. Streak, white. Tenacity, brittle. Color, white, colorless, greenish, red. Before Blowpipe, Etc. — Fuses easily and quietly to a clear, colorless glass. Yields water in closed tube. Gelatinizes with hydrochloric acid. Remarks. — A secondary mineral, usually with other zeolites. NATROLITE. Composition.— Na,Al(A10) (5103)3+ 2H,0. ^ig. 657. General Description. — Colorless to white, slender, nearly square prisms, with very flat pyramids. Usually in radiating and interlac- ing clusters and bunches. Also fibrous gran- ular and compact. Crystallization. — Orthorhombic. Axes d:b:c =0.979: 1:0.354. mm (angle of X o / Wood Cliff. N. J. prism) =91 14 . Physical Characters. H., 5 to 5.5. Sp. gr., 2.2 to 2.25. Lustre, vitreous. Transparent to opaque. Streak, white. Tenacity, brittle. Color, colorless, white, yellow, red. Cleavage, prismatic. Before Blowpipe, Etc. — Fuses very easily to a colorless glass. In closed tube, yields water. Soluble in hydrochloric acid, with gelatinization. Similar Species. — Differs from pectolite in square cross-sec- tion and fusion to a clear, colorless glass. Remarks, — Occurs with other zeolites and with prehnite, calcite and datolite. THOMSONITE. Composition.— (Ca.Na2) 2 Al4(Si04)4-|-5 H^O. General Description. — Usually either radiating fibres or slender prismatic crys- tals or else spherical with fibrous structure radiating from several centres and of differ- ent colors. More rarely distinct orthorhombic prisms. Physical Characters. — Translucent to transparent. Luster, vitreous to pearly. 388 DESCRIPTIVE MINERALOGY. Color white to colorless when pure, also greenish, reddish and yellow. Streak, white. Brittle. H., 5-55. Sp. gr., 2.3-2.4. Optically +. Before Blowpipe, Etc. —Yields water in closed tube. Fuses readily with bubbling to a white glassy globule. Gelatinizes with hydrochloric acid. THE MICA DIVISION. The micas and chlorites are characterized principally by the very easy perfect basal cleavage, the monoclinic crystals with prism angles of closely 1 20°, which usually appear either hexagonal or orthorhombic. Cleavages show the interference figure because the acute bisectrix is nearly normal to the base. In all the species a blow from a conical point upon a cleavage surface develops a so- called percussion figure, consisting of three cracks, one parallel to the plane of symmetry, the others at definite angles to this. The relative position of axial plane and principal line of the percussion figure and the axial angle give convenient distinctions. MUSCOVITE.— Potash Mica, White Mica, Isinglass. Composition. — H2(K.Na)Al3(SiOJ3, with some replacement by Mg or Fe. General Description. — Disseminated scales and crystals, which cleave with great ease into thin, elastic, transparent leaves. Also in masses of coarse or fine scales sometimes grouped in globular and plumose forms. Fig. 659. Usually gray in color. Fig. 658. Fig. 659. Crystallization. — Monoclinic. /?=89°54'. ?«;« (the prism angle) = 120° 12'. Crystals usually rhombic or hexagonal in section, with rough faces, and usually tapering. Cleavage is ap- proximately at right angles to the prism. Optically — . Axial plane normal to b and nearly normal to c , that is, normal to the principal line of the percussion figure. Axial angle variable . but large, iE 50" to 70°. Pleochroism feeble. Absorption in sections normal to cleavage very strong. SILICA AND THE SILICATES. 389 Physical Characters. H., 2 to 2.5. Sp. gr., 2.76 to 3. Lustre, vitreous, pearly on cleavage. Transparent in laminae. Streak, white. Tenacity, elastic. Color, gray, brown, green, yellow, violet, red, black. Cleavage, basal, eminent. Before Blowpipe, Etc. — Fuses only on thin edges to a yellow- ish glass. Insoluble in acids. Similar Species. — Differs from talc or gypsum in being elastic. Is usually lighter colored than biotite. Remarks. — Muscovite is of both igneous and secondary origin. It occurs with quartz and feldspars, in granite, gneiss and mica schist and related rocks and more or less disseminated in other rocks, and it also is found formed from cyanite, topaz, feld- spars, corundum, etc. The most productive mica mines of the United States are in Mitchell, Yancey, Jackson and Macon Counties, S. C, and Groton, N. H. Other large deposits exist at Grafton, N. H. ; Las Vegas and Cribbensville, N. M., and Deadvvood and the Black Hills, S. D., many of which are intermittently mined. Also in Nevada, California, Colorado and Pennsylvania in quantity and quality fit for use. Large quantities of mica are annually imported from India. Uses. — As transparent material in doors of furnaces, stoves, etc. As insulating material in electrical apparatus, especially on the armatures of dynamos. As coating for spangling wall papers and such fabrics as brocade. Damourite. — An altered hydrous potassium mica in small scales or fibrous. Folia less elastic and of silky luster. BIOTITE. — Black Mica, Magnesium Mica. Composition. — An orthosili- Fig. 660. cate approximating (H.K)2)(Mg.- Fe),Al,(SiO,)3. General Description. — Like muscovite,but usually dark green' to black in color. It cleaves • into thin, elastic leaves. ^^^^^ ^.^^^ Craftsbury, Vt. ] Optically— . Axial plane usu- ally parallel to b ; that is parallel to the principal line of the per- cussion figure. Axial angle usually small, 2E varying O to 12°, rarely 50°. Pleochroism strong. 390 DESCRIPTIVE MINERALOGY. Physical Characters. H., 2.5 to 3. Sp. gr., 2.7 to 3.1. Lustre, pearly, vitreous, submetallic. Transparent to opaque. Streak, white. Tenacity, tough and elastic. Color, commonly black to green. Cleavage, basal, eminent. Before Blowpipe, Etc. — Whitens and fuses on thin edges. Decomposed by boiling sulphuric acid, with separation of scales of silica. Remarks. — Occurrence and associates like muscovite, but is more common than muscovite in the eruptive rocks. It is found in most of the muscovite localities, and is a very common constituent of rocks and soils in the form of small scales. It alters more readily than muscovite to chlorite or to epidote, quartz and iron oxide. PHLOGOPITE.— Amber Mica. Composition— R3Mg3Al(SiOJ3, where R=H,K, Fic 661. MgF. General Description. — Large and small, brownish-red to nearly black crystals. Usually oblong, tapering, six-sided prisms. Thin plates often show a six-rayed star by transmitted light. Optically. — Axial plane parallel to b, that is parallel to the principal line of the percussion figure. Axial angle small, but varying in same specimen. Pleochroic in colored varieties. Pooe's Mills, n!y. Physical Characters. H., 2.5 to 3. Sp. gr., 2.78 to 2.85. Lustre, pearly or submetallic. Transparent to translucent. Streak, white. Tenacity, tough and elastic. Color, yellowish-brown, brownish-red, green, colorless. Cleavage, basal eminent. Before Blowpipe, Etc. — Whitens and fuses on thin edges. In closed tube yields water. Soluble in sulphuric acid with separa- tion of scales of silica. Remarks. — Phlogopite is usually found in crystalline limestones or in serpentine. It occurs in enormous crystals in Ontario and Quebec, and in various localities through New York and New Jersey. Uses, — It is largely used in electrical work. LEPIDOLITE.— Lithia Mica. Composition.— R3AI (3103)3. R = Li,K, NaF, etc. General Description. — Scaly, granular masses of pale-pink color and gray crys- tals, with easy mica cleavage into elastic plates. SILICA AND THE SILICATES. 391 Physical Characters. — Translucent. Lustre, pearly. Color, rose, violet, lilac, gray, white. Streak, white. H., 2.5 to 4. Sp. gr., 2.8 to 2.9. Sectile. Cleavage, basal. _ Before Blowpipe, Etc. —Fuses easily to white glass. Colors flame purple-red. Partially soluble in hydrochloric acid. CLINOCHLORE.— Ripidolite. Composition. — HgMgjAl^SigOja. Fig- 662. General Description. — Green, white and rose-red crystals with cleavage like mica, the cleavage plates however being only slightly elastic. Also masses made up of coarse or fine scales and earthy. Physical Characters. — Transparent to translucent. Lustre, vitreous to pearly. Color, green to red. Streak, light green. H., 2-2.5. Sp. gr., 2.65-2.75. Cleavage perfect, mica- ceous. Laminae flexible but not elastic. Optically usually -j-. Pleochroic. Axial angle 20° to 90°. Before Blowpipe, Etc. — When highly heated yields much water in closed tube Fuses only on the edges to a yellow enamel. Only slightly affected by HCl. Remarks. — Found at West Chester and Texas, Pa.; Brewsters, N. Y. , and many foreign localities. PROCHLORITE. Fig. 663. Composition. — H^„(Fe.Mg)23Alj^Sii30go. General Description. — Dark-green masses, com- posed of coarse to very fine scales. Also tabular and curiously twisted six-sided crystals, which easily cleave into thin plates which are not elastic. Also fre- quently distributed as a pigment in other minerals. Optically -\-. Axial angle small, 2E= 0° to 30°. Pleochroism distinct. Physical Characters. H., i to 2. Sp. gr., 2.78 to 2.96. Lustre, feebly pearly. Translucent to opaque. Streak, white or greeni.sh. Tenacity, flexible, non-elastic. Color, grass-green to blackish-green. Cleavage, basal. Feel, slightly soapy. Before Blowpipe, Etc. — Whitens and then fuses to a nearly black magnetic glass. In closed tube yields water. Soluble in sulphuric acid. Remarks. — Formed by decomposition of mica and aluminous varieties of amphi- bole, garnet, pyroxene, etc. , and occasionally found in crystalline schists and serpen- tines. 392 DESCRIPTIVE MINERALOGY. Delessite, a dark-green massive mineral of scaly or short fibrous appearance. H. , 2- 5- Sp- gr-> 2.9, which yields water in closed tube and is decomposed by HCl with separation of silica. Found in cavities of amygdaloidal eruptive rocks. SERPENTINE AND TALC DIVISION. SERPENTINE. Composition. — H^MgjSigOg, with replacement by Fe. General Description. — Fine granular masses or microscop- ically fibrous. Also foliated and coarse or fine fibrous. Color, green, yellow or black, and usually of several tints dotted, striped and clouded. Very feeble, somewhat greasy lustre and greasy feel. Crystals unknown. Physical Characters. H., 2.5 to 4., Sp. gr., 2.5 to 2.65. Lustre, greasy, waxy or silky. Translucent to opaque. Streak, white. Tenacity, brittle. Color, green to yellow, brown, red, black, variegated. Before Blowpipe, Etc. — Fuses on edges. In closed tube, yields water. In cobalt solution becomes pink. Soluble in hy- drochloric acid, with a residue. Remarks. — A secondary mineral formed from chrysolite, amphibole, pyroxene, enstatite, etc. It is associated with these and with magnetite, garnierite, chromite, dolomite, etc. Serpentine asbestus is not produced in the United States, but large amounts are annually imported from the Thetford and Coleraine mines of Quebec. Massive serpentine, or Verd Antique marble, is quarried at Milford, Conn. Uses. — It takes a fine polish, and is used for ornamental work, as table-tops, mantels, etc. The fibrous variety, chrysotile, is used as asbestus. TALC— Steatite, Soapstone. Composition. — HjM g3(Si Oj)^. General Description. — A soft, soapy material, occurring foli- ated, massive, and fibrous, with somewhat varying hardness. Usu- ally white, greenish or gray in color. Crystals almost un- known. Physical Characters. H., i. Sp. gr., 2.55 to 2.87. Lustre, pearly or wax-like. Translucent. Streak, white. Tenacity, sectile. Color, white, greenish, gray, brown, red. Cleavage, into non-elastic plates. Feel, greasy. SILICA AND THE SILICATES. 393 Before Blowpipe, Etc. — Splits and fuses on thin edges to white enamel. With cobalt solution, becomes pale pink. Insoluble in acid. Varieties. Foliated Talc. — H = i. White or green in color. Cleavable into non-elastic plates. Soapstone or Steatite. — Coarse or fine, gray to green, granular masses. H., 1.5 to 2.5. French Chalk. — Soft, compact masses, which will mark cloth. Agolite, — Fibrous masses of H. 3 to 4. Rensselaerite. — Wax-like masses. H., 3 to 4. Pseudomorphous after pyroxene. Similar Species. — Softer than micas or brucite or gypsum. Further differentiated by greater infusibility, greasy feel, and the flesh-color obtained with cobalt solution. Remarks. — Talc is an alteration product of pyroxene, amphibole, muscovite, ensta- tite, etc., and occurs with dolomite, serpentine, magnesite, tourmaline, etc. An im- mense deposit at Gouverneur, N. Y., is mined, and the total output is ground for use in paper-making, etc. Large soapstone quarries are worked at Francestown, N. H. Chester, Saxon's River, Cambridgeport and Perkinsville, Vt., Cooptown, Md., and Webster, N. C. Massachusetts, New Jersey, Pennsylvania, Virginia and Georgia are also producing States. Uses. — Soapstone is cut in slabs for hearths, linings of stoves, sinks and other articles of refractory nature. It is ground and moulded into gas-tips, and used as a preparation for blackboards and as a fine quality of tinted plastering. Agolite is used to mis? with wood pulp in paper manufacture. Talc is used in soap, as a dressing for fine skin and leather, as a lubricant and as pencils, tailors' chalk, etc. SEPIOLITE.— Meerschaum. Composition. — H4Mg2Si30,o. General Description.— Soft compact white, earthy to clay- like masses, of very light weight. Rarely fibrous. Physical Characters. H., 2 to 2.5. Sp. gr., i to 2. Lustre, dull. Opaque. Streak, white. Tenacity, brittle. Color, white, gray, rarely bluish-green. Feel, smooth. 394 DESCRIPTIVE MINERALOGY. Before Blowpipe, Etc. — Blackens, yields odor of burning and fuses on thin edges. In closed tube yields water. With cobalt solution becomes pink. In hydrochloric acid gelatinizes. Similar Species. — Resembles chalk, kaolinite, etc., but is characterized by lightness and gelatinization with acids. Remarks.— Possibly formed from Magnesite. The name " meerschaum " refers to the fact that it will float on water when dry. Most of the material used for pipes is obtained from Turkey. It occurs in large amount in Spain, and in smaller quantities in Greece, Morocco and Moravia. There are no productive American localities. Uses. — As material for costly tobacco pipes. In Spain it is a building stone. In Algeria it is used as a soap. KAOLINITE.— Kaolin, China Clay. Composition. H^AljSijOg, with more or less iron, silica, and organic matter. General Description. — Compact and clay-hke or loose and mealy masses of pure white, yellow, brown, red and blue color. Also in white, scale-like crystals, with the lustre of satin. Usually unctuous and plastic. Physical Characters. H., 2 to 2.5. Sp. gr., 2.6 to 2.63. Lustre, dull or pearly. Opaque or translucent. Streak, white or yellowish. Tenacity, brittle. Color, white, yellow, brown, red and blue. Before Blowpipe, Etc. — Infusible. Yields water in closed tube. With cobalt solution, becomes deep blue. Decomposed by sulphuric acid, but insoluble in nitric or hydrochloric acids. Similar Species. — It is not harsh like infusorial earth and is softer than bauxite. Remarks. — Kaolinite is formed by alteration of feldspars and other silicates. Carbonated waters remove the basic oxides and part of the silica. Its associates are feldspars, corundum, diaspore, topaz, etc. In the United States kaolinite is mined at Okahumka, Lake County, Florida, at Sylva, Dilsboro and Webster, N. C, and at sev- eral places in New Castle County, Del., and Chester and Delaware Counties, Pa. Kaolin of poorer quality is obtained in Ohio and New Jersey, and many other de- posits are known throughout the Atlantic States. Uses. — It is the chief constituent of porcelain, chinaware, orna- mental tiles, etc. SILICA AND THE SILICATES. 395 PYROPHYLLITE.— Pencil Stone. COMPOSITION.^HAl(Si03)2. General Description. — Radiated folite or fibres and compact masses of soapy feeling and soft and smooth like talc. Physical Characters. — Translucent to opaque. Lustre, pearly or dull. Color, white, greenish, brownish or yellow. Streak, white. H., I to 2. Sp. gr., 2.8 to 2.9. Flexible. Before Blowpipe, Etc. — Whitens and fuses on the edges, and often swells and spreads like a fan. In closed tube yields water. Partially soluble in sulphuric acid. Remarks, — Occurs in large beds and as gangue of cyanite. Uses. — Extensively manufactured into slate pencils. TITANO-SILICATES. TITANITE.— Sphene. Composition. — CaSiTiOg. General Description. — Brown, green or yellow, wedge-shaped or tabular monoclinic crystals, with adamantine or resinous lustre. Also compact, massive. Rarely lamellar. Crystallization. — Monoclinic. /3=6o° 17'. Fig. 664. Axes a:~b:c= 0.755 • i ■ 0.854. Crystals very varied. Most common forms : pinacoids c and a, unit prism m, negative unit pyramid p, domes jr = « : 00 b : y^ c and s = (x a : b : 2c, and the pyramid 1= a:~b : y^c. Angles are : ;;/;«= 113° Diana, N. Y. 31'; //= 136O11'; //= 133" 53'. Optically -)-. Axial plane the plane of symmetry. Very large dispersion producing peculiar interference figure with many lem- niscates and colored hyperbolse. Physical Characters. H., 5 to 5.5. Sp. gr,, 3.4 to 3.56. Lustre, adamantine or resinous. Transparent to opaque. Streak, white. Tenacity, brittle. Color, brown to black, yellow, green, rarely rose-red. Cleavage, prismatic easily, pyramidal less easily. Before Blowpipe, Etc. — Fuses, with intumescence, to a dark glass, sometimes becoming yellow before fusion. In salt of phos- phorus after reduction, the bead is violet. Partly soluble in hydrochloric acid, completely so in sulphuric acid. Remarks. — Occurs both as original and secondary mineral derived from alteration of menaccanite, brookite, etc. Its associates are pyroxene, amphibole, feldspars, zir- con, iron ores, apatite, etc. Good gem stones have been found at Brewsters, N. Y.; Bridgewater, Pa., and Magnet Cove, Ark. Uses. — As a gem. PART IV. DETERMINATIVE MINERALOGY. CHAPTER XXXVI. TABLES FOR RAPID DETERMINATION OF THE COMMON MINERALS. In the tables which follow, the minerals are divided first into minerals of metallic lustre and minerals of non-metallic lustre. The minerals of metallic lustre are divided into forty-eight groups by eight horizontal divisions based on color and hardness and six vertical divisions based on the effect of the blowpipe flame on charcoal. From the minerals of non-metallic lustre a division, A, of, min- erals possessing a taste, that is, soluble in water, is set aside. The non-metallic minerals without taste, as Division B and C, are then divided into forty-four groups, the action of hydrochloric acid given in each four horizontal divisions, and the action upon char- coal, in B, and in the platinum forceps, in C, giving the vertical divisions. The species in each group are printed in heavy type or ordinary type, according to their importance. The symbols, I., T., H., O., M., Tri. before each name designate the system of cr}.'stallization. The formula following is expected to suggest confirmatory blow- pipe tests and the lines of fine type to suggest distinctive tests or characters. H signifies hardness, G, specific gravity, S. Ph., salt of phosphorus. The page reference to the complete descrip- tion of the species is also given. For accurate results these precautions must be taken : I. All tests should be made upon homogeneous material, prefer- ably crystalline, as the tests may be unreliable if the material is impure, unless the effect of the impurity upon the test is known. 398 DETERMINATIVE MINERALOGY. 2. The classifying tests must be decided, and, if weak, should be attributed either to improper manipulation or to the presence of some accidental impurity. 3. The lustre must be observed on a fresh fracture. 4. The determination must be confirmed by reference to the description of the species, and, when possible, by comparison with known specimens. 5. When the test is very close to a line of division it is better to look for the mineral upon both sides of the line. If, as may happen, a specimen belongs to a rare species not in- cluded in the scheme, it will not yield tests corresponding to any species therein and more elaborate tables will be needed. TABLE I.— MINERALS OF METALf' The Mineral Hea^" Gives Gaelic Odor. a .a — 03 .SSc H. Arsenic, p. 255, As Brittle. Blue flame. H. Antimony, p. 258, Sb Thick fumes. Green flame. I, Tetrahedrite, p. 269, Cu.SbjS, See opposite. In closed tube. 0. Leucopyrite p. 202, FeaAs^ Black sublimate. 1. Gersdorffite, p. 224, NlAsS Yellowish-brown sublimate. I. Gobaltite, p. 220, CoAsS, unalt'd. I. Smaltite, p. 221, (Co,]sri)Asa Black sublimate. I. Chloanthite, p. 225, (M,Co)As5 Black sublimate. O. Arseuopyrite, p. 200, FeAsS Eed sublimate, then black. Gives White Coatins but no Garlic Odok. H. Molybdenite, p. 262, MoS^ Soapy feel. Streak greenish. 0. Stlbnlte, p. 258, Sb^S^ Easy fusion. Dark-gray color. Blue-green flame. M. Sylvanite, p. 288, CAu,Ag)Te2 Eesidue yellow. -. Calaverite, p. 289, AuTe^ Eesidue yellow (gold). H. Tellurium, p.337,Te. No residue, 1. Hesslte, p. 281, Ag,Te Eesidue white (silver). H. Antimony, p. 258, Sb Brittle. Thick fumes. I. Stannite, p. 235, (Ca,Sn,Fe)S Coat blue by cobalt solution. I. TetraUedrite, p. 269, Cu,sbjS, Black streak. Color dark gray. I. UUmannite, NiSbS In closed tube, a faint white sub- limate. Gives Yellow Coating V THE Assay on Continued » — . Lead, p. 242, Fb H. Tetradymite, p. 254, Bi2(Ti Bluish-green flame. O. Bismuthinite, p. 253, BijS; Needles or masses. G=6.jl U O, Jamesonite, p. 244, Pbaobg, Fibres or needles. G=5.5 to H. Blsmutb, p.252, Bi. Arboi* 0. Aikinite, p. 253, PbCuBiS; Embedded prisms or massiv{ 1. Galenite, p. 242, PbS Cubic cleavage. G=7.4 to 7.i 0. Bournonite, p. 243, CuPbSi , Simple and cog-wheel crystal , G=5.7 to 5.9. 1. Clausthalite, p. 244, PbSe Odor of horse-radish. Q u (0 0. Enarglte, p. 268, CuaAsS^ Columnar. 1. Tennantite, p. 269, CujAsaS, Granular. 0. Stibnite, p. 258, Sb^Sj Very easy fusion. O. Stephanite, p. 283, AgsSbS^ Black streak. Fuses leaving Ac M. Polybasite, p. 284, (Ag.CajoSbSe Black streak. Cu with S.Ph. H. Pyrargyrlte, p. 282, AgaSbS, Purplish-red streak. I. Galenite, p. 242, PbS Cubic cleavage. G=7.4 to 7.1 I. Tetrahedrite, p. 269, CusSbjS, Tetrahedral or fine-grained. I. Sphalerite, p. 22s, ZnS Pale-brown streak. :. Dranlnite, p. 260, u.Pb.TK Botryoidal, Green bead S.1 R.F. H. NiCCOllte, p. 224 NlAs Color, copper-red. Streak black. O. Erennerite, p. 289, (AgAujTos Color brasB-yellow. 0*0 u OSS! Not S'dby Knife. Lie OR SUBMETALLIC LUSTRE. :ecl on Charcoal : EAR tAST. Gives Magnetic Besidub but NO Coating OR Garlic Odor. Gives Non-Magnetic Metal but no Coating or Gaelic Odor. 0. Stromeyerite, p. 281, (Ag,Gu)j.S 1. Amalgam, p. 280, AgHg Whitens copper. Not Peeviously Included. e,S)3 — . Mercury, p. 276, Hg Fluid globules. Entirely volatil- ized. 6. es'nt. S. bS3 8. I. Platinum, p. 290, Pt(re) Grains and scales. G. 14 to 19. I. Iron, p. 196, Fe Grains and masses. G. 7.3 to 7.8. I. Silver, p. 279, Ag Malleable. Silver streak. G=10 to 11. I. Platinum, p. 290, Pt. Grains and scales. G=14 to 19 I. Linnalte, p. 219, (Co,Ni),S4 Octahedrons or massive. H. Iridosmine, p. 290, (Ir,Os) Flat grains. i. I. Argentite, p. 280, Ag^S Sectile. Residue of silver. M. Tenorlte, p. 271, CuO Minute scales or earthy masses. H. Grapliite,p.34i, c Soapy feel. Shining streak. 0. FyrolUBite, p. 2I6,Mn02 Radiating or compact. Black streak. 0. Chalcocite, p. 266, Cu,s Brittle. Eesidue of copper. I. Alabandlte, p. 214, MnS Cubic cleavage. Green streak. 0. Manganite, p. 216, MnO(OH) Prismatic. Dark-brown streak. 1, etc. Ph. in — . Turgite, p. 207, re^OsiOH)^ Red streak. Decrepitates. 0. Goethite, p.207,FeO(OH) Yellow streak. Crystalline. — . Llmonlte, FejO„Fej(OH), Yellowish-brown streak, p. 207. M. Wolframite, (Fe.Mn)WO. Fuses easily. G=7.2 to 7.5, p. 212. H. Hematite, p. 204, Fe^Os Bed streak. Brilliant lustre. H. Hmejlite,p.206,(Fe,Mg)OTiOs Red streak. Violet S.Ph. in E.F. 1. Magnetite, p. 202, FcjO. Black streak. Magnetic. I. Franklinlte, (PeMnZn),04 Brown streak. White coat, p. 203. I. Cbromlte, p. 211, FeCrjO. Brown streak. Green in S.Ph. I. Perovskite, p. 317, CaTiOj VioletbeadS.Ph. inB.F. 0. Columbite, p. 212, FeCCbOaJ^ Brilliant lustre. G=5.3 to 7.8 1. Uranlnite, p. 260, u.Pb, Th, etc. Botryoidal. Green S. Ph. ni B.F. — . Fsilomelane, p. 217, H^MnOs Botryoidal. Brownish-black streak T. Hausmannite, p. 215, MnjO^ Twin pyramids. Chestnut-brown streak. T. Braunite, MnjOa.MnSiOa Black streak. Gelatinizes, p. 215. T. RutUe,p.237,T10, Violet bead S.Ph. in R.F. 0. Brookite, p. 238, TiO, VioletbeadS.Ph. in E.F. I. Bornlte, p. 267, Cu^FeSj Red-bronze fracture. H. muerite, p. 223, NiS Brassy needles or hair. I. Pentlandite,p. 224, (Fe,Ni)S Light brass-yellow. T. ehalcopyrlte, p. 267, CuFeS, Deep brass-yellow. H. Pyrrhotlte, p. 197, FenSn+i Bronze-yellow. Magnetic. I. Gold, p. 287, (Au,Ag) Golden streak. Malleable. I. Copper, p. 265 Cu Copper streak. Malleable. I. Cuprite, p. 270, CujO Brownish-red streak. Brittle. I. Pyrlte, p. 197, FeS^ 0. MarcaBlte, p. 199, FeS, TABLE II.— MINERALS OF A. Minerals with Decided Ta; Name. Taste. In the Forceps 0. F. THE Flame is COLOKED. Thj 1 TW. Sasaolite, p. 331, h,B03 M. Mirabillte, p. 296, NajSO.+lOHjO 0. Mascagnite, p. 297, (NHjjjSO. 0. Epsomlte.p. 318, MgSO^+VHjO H. Aphthltalfte, p. 291, (K.Naj^SO^ M. Borax, p. 332, Na^BjC+lOHjO M. Trona, p. 296, NajC03.NaHC03+2H20 1. Arsenolite, p. 257, ASjO, M. Alunogen, p. 327, AUCSO^jj+lSH^O M. Melanterite, p. 209, FeSO^VHjO 0. Goalarite, p. 229, ZnS04+7HaO 1. Kallnlte, p. 292, ka1(§0.,),+12H,o Tri. Chalcanthite, p. 272, CuSO^+SHjO M. Copiapite, p. 208, FeaFe(OH)3(S04)5l8HjO H. Soaa Nitre, p. 296, NaNOa I. Sal Ammouiae, p. 297, NH.Cl 0. Nitre, p. 292, KNOj 1. Sylvite, p. 290, KCl 0. Thenardite, p. 295, Na.SOi 1. Halite, p. 294, NaCl M. Glaubeiate, p. 295, Na^SO^CaSO^ M. Kainite, p. 292, MgSO«KCH-3H30 Acid, slightly saline. Bitter, cooling. Bitter, pungent. Bitter and salt. Bitter and salt. Alkaline, sweetish. Alkaline. Astringent, sweetish. Astringent. Astringent, sweetish. Astringent, nauseous. Astringent. Astringent, nauseous. Astringent, nauseous. Saline, cooling. Saline. Saline, cooling. Saline. Saline. SaUne. Saline. Saline. Yellowish green. Yellow. Violet. Yellow. Yellow. Violet. Emerald green. Yellow. Violet. Violet. Yellow. Yellow. Yellow. Violet. W M W M Be W Be W B. The Mineral is without Taste, but strongly hei I' 01 u > n CO Aksenical Odor. White Coating but no Arsenical Odor. Yellow Coa i — . Hydrozincite, p. 230, Zn3C03(0H)i H. 2 to 2.5. Chalky or pearly. T. Phosgenite, p. 248, (PbCl)2C03 Yellow coat with Bi flux. I. Sphalerite, p. 228, ZnS Evolution HaS. Brown to black color. H. smlthsonite, p. 230, ZnCOa H. 5. Vitreous, botryoidal, drusy. 0. Cerussite, i Greenish yello — . Bismutite, p Chocolate and i 1 2s>. 0. Calamine, n. 231, (ZnOH)3Si03 Water in closed tube. H. Willemite, p. 231, ZnjSiOi Anhydrous. 1 1 n .a u u a > X Is Dissolved with Formation of Jelly. M. Pectolite, p.362, HNa2Ca(Si03)3 Radiating splintery fibers, 0. Thomsonite, (NasCa)Ali,8iaO, P. 387. +|HsO M. WoUastonite, p. 361, Caslo^ T. ApophyUlte, n. 384, = n , H„K',6a,(S10a).,9H,0 Swells colors flame violet. H. Chatazite, p. 385, (Ca,Na^Al,{SiOa).+6HjO Intumesoes. Nearly cubic. 1. HaOynite, p. 368, 3(NasCa)Al,S04(S104)j Bounded grains. Sulphur react. I. Lazurite, p. 369, Na4(NaS3Al)Al2(SiO.)3 Intumesces. Deep blue color. M. DatoUte, p. 378, Ca(BOH)SiO« Intumesces. Green flame. I. Analclte, NaAl(S10a)a.HaO Quiet fusion, yellow flame. P. 336. 0. NatroUte, NaaAl.Si30,„-|-2HaO Quiet fusion. Slender prisms. P. 387. H. NepbeUte, NasAlaSi.Oai Strong yellow flame. Glassy or with greasy luster. P. 367. T. Melinite, Si,Al,Fe,Mg,Na, Ca Fuses with intumescence to grf or yellow glass. P. 374. JZ ■!-> i « OQ c (D •o 1 % c 1 It |8 Is It o o BO M. CryoUte, p. 323, AlNa^Fe Yellow flame. H=2.5. T. Wemerlte, Ca,Na,Al,SiOs Yellow flame. H=5to6. P. 372. I. Pluorite, p. 304, CaFj Eed flame. Cubic, fluorescent. M. Gypsum, p. 306, CaS04+2HsO Pale red flame. Water test. H=2. 0. Anhydrite, p. 300, CaSOi Pale red flame. H=3. 1. Boracite, p. 334, Mg,ajB„03„ Green flame. Pink by Co solution. M.StUbite,H4K,Al3CSiO,;a+4HjO Sheaf-like. Swells with heat. P. 385. M. Heulandite, p. 386, H» •c ea V Z IH V s a Tri. Albite, p. 355, NaAlSijO, Yellow flame. H=6. Tri. Ollgoclaae, p. 365, n(NaAlSi,Os.{CaAljSl,0,) Yellow flame. H=6. M. Petalite, p. 352, AlLi(Sia05)j Bed flame. Phosphorescent. G=2.4 + 0. Celestite, p. 300, SrSO^ Eed flame. G=3.9-|- M. Lepidollte, p. 390, BaAlCSiO,), Bed flame. Micaceous. 0. Barlte, p. 298, BaSO^ Green flame. G=4.3. 0. Zoisite, Cas(A10H)Ala(SI04)3 Columnar. No flame. P. 379. H. Tourmaline, EiaBjCSiOsji P. 381. M. Pyroxene, p. 368, BSlOa M. AmpMboIe, p. 3&, ESiO H. Beryl, p. 364,%eaAla(Si03). Tri. Albite, p. 355, NaAlSiaOa Yellow flame. H— 6. Tri, OUsOClase, p. 366, »(NaAl§iaOa)CaAIaSiaOa YeUow flame. H=6. M. Spodumene, LiAUSiOaJa Bed flame. Sphts in thin plates. P. 360. M. Pyroxene (Dlopsldelj p. 358, M. Ampblbole, p. 363 (TremoUte)' CaMgaSl^Oxi, M. Jadelte, p. 361, NaAlSiaOo Yellow flame. Compact. M. Glaucophane, p. 365, NaAf(Si03)a(Fe,Mg)Si03 Yellow flame. Massive. T. Vesuvianite, p. 373, CaaCAlOHFJAlaCSlO Brown to bright green crystals i columns. M. Titanite, p. 395, CaSiTlO. Wedge-shaped crystals. Boi with Sn and HCI violet. M. Epidote, CaaAla(A10H)(SiO Yellow green grains, fibers a crystals. P. 379. I. Garnet, p. 369, Spessarlite, MnaAla(SiO and Pyrope, MgaAUCSiOOa M. Pyroxene, (Ca,Mg,Fe)S10a Cleavage and prism angle 87°. P. 358? M. Amphibole, p. 363, Aotinoh Ca{Mg,Fei3(SI0 Cleavage and prism angle 126°. Tri. Axinite, HaE4(B0jAla(Si0 P. 380. Clove-brown, acute edged crystal lOUT METALLIC LUSTRE. :lo, a Fragment is Heated in tine Forceps at Tip of Blue Flame. Fdses with Difficulty. Infusiblh but in Powder Made Deep Blue by Cobalt Solution. Infusible, not Included Peevioublt. M. Barytocalclte, p. 300, (Ba,Ca)C03 Colors- flame yellowish green. 0. Strostlanlte, p. 302, SrCO, Colors flame crimson. H. Magneslte, p. 319, MgCO, White chalk-like masses. H. Rhodocbrosite, p. 218, MnCO, Pink to red. Flame is colored red by : H. Calcite,p.3ll,CaCOs G. 2.71. Ehombohedral cleavage. 0. Aragonite, p. 310, CaCOa G=2.95. H. Dolomite, p. 314, (CaMg)C03 Slow effervescence 01 lumps. 1 M. WoUastonite, p. 361, CaSiO, Yellow-red flame. H 4.5 to 5. Tri. Anorthite, p. 356, CaAlsSUOs Yellow-red flame. H 6 to 6.5. -. SepioUte, p. 893, H.MgaSlaO,. Compact, earthy. Pink with cobalt solution. 0. Calamine, p. 2si, (ZnOH)jS103 White coat with soda. Water m closed tube. H. WUlemite, p. 231, Zn^SiO. White coat with soda. T. Thorite, p. 240, ThSiO^ H— 5. Orange to brown. H. Dioptase, p. 275, HjCuSiOi H=5. Emerald green. 0. Chrysolite, p. 371, (Mg.Fej^SiO^ H=7. Olive to gray-green. M. Chondrodite, HjMgiBSisOa^E^ H=8.6. Brown to yellow. V. 381, < 3. H. Apattte, p. 308, Ca,(F,Cl)(P04), Bed flame, green with H2SO4 T. ScheeUte, p. 316, CaWO. In Ph. S. with E. F. bead blue when cold. M. Colemanite, CajBeOn+SHjO Exfoliates. Flame green. P. 338. M. Herderite. Ca[BerOH,F)]P04 Crystals white to yellow. — . Serpentine, p. 8M, H^MgjSijOs H=4. Yields water. J justre greasy, 0. lolite, H2(Mg,Fei4AlBSi,„03, H=7 to 7.5. Blue vitreous. P. 367. M. Aluminlte, p. 327, AISSO11.9H3O H-lto2. White chalky masses. -. Bauxite, p. 326, ai,0(OH). Oolitic or like clay. 0. Wavellite, p. 329. Al,{OH2.(P004+9H30 Spheres and hemispheres of radiat- ing crystals. -. Turquols, Al3(0H),PO..H3O Sky blue to green with lustre of wax. P. 328. 1. Leucite, p. 357, KAl(Si03), Tetrag. trisoctahedrons. White or gray in color. M. Monazite, p. 240, (Ce,La.Di)(PO*) Resinous brown crystals or yellow grains. H. Brucite,p.818,MgCOH), Foliated or fibrous. Pink with Co solution. — . Wad, p. 217, Mn oxides. Dull earthy brown to black. -. Gamierite, p. 226, H3(Ni,Mg)SiO.+H,0 Deep green to pale green. Soft and friable. — . Obrysocolla,CuSi03+2H30 Green to sky-blue with waxy lustre. P. 274. 1 ■d i 6, 0. Talc, p. 392, H,Mg3(Si03)4 H=l. Soapy. Pink with Co solution. -. PyrophylUte, p. 895, HAlCSiOa)^ H=l to 2. Soapy. Blue by Co solu- tion. M.FTOClllOrite,p.391, Ha(Mg,Fe)aAl3Si30i„ H— 1 to 2. Dark green micaceous. After flision is magnetic. M. ainochlore, H,Mg.Al3Si30i, H=-2 to 2.6. Dark green, flexible, foliated. P. 391. M. Muscovite, H,(K,Na)Al3(Si04)3 H=2.5. Light colored mica. P. 388. M. PMogoplte, K.Mg,Al(SiO 4)3 H=2.5. Iflca in limestones. P. 890. M. BiOtlte J». 389, (KH)3(Mg,Fe),AU(SiO.)3 H=2.5.. Dark mica in granites. 0. Enstatite, p. 368, (Mg.FejSiOj H— 5.5. Foliated. Pearly lustre. M. Orthoclase, p. 362, KAISlaO, H— 6. Rectangular cleavage. Tri. Mlcrocline, p. 854, KAISIjOb H=6. Striations frequent. H. Tourmaline, RisBjCSiO")! _ H=7 to 7.5. Hemimorphic. P. 381. H. Beryl,p.364,Be3Alj(S103)o H— 7.5 to 8. Prismatic. M. Kaolinite, p. 394 H^Al^SijO, H— 2 to 2.5. Soapy feel. M. GibbBlte, p. 326, AlCOH), H— 2.5 to 3.5. Clay odor. H. Alunite, K(A103)(S04)j+3HjO H— 3.5 to 4. Small white cuboids. P. 328. M. Lazullte, p.329,EAl,(0H)3(P04)j H=5 to 6. Acute blue pyramids. Tri. Cyanite, p.366, (A10),Si03 H— 5. Blue bladed crystals, 0. Sillimanite, p. 377, Al(A10)Si04 H=6 to 7. Gray to brown crystals and fibers. 0, Diaspore, p. 326, AIO(OH) H=6.5. Pearly, pink to brown. 0. AndalUBite, p. 377, Al(A10)SiO. H— 7 to 7. 6. Squ are prisms. H. Phenacite, p. 372, BejSiOj H— 7.5 to 8. Resembles quartz. 1. Spinel, p. 319, MgAljOi H— 8. Octahedrons. 0. Topaz, p. 875, Al(Al(0F,)Si04 H— 8. Prisms with basal cleavage. 0. CliryBOljeryl, p. 830, BeAljOi H'-8.5. Tabular, yellow or green. H. Corundum, p. 824, AUp, H— 8-9 G— 4. Adamantine. T. Octahedrite, p. 238, riOa Brown or blue pyramids. Adaman- tine. T. RutUe,P.287,Ti03 Eed to black. Adamantine pris- matic, often needles. G=^2, T. Cassiterlte, p. 235, SnO, Brownish-black. Adamantine, pyra- midal and prismatic. G=6.8 to 7.1. H. Quartz, p. 346, SiOj H=7. G— 2.65. Very varied. H. Trldymite, p. 850, SiO, Minute tabular crystals. — . Opal, p. 350, SiO.nHjO H— 5.5 to 6.5. G— 2.1 to 2.2. Frac- ture conchoidal. T. Zircon, p. 874, ZrSlOi H=7.5. Pyramid and prism. 0. StauroUte, p. 382, FecW'CAlOHXSiO.) H=-7.6. Prisms. Usually twinned. H. Tourmaline, E,sB,(SiO.)4 H— 7.5. Hemimorphic. P. 881. 1. Garnet, p. 869, Uvarovite, CajCrjCSiO.), H— 7.5. Emerald green crystals. I. Diamond, p. 3«, C H=10. Adamantine. G=8.51. TABLE OF ATOMIC WEIGHTS. ACCORDING TO CLARKE (H=i). Element. Symbol. At. Wt. Aluminum Al 26.91 Antimony Sb 1 19. 52 Argon A ? Arsenic As 74-44 Barium Ba 136.39 Bismuth Bi 206.54 Boron B 10.86 Bromine Br 79-34 Cadmium Cd III. 10 Calcium Ca 39- 7^ Carbon C 11.91 Cerium Ce 138.30 Cesium Cs 131 89 Chlorine CI 35.18 Chromium Ch S'-74 Cobalt Co 58-55 Columbium Cb 93-02 Copper Cu 63.12 Erbium Er 165.06 Fluorine F 18.91 Gadolinium Gd 155-57 Gallium Ga 69. 38 Germanium Ge 71-93 Glucinum Gl 1 Berylium Be J Gold Au 195-74 Helium He ? Hydrogen H i.oo Indium In 1 1 2. 99 Iodine 1 125.89 Iridium Ir 191.66 Iron Fe SS-6o Lanthanum La '37-59 Lead Pb 205.36 Lithium Li 6.97 Magnesium Mg 24.10 Manganese Mn 54-57 Zirconium Zr... Element. Symbol. At. Wt. 9.01 Mercury Hg 198-49 Molybdenum Mo 95-26 Neodymium Nd 139-70 Nickel Ni 58.24 Nitrogen, N 13-93 Osmium O^ 189.55 Oxygen O 15.88 Palladium Pd 105.56 Phosphorus P 30-79 Platinum Pt 193-41 Potassium K 38-82 Praseodymium Pr 142. 50 Rhodium Rh 102.23 Rubidium Rb 84.78 Ruthenium Ru 100.91 Samarium Sm '49- 13 Scandium Sc 43-7^ Selenium Se 78-42 Silicon Si 28.18 Silver Ag 107. 1 1 Sodium Na 22.88 Strontium Sr 86.95 Sulphur S 31.83 Tantalium Ta 1^1-45 Tellurium Te 126.52 Terbium Tb 158.80 Thallium Tl 202.61 Thorium Th 230.87 Thulium Tu 169.40 Tin Sn 118.15 Titanium Ti 47-79 Tungsten W 183.43 Uranium U 237.77 Vanadium... V 50.99 Ytterbium Yt 171.88 Yttrium Y 88.35 Zinc Zn 64.91 89.72 GENERAL INDEX. Absorption of light, 177 in doubly refracting crystals, 178 in isometric crystals, 177 in optically biaxial crystals, 179 in optically uniaxial crystals, 178 Acicular, 144 Acid potassium sulphate, reactions with, 108 Acids, uses of in blowpipe work, 107 results obtained with, 107 Adamantine lustre, 154 Aluminates, 190 Aluminum, minerals of, 321 uses and extraction, 321 , 322 summary of tests, 1 10 see also, 99, 108, 130, 134 Ammonium, minerals of, 297 summary of tests, 1 10 Amorphous, 142 Angle between optic axes, determination, 17s Angle of least deviation, 164 Antiraonides, l8g Antimony, minerals of, 257 uses and extraction, 257 summary of tests, no see also, 97, 98, 102, 107, 125, 128 Apparatus, 86 Arborescent, 144 > Arsenates, 191 Arsenic, minerals of, 255 uses and extraction, 255 summary of tests, in see also, 97, 98, 99, 102, 107, 125, 133 Arsenides, 189 Asterism, 155 Atomic weights, table of, 399 Axes, crystallographic, 5 Axes, interchangeable or equivalent, 6 of the six systems, 6 selection of in each system, 7 Axial angle, measurement, 175 Axial cross, construction, 76 Barium, minerals of, 298 uses of, 298 summary of tests, 112 see also, 99, 130, 133, 135 Basal pinacoid, see pinacoid Basic silicates, 381 Beads, how to make, 88 Bead tests, 103 Beryl formula, calculation, 192 Berzelius lamp, 85 Biaxial crystals, absorption, pleochroism, 179 optical characters, 171 Bismuth, minerals of, 251 uses and extraction, 252 summary of tests, 112 see also, 97, 98, 99, 102, 107, 127, 128 Bismuth-flux, composition, 98 reactions with, 98 Bladed, 143 Blast, method of blowing, ,87 Blowpipe analysis, scheme for, 125 Blowpipe, description of the, 83 care of, 83 Blowpipe lamp, 84, 85 Boracic acid, uses, 109 Boracic acid flux, reactions with, 109 Borates, 190 Borax, action of as flux, 103 reactions with, 104, 105 how to make bead, 88 Boron, minerals of, and their uses, 331 summary of tests, 112 see also, 132, 133 Botryoidal, 143 Brachy dome, see dome pinacoid, see pinacoid pyramid, see pyramid 402 GENERAL INDEX. Braun's solution, 151 Brittle, 146 ' Bromides, 189 Bromine, summary of tests, 112 see also, loi, 108, 131 Bunsen burner as lamp, 84 Cadmium, mineral, 233 use and extraction, 233 summary of tests, 113 see also, 99, 102, 107, 126 Caesium, tests for, 95 Calcium, minerals and their uses, 303 sunmiary of tests, 113 see also, 95, 99, 130, 133, 135 Capillary, 144 Carbon minerals and their uses, 338 Carbonates, 189 Carbon dioxide, summary of tests, 113 see also, loi, 108, 132, 133 Characters of minerals, 137, et seq. Charcoal, method of using, 95 reactions obtained on, 97, 98 forms used, 85 Chart, spectroscopic, 94 Chemical composition of minerals, 187 Chlorides, 189 Chlorine, summary of tests, 113 see also, 108, 113, 131 Chromates, 1 90 Chromium, summary of tests, 113 see also, 102, 105, 129 from chromite, 196 Circularly polarizing uniaxial crystals, i6< Cleavage, 146 Clino dome, see dome pinacoid, see pinacoid prism, see prism pyramid, see pyramid Closed tubes, uses of, 101 reactions in, loi Cobalt, minerals of, 219 uses of, 219 extraction of, 219 summary of tests, 114 see also, 99, 105, 106, 107, 109, 126, 130 Cobalt solution, reaction with, 108 Color, terms used, 155 Coloration of flame, 91 Columbates, 191 Columnar, 142 Composition of minerals, 188 Conductivity of minerals, 184 Copper, minerals of, 263 uses and extraction, 263, 264 summary of tests, 114 see also, 99, 102, 105, 106, 109, 127, 130 Crystal expansion, 181 forms, 8 habit, 9 projection, 76-81 Crystalline aggregates, 142 Crystalline structure, explanation of, I Crystals, classification, 6 circularly polarizing, 169 definition, I determination of optical characters, 168, 174 electrical characters, 183 laws of, 2 magnetic characters, 183 optical characteristics, 164, et seq. positive and negative, 166, 172 thermal characters, 180 Crystals of minerals, 138 curved surfaces, 140 etchings, 140 habit, 138 inclusions, 141 striations, 140 twinning, 139 Crystallography, 1-83 definition, i Cube, 14, 18, 21 Curved surfaces of crystals, 140 Dana' s symbols, 9 Dendritic 144 Dichroism, 124 Dielectric induction, 184 Dihexagonal pyramid, 34 prism, 35, 39 Diploid, 21 Direction of rotation, 170 Ditetragonal prism, 26, 32 pyramid, 25 Dodecahedron, 14, 18, 21 Domes, macro, 50, 51, 63 brachy, 50, 51, 53, 63 GENERAL INDEX. 403 ortho, 56, 57 Double refraction, strength of in uniaxial crystals, 166 Drawing crystals, 76 Drusy, 145 Dull in lustre, 154 Elastic, 146 Electrical charactsrs of crystals, 183 Elements, 189 ' Etching figures, 149 Etchings of crystals, 140 Expansion of crystals, I Si measurement, 181 change of angle, 182 change of optical characters by, 182 Extinction between crossed nicols, 161 Extinction directions, 167, 173 Fibrous, 143 Feel, terms used, 152 Flame colorations, 91 structure of, 87 oxidizing, 87 reducing, 88 Flaming, 106 Fletcher lamp, 85 Flexible, 146 Fluorides, 131 Fluorine, summary of tests, 115 see also, loi, io8, 132 Fluorescence, 155 Foliated, 143 Form, ideal, 8 Form, ideal determination of, II Forms, definition, 8 ^_^ Formula of mineral, determining, 188, 161 Fracture, description of terms, 148 Fuess goniometer, 73 Fuess microscope, l6l Fusibility, scale of, 90 how to test, 90 Fusion, manner of, 91 Gas blowpipe, 84 Geode, I45 Gliding planes, 148 Gold from iron minerals, 196 minerals of, 286 uses and extraction, 286 tests for, 99, 107, 127, 131 Gold, uses of with beads, 106 Goniometers, 72 Granular, 143 Greasy luster, 154 Gypsum plate, 167 Habit of crystals, 138 Hand- goniometers, 72 Hardness, definition and determination, 145 scale of, 145 Heat rays, transmission, 180 Heating power of flame, 88 Heavy liquids, use of, 151 Hemi prism, 63 pyramid, 55 Hemimorphic class, 42, 52 brachy dome, 53 macro dome, 53 pyramid, 43, 53 ditrigonal pyramid, 43 hexagonal pyramid, 43 trigonal pyramid, 43 Hexagonal crystals, optical characters, 165 Hexagonal prism of first order, 35, 37) 45. 46 second order, 35, 37, 39, 43, 45, 46 third order, 37, 46 pyramid of first order, 35, 38 of second order, 36, 37, 39 Hexagonal system, 33-47 axes, 33 classification, 33 definition, 33 drawing axial cross, 78 Hexagonal system, dihexagonal pyramid class symmetry, 33 general form, 33 limit forms, 34 combination, 36 Hexagonal system, hemimorphic class general form, 43 limit forms, 43 combination, 43 Hexagonal system, scalenohedral class symmetry, 39 general form, 39 limit forms, 39 Domes, clino, 56, 57 404 GENERAL INDEX. Hexagonal system, scalenohedral class, combination, 40 Hexagonal system, third order pyramid class symmetry, 37 general form, 37 limit forms, 37 combinations, 38 Hexagonal system, third order rhombohe- dron class, 46 ■general form, 46 limit forms, 46 combinations, 47 Hexagonal system, trapezohedral class, 44 general forms, 44 limit forms, 44 combinations, 45 Hexagonal twins plane a face of a rhombohedron, 68 the basal pinacoid, 68 a face of first order prism, 69 a face of second order prism, 69 Hexahedron or cube, 14, 18, 21 Hextetrahedron, 18 Hexoctahedron, 13. Hydrogen minerals, 337 Hydrous silicates, 383 Hydroxides, 189 Ideal forms, definition, 8 Impalpable, 143 Inclusion of crystals, 141 Incrustation, I45 Index of refraction, 156 of an isometric crystal, 164 uniaxial crystals, 166 biaxial crystals, 172 Indices, 10 Indices of refraction, biaxial crystals, 172 Indium, tests for, 95 Interchangeable axes, 6 Interference between crossed nicols, 161 Interference color as a test, 167, 173 colors with white light, 162 Interference phenomena in optically uniaxial crystals, 166 with convergent light, i68 in optically biaxial crystals, 172 with convergent light, 173 Iodides, 189 Iodine, summary of tests, 115 see also, loi, 108, 131 Iridescence, definition, 155 Iridium minerals, 289 Iridium, uses and extraction, 289 Iron, minerals of, 194 uses of, 194 summary of tests, 116 see also, 99, 102, 105, 107, 109, 126, 128, 130 Isometric crystals optical character, 164 drawing axial cross, 76 Isometric system, 12 axes of, 6, 12 definition, 12 Isometric system, diploid class, 20 general form, 21 limit forms, 21 combination, 21 Isometric system, hexoctahedral class, 12 general form, 13 limit forms, 13, 14 combinations, 16 Isometric system, hextetrahedral class, 18 general form, 18 limit forms, 18 combinations, 19 Isometric twins, 65 plane, an octahedron face, 64 a cube face, 65 a dodecahedron face, 66 Isomorphism, 187 Isotropic crystals, 164 absorption, 177 pleochroism, 177 Jolly's balance, use of, 151 Klein's solution, 151 Lamellar, 143 Lamp, the blowpipe, 84, 85 oils used in, 85 Laws of crystals, 2 of constancy of interfacial angles, 2 of symmetry, 3 of simple mathematical ratio, 8 Lead, minerals of, 241 uses and extraction, 241 summary of tests, n6 see also, 97, 98, 99, 102, 107, 109; 127, 128 GENERAL INDEX. 40s Lead, uses of with beads, loS Lithium, summary of tests, 117 see also, 95, 109, 133 Lustre, definition, 154 description of terms, 154 Macro dome, see dome pinacoid, see pinacoid pyramid, see pyramid Magnesium, minerals of and their uses, 317 summary of tests, 1 17 see also, 99, 108, 130, 134 Magnesium ribbon, tests with, 108 Magnetic characters of crystals, 183 Malleable, I46 Mammillary, 144 Manganese, minerals of, 214 uses of, 214 summary of tests, 117 see also, 105, 107, 109, 129 Massive, 142 Mattrasses, see closed tubes Measurement of crystal angles, 72 Mercury, minerals of, 276 uses and extraction, 276 summary of tests, 118 see also, 98, 102, 107, 128, 133 Metallic lustre, 154 Metasilicates, 357 Micaceous, 143 Mica plate, 167 wedge, 167 Microscope, polarizing, i5l Fuess, i6i Miller's symbols, 9 Minerals, distinctions of, 137 characters of, 137, et seq. tables, 397 Mineralogy, definition, 137 Miscellaneous apparatus, 86 Moh's scale of hardness, 144 Molybdates, 190 Molybdenum, minerals of, 261 uses, 262 summary of tests, 118 see also, 97, 98, 99, 105, 107, 129, 133 Monoclinic crystals optical characters, 171 distinctions, 176 drawing axial cross, 77 Monoclinic system, 55 axes of, 6, 55 definition, 55 Monoclinic system, prismatic class, 55 general form, 55 limit forms, 56, 57 combinations, 58 Monoclinic twins, 70 plane, the ortho-pinacoid, 70 basal pinacoid, 70 a dome face, 70 Negative crystals, uniaxial, 166 biaxial, 172 Nickel, minerals of, 222 uses of, 222 extraction of, 222 summary of tests, 119 see also, 99, 105, 106, 107, 109, 126, 129 Nitrates, 189 Nitric acid, summary of tests, 119 see also, 131 Nodular, 143 Non-metallic lustre, 154 Normal incidence, 157 Notation, methods of, 9 Octahedron, 15, 2 1 Odors in closed tubes, loi in open tubes, 103 terms used, 153 Oils used in lamps, 85 Oolitic, 144 Opalescence, 155 Opaque, 156 Open tubes, uses of, 102 reactions in, 103 Optic axes, determination of angle, 175 Optic axis, uniaxial, 165 biaxial, 171 Optical characters, 154 determination, 1 68 Optical characteristics, 164, et seq. Optical distinctions, 176 Optical principal sections, uniaxial, 165 biaxial, 171 Optically isotropic crystals, 164 uniaxial crystals, 1 65 biaxial crystals, 171 4o6 GENERAL INDEX. Ortho dome, see dome pinacoid, see pinacoid prism, see prism pyramid, see pyramid Orthorhombic crystals optical characters, 171 distinctions, 176 drawing axial cross, 77 Orthorhombic system, 48 definition, 48 axes in, 6, 48 series, 48 selection'of unit plane, 48 Orthorhombic system, hemimorphic class, general form, 53 limit forms, 53 combinations, 53 Orthorhombic system, pyramidal class, 49 general form, 49 limit forms, 50 combinations, 52 Orthorhombic twins, 69 plane, a prism face, 69 a dome face, 69 a pyramid face, 69 Orthosilicates, 367 Oxidation by means of blowpipe, 88 Oxides, 189 Oxidizing flame, 87, 88 Parameters, 9 Parting, 149 Pearly lustre, 154 Penfield's solution, 151 Percussion figures, 149 Phosphates, 1 90 Phosphorescence, 155 Phosphorus, summary of tests, 119 see also, 108, 132 Physical characters of minerals, 137 Piezoelectricity, 186 Pinacoid, basal, 26, 30, 31, 35, 37, 39 45, 46, 57, 62 brachy, 50, 51, 63 Pinacoid, clino, 56, 57 macro, 50, 63 ortho, 56, 57 Pisolitic, 144 Plane, basal, 43, 53 Plane of polarized light, 159 Planes of symmetry, J of vibration, 158 Plaster tablets, methods of use, 96 reactions obtained on, 97, 98 preparation, 85 Platinum minerals, 289 Platinum production, 289 Play of color, 155 Pleochroism, 177 in optically uniaxial crystals, 178 in biaxial crystals, 179 Plumose, 144 Polariscope, description and use for parallel light, 160 for convergent light, 163 Polarized light, 159 Polysilicates, 351 Positive crystals, uniaxial, 166 biaxial, 172 Potassium, minerals of, 291 uses, 291 summary of tests, 119 see also, 95, 133, 135 Potassium chlorate, reactions with, 109 bisulphate, 108 Principal sections, optical uniaxial, 165 biaxial, 171 Principal vibration directions, 171 Prism, brachy, 50, 51 clino, 58 dihexagonal, 35, 39 ditetragonal, 26, 32 ditrigonal, 43, 45 hemi, 63 macro, 50, 51 of first order, 26-31 of second order, 26, 30, 31 of third order, 30 ortho, 58 rhombic, 53 trigonal, 39, 43 unit, 50, 51, 58 Pyramid clino, 56 dihexagonal, 34 ditetragonal, 25 hemi, 55 of first order, 27, 30 of second order, 27, 30, 32 GENERAL INDEX. 407 Pyramid, of third order, 37 ortho, 56 trigonal, 45 unit series, 56 Pyramid, hemimorphic, 53 ditrigonal, 43 hexagonal, 43 trigonal, 43 Pyritohedron, 21 Pyroelectricity, 185 Quarter undulation mica plate, 1 67 Quartz wedge, 167 Radiating, 145 Reducing flame, 88, 89 Reduction, 88 Reduction color tests, 106 Reflection, total, 157 Reflection goniometers, 72 Refraction, definition, 156 double, 158 index of, 156 in plane parallel plates, 157 principal indices of biaxial crystals, 172 Reniform, 143 Resinous luster, 154 Reticulated, 144 Rhombic prisms, 53 Rhombohedron of the first order, 40, 45, 46 of second order, 47 of third order, 46 Rock, definition 138 Rotation, direction of, 170 Rubidium, tests for, 95 Salt of phosphorus, action of as flux, 104 reactions with, 105 bead, how to make, 88 Scale of hardness, Moh's, 145 fusibility, v. Kobell's, go Scalenohedron, hexagonal, 39 tetragonal, 30 Schemes for blowpipe analysis, 125 for determination of minerals, 396 Sclerometer, 146 Sectile, 147 Selenides, 189 Selenium, summary of tests, 120 see also, 97, 98, 99, 102, 127 Sheaf like, 144 Silica, 342 Silicates, and their uses, 342 Silicates, 191 Silicon, summary of tests, 120 see also, 99, 130 Silky lustre, 154 Silver, minerals of, 278 uses and extraction, 278 summary of tests, 120 see also, 99, 107, 127, 131 Simple mathematical ratio, law of, 8 Soda, action of as flux, 98 reactions with, 99 Sodium, minerals of, 293 reactions with, 100 uses, 293 summary of tests, 121 see also, 95, 133 Sodium thiosulphate, method of using, 107 reactions with, 107 Specific gravity determination, 150 Spectroscope, use of, 92 description, 93 chart, 94 Sphenoid, tetragonal, 32 Stalactitic, 144 Streak, definition and determination, 155 Striations of crystals, 140 Strontium, minerals of and their uses, 300 summary of tests, 121 see also, 99, 130, 133, 13S Sublimates in closed tubes, loi in open tubes, 103 on charcoal, 97 on plaster, 97 Submetallic, etc. , see metallic, etc. Subsilicates, 381 Sulphates, 190 Sulphides, 189 Sulphur minerals, 335 Sulphur extraction, 335 summary of tests, 121 see also, 102, 127 Summary of blowpipe tests, no Surface conductivity, 180 Symbols of Weiss, Dana, and Miller, 9 Symmetry, definition of, 3 planes of, 5 law of, 3 4o8 GENERAL INDEX. Symmetry, trae structural, 5 Systems, the six crystal, 6 axes of, 9 classes of, S determinations of, 7 Tables for mineral determination, 320 Tarnish, definition, 155 Taste, terms used, 153 Tellurides, 189 Tellurium minerals, 335 summary of tests, 121 see also, 98, 99, 102, 127 Tenacity, description of term, 146 Tetragonal crystals optical characters, 165 drawing axial cross, 77 Tetragonal prisms of 1st order, 26 prisms of 2d order, 26 pyramid of 2d order, 27 sphenoid, 32 trisoctahedron, 15, 21 tristetrahedron, 19 Tetragonal system, definition, 23 axes, 6, 23 classification, 23 Tetragonal system, ditetragonal pyramid class, 24. symmetry of, 24 general form, 25 limit forms, 25 series and combinations, 27 Tetragonal system, scalenohedral class, 31 general form, 31 limit forms, 31 series and combinations, 32 Tetragonal system, third order pyramid class, 29 general form, 30 limit forms, 30 series and combinations, 30 Tetragonal twins, 67 Tetrahedron, 18 Tetrahexahedron, 14, i8 Tetrapyramid, 62 Thallium, tests for, 95 Thermal characters, 180 Thermo-electricity, 184 Thorium, minerals of, 239 uses of, 239 Thoulet solution, 151 Tin, minerals of, 234 uses and extraction, 234 summary of tests, 122 see also, 97, 98, 99, 102, 107, 108, 126, 127, 130 uses with fluxes, I06 uses in color tests, 106 Titanium, minerals of, 236 uses, 236 summary of tests, 122 see also, 105, 107, 108, 128, 130, 134 Titano-silicates, 395 Total reflection, 157 Translucency, definition and forms, 156 Transparent, 156 Trapezohedron, trigonal, 44 Tricliuic crystals optical character, 171 distinction, 176 drawing axial cross, 77 Triclinic system, definition, 6, 61 axes, 61 series, 61 Triclinic systepi, pinacoidal class, 61 general form, 62 limit forms, 62 combinations, 63 Triclinic twins, 70 Trigonal prism, see prism pyramid, see pyramid trapezohedron, 44 trisoctahedron, 15, 21 tristetrahedron, 19 Tube tests, loi, 102 Tungstates, 190 Tungsten, summary of tests, 122 see also, 99, 105, 107, 128 from wolframite, 196 Twin crystals drawing of, 81 Twinning crystals, 65-71, 139 definition, 65 plane, 65 axis, 65 Twins, 65 hexagonal, 68, isometric, 65 monoclinic, 70 orthorhombic, 69 tetragonal, 67 triclinic, 70 GENERAL INDEX. 409 Types, 189 Uniaxial crystals, optical characters, 165 absorption, 1 78 pleochroism, 1 78 Unit prism, 50, 51, 58 pyramid, 56 Uranium, minerals of, 260 uses, 260 summary of tests, 123 see also, 105, 107, 129 Vanadinates, 191 Vanadium, summary of tests, 1 23 see also, 99, 105, 107, 129 Vibration, directions, 171 Vibrations, planes of, 158 Vitreous lustre, 154 Volatilization, elements affected, 95 Water, tests for, loi, 133 Weiss' s symbols, 9 Westphal's balance, use of, 152 Zeolites, 384 Zinc, minerals of, 228 use of, 228 extraction of, 228 summary of tests, 123 see also, 97, 99, 102, 107, 108, 126 INDEX TO MINERALS Acmite, 360 Aegirite, 360 Actinolite, 364 Adamantine spar, 324 Adularia, 354 Agate, 346, 348 AgoUte, 392 Aikinite, 253 Alabandite, 214 Alabaster, 306, 307 Albite, 354 Alexandrite, 330 AUanite, 380 Almandite, 370 Aluminite, 327 Alum stone, 328 Alunite, 327 Alunogen, 328 Amalgam, 280 Amazonsttjne, 354 Amber, 339 Amber mica, 389 Amethyst, 348 Amphibole, 363 Analcite, 385 Anatase, 238 Andalusite, 377 Andradite, 370 Anglesite, 245 Anhydrite, 305 Ankerite, 316 Annabergit?, 225 Anorthite, 356 Anorthoclase, 354 Antimony, 258 Apatite, 308 Aphthitalite, 291 Apophyllite, 384 Aquamarine, 365 Aragonite, 310 Argentine, 313 Argentite, 280 Aragonite, 310 Arsenic, 255 Arsenoltte, 257 Arsenopyrite, 200 Asbestua, 345, 364 Asparagus stone, 308 Asphaltum, 339 Atacamite, 272 Augite, 358, 360 Autunite, 261 Aventurine, 348 Axinite, 380 Azurite, 274 Balas ruby, 319, 320 Barite, 298 Barytocalcite, 300 Bastite, 358 Bauxite, 326 Beryl, 365 Biotite, 389 Bismite* 254 Bismuth, 252 Bismuth ochre, 254 Bismuthinite, 253 Bismutite, 254 Black hematite, 217 jack, 228 lead, 341 mica, 389 oxide of copper, 271 oxide of manganese, 216 Blende, 228 Bloodstone, 349 Blue carbonate of copper, 274 iron earth, 209 stone, 344 vitrol, 272 Bog iron ore, 207 manganese, 217 Boracite, 334 Borax, 332 Bornite, 267 Boronatrocalcite, 332 Bort, 341 Bournonite, 243 Braunite, 215 Brimstone, 335 Brittle silver ore, 283 Brochantite, 272 Bromargyrite, 285 Bromyrite, 285 Bronzite, 358 Brookite. 238 Brown clay ironstone, 208 hematite, 207 Brucite, 318 Calamine, 231 Calaverite, 289 Calc spar, 311 Calcite, 311 Calomel, 277 Cancrinite, 368 Capillary pyrites, 223 Carbonado, 341 Carnelian, 349 Cassiterlte, 235 Cat's-eye, 330, 348 Celestite, 300 Cerargyrite, 284 Cerussite, 247 Ceylonite, 320 Chabazite, 385 Chalcanthite, 272 Chalcedony, 346, 348 Chalcocite, 266 Chalcopyrlte, 267 Chalk, 313 Chesterlite, 354 Chiastolite, 377, 391 Chili saltpetre, 296 China clay, 394 Chloanthite, 225 Chondrodite, 381 Chromic iron, 211 Chromite, 211 Chrysoberyl, 330 Chrysocolla, 274 Chrysolite, 371 Chry sop rase, 349 Chrysotile, 345 Cinnabar, 277 Clausthalite, 244 Clay ironstone, 205 Clinochiore, 390 Coal, mineral, 338 Cobalt glance, 220 pyrites, 219 CobaltitCt 220 Colemanite, 333 Columbite, 212 Copiapite, 208 Copper, 265 Copper glance, 266 Copper nickel, 224 pyrites, 267 uranite, 261 vitriol, 272 Copperas, 209 Cordierite, 367 412 INDEX TO MINERALS. Corundum, 324 Crocidolite^ 365 Crocoite, 249 Cryolite, 323 Cube ore, 210 Cuprite, 270 Cyanite, 366 Cymophane, 330 Dark ruby silver, 282 Datolite, 378 Descloizite, 250 Desmine, 385 Diallage, 360 Diamond, 338, 340 Diaspore, 326 Dichroite, 367 Diopside, 360 Dioptape, 275 Dog-tooth spar, 313 Dolomite, 314 Dry-bone, 230 Edenite, 364 Eisstein, 323 ElEeolite, 367 Electric calamine, 231 Embolite, 285 Emerald, 365, 366 Emerald nickel, 225 Emery, 324 Enargite, 26S £nstatite,358 Epidote, 379 Epsomite, 318 Epsom salt, 318 Erythrite, 221 False topaz, 348 Fay all te, 372 Feather ore, 244 Feldspar, 352 Felsite, 354 Fibrolite, 377 Fiorite, 351 Ferruginous quartz, 348 Fire opal, 351 Flint, 349 Flos ferri, 310 Fluorite, 304 Fluor spar, 304 Fontainbleau sandstone, 313 Fool's gold, 197 Franklinite, 203 French chalk, 392 Fullers earth, 346 Galena, 242 Galenite, 242 Garnet, 369 Garnierite, 226 Gay-Lussite, 297 Geyserite, 351 Gibbsite, 326 Glauber salt, 296 Glauberite, 295 Glaucophane, 365 Goethite, 207 Gold, 287 Goshenite, 366 Goslarite, 229 Graphic tellurium, 288 Graphite, 338, 341 Gray antimony, 258 copper ore, 269 Greasy quartz, 348 Green ockite, 233 Green carbonate of copper, 273 Grossularite, 370 Guano, 309 Gypsum, 306 Halite, 294 Hausmannite, 215 Hauynite, 368 Heavy spar, 298 Hedenbergite, 360 Heliotrope, 349 Hematite. 204 Hessite, 281 Heulandite, 385 Hiddenite, 361 Hornblende, 363, 364 Horn silver^ 284 mercury, 277 Horse flesh ore, 267 Hyacinth, 374 Hyalite, 351 Hyalosiderite, 372 Hydraulic limestone, 313 Hydrozincite, 230 Hydrohematite, 207 Hypersthene, 358 Ice, 337 Iceland spar, 311, 313 Idocrase, 373 Ilmenite, 206 Indianite, 356 Infusorial earth, 344, 351 lodargyrite, 285 lodyrite, 285 lolite, 367 Iridosmine, 290 Iron, 196 Iron pyrites, 197 Isinglass, 388 Jade, 364 Jadeite^ 361 Jamesonite, 244 Jasper, 346 Kainite, 292 Kalinite, 292 Kaolin, 394 Kaolinite, 394 Kermesite, 259 Krennerite, 289 Kyanite, 366 Labradorite, 356 Lapis Lazuli, 369 Lazulite. 329 Lazurite, 369 Lead, 242 Lepidolite, 390 Leucite, 357 Leucopyrite, 202 Libethenite, 272 Light ruby silver, 281 Lime feldspar, 356 soda feldspar, 356 uranate, 261 Limestone, 311, 313 Limonite, 207 Linarite, 246 Linnaeite, 219 Lithia mica, 390 Lithographic limestone, 313 Lodestone, 202 Lollingite, 202 Loxoclase, 354 Magnesian limestone, 314 mica, 389 Magnesite, 319 Magnetic iron ore, 202 Magnetic pyrites, 197 Magnetite, 202 Malachite, 273 Malacolite, 360 Manganblende, 214 Manganite, 216 Marble, 311, 313 Marl, 313 Marcasite, 199 Martite, 205 Mascagnite, 297 Meerschaum, 393 Melaconite, 271 Melanterite, 209 Melilite, 374 Menaccanite, 206 Mercury, 276 Mica, 345 Microcline, 354 Milky quartz, 348 Millerite, 223 Mimetite, 247 Mineral coal, 338 Minium, 244 Mirabilite, 296 Mispickel, 200 Misy, 208 Molybdenite, 262 Molybdite, 262 Monazite, 240 Mundic, 197 INDEX TO MINERALS. 413 Muscovite, 388 Native antimony, 258 arsenic, 255 boracic acid, 331 bismuth^ 252 copper, 265 g-old, 287 iron, 196 lead, 242 mercury, 276 platinum, 290 silver, 279 sulphur, 335 tellurium, 337 ultramarine, 369 vermilion, 277 NatroHte, 387 Needle ore, 253 Nephelile, 367 Nephrite, 364 Niccolite, 224 Nickel bloom, 225 Nigrine, 237 Nitre, 292 Noselite, 36B Noumeite, 226 Ochre, red, 205 yellow, 208 Octahedrite, 23B Ollgoclase, 355 Olivenite, 273 Olivine, 371 Onyx, 313, 349 Opal, 350 jasper, 351 Orangite, 240 Orpiment, 256 Orthoclase, 352 Osteolite, 309 Ozocerite, 339 Pandermite, 333 Pearl sinter, 351 Pearl spar, 314 Pectolite, 362 Pencil-stone, 395 Pentlandite, 224 Peridot, 371 PericlJne, 354 Perovskite, 317 Perthite, 354 Petalite, 352 Petroleum, 339 Pharmacolite, 310 Pharmacosiderite, 210 Phenacite, 372 Phlogopite, 390 Phosgsnite, 248 Phosphate rock, 308 Phosphorite, 309 Picotite, 320 Pitchblende, 260 Plasma, 349 Platinum, 290 Plumbago, 341 Plumbocalcite, 314 Polybasite, 284 Potash alum, 292 feldspar, 352 mica, 3S8 Prase, 349 Precious opal, 351 garnet, 370 Prehnite, 380 Priceite, 333 Prochlorite, 391 Proustite, 281 Psilomelane, 217 Purple copper ore, 267 Pyrargyrite, 282 Pyrite, 197 Pyrolusite, 216 Pyromorphite, 246 Pyrope, 370 PyrophylHte, 395 Pyroxene, 358 Pyrrhotite, 197 Quartz, 346 Realgar, 256 Red antimony, 259 hematite, 205 iron ore 204 ochre, 205 oxide of copper, 270 silver ore, 281 zinc ore, 229 Rensselaerite, 392 Rhodochrosite, 218 Rhodonite, 362 Rhyacolite, 354 Ripidolite, 391 Rock crystal, 34S gypsum, 307 meal. 314 salt, 294 Rose quartz, 348 Ruby, 324 copper, 270 spinel, 319 silver, 281, 282 Rutile, 237 Sal ammoniac, 297 Salt, 294 Saltpetre, 292 Sandstone, 344, 349 Sanidin, 354 Sapphire, 324 Sard, 349 Sardonyx, 349 Sassolite, 331 Satin-spar, 307, 313 Scapolite, 372 Scheelite, 316 Schorl, 381 Scorodite, 210 Selenite, 306, 307 Semi opal, 351 Sanarmontite. 260 Sepiolite, 393 Serpentine, 392 Siderite, 210 Siliceous sinter, 351 Sillimanite, 377 Silver, 279 Silver glance, 280 Slate, 344 Smaitite, 221 Smithsonile, 230 Smoky quartz, 348 Snow, 337 Soapstone, 391 Soda feldspar, 354 lime feldspar, 355 Soda nitre, 296 Sodalite, 368 Spartaite, 314 Spathic iron, 210 Specular iron, 204 Spessartite, 370 Sphalerite, 228 Sphene, 394 Spinel, 319 Spodumene, 360 Stalactite, 313 Stalagmite, 313 Stannite, 235 Stassfurtite, 334 Staurolite, 382 Steatite, 392 Stephanite, 283 Stibnite, 258 Stilbite, 385 Stolzite, 251 Ftream tin, 235 Stromeyerite, z8i Strontianite, 302 Succinite, 339 Sulphur, 335 Sylvanite, 288 Sylvite, 291 Talc, 344. 392 Tantalite, 212 Tellurium, 337 Tennantite, 268 Tenorite, 271 Tetradymite, 254 Tetrahedrite, 269 Thenardite, 295 Thomsonite, 387 Thorite, 240 Thulite, 379 Tin stone, 235 414 INDEX TO MINERALS. Tin pyrites, 235 Tinkal, 332 Titanic iron ore, 206 Titanite, 395 Topaz, 375 Torbernite, 261 Touchstone, 349 Tourmaline, 381 Travertine, 313 Tremolite, 364 Tridymite, 350 Triphylite, 209 Triplite, 218 Tripolite, 351 Trona, 296 Troostite, 231 Turgite, 207 Turquois, 328 Ulexite, 333 Umber, 208 Uralite, 365 Uraninite, 260 Uvarovite, 370 Urao, 296 Valentinite, 260 Vanadinite, 249 Verd-antique, 391 Vesuvianite, 373 Vivianite, 2c^ Wad, 217 Water, 337 Wavellite, 329 W^ernerite, 372 White iron pyrites, 199 lead ore, 247 mica, 388 W^illemite, 231 Witherite, 299 Wolframite, 212 Wollastonite, 361 Wood-opal, 351 Wood tin, 235 Wulfenite, 250 Yellow copper ore, 267 Yellow ochre, 208 Yellow quartz, 348 Zaratite, 225 Zinc blende, 228 vitriol, 229 bloom, 230 Zincite, 229 Zircon, 374 Zoisite, 379 Tbe "Moses" Economic Mineral Collections These collections are especially prepared to illustrate this book, and are modeled after those used by Prof. Moses at Columbia University. Sample collections were submitted to him and any changes which he regarded as desirable were made. The particular purpose of these collections is to show the ordinary varieties of the com- mon and, more especially, the economically important species. »' Moses" Economic Collection, No. 1, includes 216 specimens, averaging 2 X 2]/^ inches, each numbered to correspond with complete printed label, giving species, variety, crystal system, chemical formula and locality. Price, packed ready for ship- ment, $60.00. Weight, about 120 pounds. "Moses" Economic Collection, No. 2, includes 216 specimens, averaging I X l)^ inches, put up in six well made wooden collection boxes, each specimen being in a separate pasteboard tray and labeled the same as Collection No. i. Price com- plete, the six boxes packed in one case ready for shipment, $18.00. Weight, about 35 pounds. "Moses" Economic Collection, No. 3, includes 216 specimens, averaging 1^ X ^-inch, put up in a well made wooden partitioned collection box, each specimen being numbered to correspond with accompanying label list. Price complete, packed ready for shipment, $8.00. Weight, about 7 pounds. Other Mineral Collections. In addition to the foregoing we put up many other scientific collections, illustrating other books, at prices ranging from 75 cents to $1,000.00. For descriptions see our price lists. Minerals for Laboratory Examination. We sell over 300 different minerals by weight at very low prices. The great economy of purchasing by weight minerals needed in the laboratory is now generally recognized. Send for our latest complete lists of these minerals. Loose Crystals. We have many thousands of detached crystals in stock, and sell them either singly or in collections, noting the forms shown by each crystal. Gonionneters. Prof. Penfield's excellent pocket goniometers, described in the Mineral Collector for September, 1900, are unquestionably the cheapest, most accurate, and convenient hand goniometers ever invented. 50 cents each, postpaid. We also have excellent brass foniometers, similar to those in use at Columbia and other leading Universities, at 6.75 each, in neat leather case. Crystal Stands. We carry a full stock of various kinds of hard-wood crystal stands, either ebonized, japanned, or in natural-wood finish. Also brass crystal holders. Send for descriptive circulars. Our Store Occupies the entire top floor, 4000 square feet, of a modern building, and is admir- ably lighted on three sides by sixteen windows. Visitors are always cordially welcome.. Take either Eighth Avenue cars to Jane Street, Ninth Avenue L to 14th Street, or Fourteenth Street cars to Ninth Avenue. Complete Illustrated Catalogue, giving crystallographic system, hardness, specific gravity, chemical composition and formula of every mineral, and much other valuable information, 25 cents in paper, 50 cents in cloth. Illustrated Price-Lists, Bulletins and Circulars Free. Geo. L. English & Co., MINERALOGISTS, 812 and 814 Greenwich St. (S.W. Cor. Jane St.), New York City. F. YI. Devoe & Co., ARTISTS' MATERIALS, Mathematical Instruments, Fine Varnishes, House Paints, New York. Chicago. ESTABLISHED 1866. INCORPORATED 1888. HENRY HEIL CHEMICAL CO., Nos. 208-212 South Fourth Street, ST. LOUIS, MO., Manufacturers and Importers of Chemicals and Chemical Apparatus, Laboratory Supplies and Assay and Blow-Pipe Apparatus and Materials. All and eveiytbing the Chemist and Assayei needs can be found at our Establishment. We guarantee best quality and lowest prices. Our catalogues cover over 500 pages and contain 3000 illustrations. The Roessler & Hasslacher chemical CO., 100 William Street, New York, Cyanide of Potassium Bleach (Chloride of Lime), Hyposulphite of Sodium, Peroxide of Sodium, Sulphide of Iron, and Other Chemicals. Dixon's Black Lead Crucibles. Black Lead (Graphite) Crucibles ■were first made by Joseph Dixon in 1827. They at once became the standard at home and abroad, and are to-day still the standard. They are made in sizes iirom X-Ponnd to 1,000 pounds capacity Specially prepared Crucibles for melting different metals. All inquiries concerning Crucibles or Grraphite gladly answered. Joseph Dixon Crucible Co., Jersey City, N. J., U.S. A. The Orford Copper Co. Robert m. Thompson, President, 99 JOHN STREET, ^EW YORK, Copper and Nickel Smelters Works at Constable's Hook, N. J., Opposite New Brighton, Staten Island. Copper and Nickel Ore, Mattes or Bullion Purchased. Advances Made on Consignments for Refining and Sale. SPECIALTY MADE OF Silver-Bearing Ores and Mattes^ Copper Ingfots, Wire Bars and Cakes. MALLEABLE NICKEL SHOT, PLATES, INGOTS, BARS, SHEETS, WIRE. Best Quality for Anodes, German-Silver and Nickel Steel for ARMOR PLATES. GENERAL ELECTRIC COMPANY'S X-Ray Apparatus For Direct and Alternating Current. CROOKES' TUBES, with New Adjusters, For all classes of work. FLUOROSCOPES, with Barium Screens, In all sizes. DEWAR BULBS for Liquid Air. ARE ALL STANDARD. Send for Catalogue 9050. X-Ray Tube with Vacuum Regulator. Edison Decorative and miniature Lamp Department, Harrison, N. J. Christian Becker, Successor to BECKER & SONS and to BECKER BROS. MANUFACTURER OF Balances and Weights of Precision for Assayers, Chemists, Jewelers and all who require accuracy of weight. In use in all colleges and in the scientific department of the U. S. Government. ONLY FACTORY: NEW ROCHELLE, N. Y. OFFICE: 7 MAIDEN LANE, NEW YORK QTY. ILLUSTRATED PRICE LIST ON APPUCATION. SPON & CHAMBERLAIN. THOMPSON Polyphase Electric Currents and Alternate Current »Io= tors, being the new authorized revised and enlarged edition, with 24 illustrations in colors, 8 large folding plates and over 500 pp. of text. 8vo, cloth, $5.00j BAYLEY. — Chemists' Pocketbook. Seventh Edition, revised and enlarged, a pocketbook for Chemists, Manufacturers, Metallurgists, Students, etc. 32mo, roan, gilt, $2.00 ALLEN, Prof. C. F Railway Curves and Earthwork. A Text-Book for Students in Railway Engineering. Limp leather, . $2.00j CORDEIRO, Dr. J. F. B.— Barometrical Determination of Heights. A practical work for Surveyors and Mountain Climbers. Limp leather, $1.00 Publishers of Books in all branchis of Engineering. 12 CORTLANDT ST., NEW YORK, U.S.A. RICKETTS & BANKS, 104 JOHN STREET, NEW YORK. ORES TESTED. 8®» Complete Ore Milling and Testing Works for making practical working tests of ores to determine the Best Method of Treatment. Milling, Metallurgical and Chemical Processes investigated. ASSAYS and ANALYSES. Assayers by appointment to New York Metal Mxcbange, Established 1870. S. HAWKRIDGE, MANUFACTURER OF ill Also to illustrate Mayer &* Barnard' s Book on "Light" Mayer's Book on "Sound." ^■^L Blowpipe Analysis cciumHa"umvc„ity. At the Stevens Institate of Technology, River Street, above Fifth., Catalogues sent on application. HOBOKEN, N# /♦ AWARDS OF MERIT. Silver Medal, American Institute, 1875. Bronze Medal, American Institute, 1875. Two Silver Medals, Cincinnati Exposition. College Lanterns. Stereopticons, Accessories and Supplies. Magnesium Lamps and Flash Pistols. Magnesium Ribbon and Powder. MINERALOGY. In this department we have long made a specialty of compiling systematic collections of various scope and value to illustrate the numerous text-books and manuals on thi.s subject. Our systematic collections of minerals range in price from JS5.00 to $250 00, depending upon the size, number and quality of the specimens, but m each instance however, the specimens are thoroughly typical We will at all times be glad to give estimates on collections of various sizes to illustrate this work. Our stock of minerals is large, and consists of choice material, in specimens from the size of those in the student's collection to large museam specimens, which are soid separately as well as in collections. As an adjunct we have numerous sets of crystal models for the study of Crystallography. (Send for circulars and caialogaes.) Ward's Natural Science Establishment, 30-40 College Avenue, Rochester, N. Y. (Mineralogy, Geology, Paleontology, ZoSlogy, Human Skeletons and Anatomical Models, Archie ology and Ethnography.) CHARACTERS OF CRYSTALS An Introduction to Physical Crystallography, By ALFRED J. MOSES, E.M., Ph.D., Professor of Mineralogy, Columbia University. "Tliis is the first American text-book on purely physical crystallography, and contains the principles of modern crystallography and descriptions of the instruments and methods used in the determination of the various physical characters of crystals. The advanced students in mineralogy and crystallography WvW find it of much assist- ance, because it presents in a concise form, omitting unnecessary detail, the subjects treated of in the larger foreign text- books on physical crystallography." 211 Pages, 321 Figures. Price, $2.00. New York : D. Van Nostrand Company FooTE Mineral Co., (formerly dr. «. E. FOOTE.) WARREN M. FOOTE, Manager. Established 1876. PHILADELPHIA : PARIS : 1317 Arch Street. 24 Rue du Charap=de=Mars. Minerals. Cabinet and Museum Specimens, Educational Collections, Laboratory Material. TO ILLUSTRATE THIS BOOK we prepare sets in two sizes, in- cluding 232 minerals, the names of which appear in heavy type in the index. Omitting 57 of the rarer and more expensive, we furnish the important ones, numbering 175, at the following prices: 175 Specimens, averaging I J4^ X i^ inches, . . . $14.00 175 Specimens, averaging 2x2)^ inches, .... 28.00 The 57 mentioned above as omitted are supplied for $16.00 and §32.00, in their respective sizes. Neat quartered oak cotnpanmem cabinet to accompany the first set, containing divisions for i8o specimens, 92.40. Pasteboard irays to hold the larger collection can be furnished at the rate of Ji.oo per hundred. Care is exercised by experienced assistants to select good character- istic examples of "standard" quality, crystallized when practicable, and neatly trimmed, all are accurately labelled. Collection No. 20. Contains 120 specimens, averaging 2x2)^, and is arranged to accompany Prof Dana's " Minerals and How to Study Them.'" It answers the requirements of other elementary works in a satisfactory manner or can be used as a beginners' reference set. Price, $15.00. Collection No. 21. Same as above, in smaller size, specimens aver- aging i^ inches square. Price, $7.50. (Quartered oak compartment cabinet, §1.60 additional. ) Collection No. 16. 180 specimens, averaging 1 J^ inches square, selected as best adapted for practical study and reference. Price, $12.50. (Compartment cabinet, quartered odk, $2.40. ) Collection No. 27. "Metallurgical." 200 specimens, averaging 2x2^ inches, embracing all the more important ores of common, rare or precious metals. Price, $75.00. COMPLETE MINERAL CATALOG. I^ast Mdition. Contains Dana's Abridged Classification, Alphabetical Arrangement of Mineral Names, New Species, Metallurgical Classification, etc. , etc. Paper Bound, 25c.; Cloth Bound, 50c. ^^'Illustrated Collection and Supplementary Catalogs mailed free on application. Minerals Purchased. Specimens Identified. "Send us a trial order!" ■ .i ,„:,yyy '/-,< . ..