y? 0..e CORNELL UNIVERSITY LIBRARY Cornell University Library QE 376.W18 Mineralogy of the H. B. Mine, Saimo, B 3 1924 003 975 855 UNIVERSITY OF TORONTO STUDIES GEOLOGICAL SERIES No. lo: MINERALOGY OF THE H.B. MINE, SALMO, B.C., BY T. L. Walker THE UNIVERSITY LIBRARY: PUBLISHED BY THE LIBRARIAN, 1918 cv ^^ o\ver under the nr.cro>cope it is seen that almost all the [iieees lie wil h the best elea\'a|^e parallel to the glass support. The other cleavages as obser\ eil on these fragments appear to be at right angles to one another, so that the mineral seems to be in agreement with the rhombic s\ stem. Th.il the filates are almusl all of a common crystallographic orientation is shown b>' the fact that they show, when examined in con\'ergent light, a biaxial interference-figure. Such cleawige-ijlates can fte also rcadil>" distinguished Irctm the small Tiumber tollowmg one of the other cleavages, because the former exhibit \er\' low birelringeiice as compared witii the latter. (Di'Tic \L Propfrties "The mineral is too clea\able to make it i)Ossiblc to cut j:)risms to determine the indices of refraction. An attempt was made to find these constants by total reflection, using thin plates parallel to the best clea\"age Since these plates give good interlerence-figures, the acute lasectrix is apparent l>' normal to this cleavage. Fig. 3 loK- -t Micro-sections of Spenccrite ^liuwinu lametlar twinnin;;. Owiii.g to the smallncss (jl the cleavage-plates and slight lark ol parallelism ot different parts of a single ])late the results were v-ery unsatisl.iclor>-. The wdue for /j for sodium-light is about I 609; 1 he optic angle lur sodium-liglu was measured on the a.xial angle apparatus of Fuess, using miinofjromonaphthaleiie instead of oil: 2l-iy = 46° 26', hence 2Ey = v. Crystallization . "In general, the optical and physical properties above mentioned seem to suggest that the mineral is rhombic in crystallization. This is not the case however, as shown by the following: hird Cleovnge- 00 Secor Cleavaae 6 6' Crystallographic scheme of Spencerite. (a) A thin section cut more or less at right angles to the best cleavage shows that the mineral is polysynthetically twinned with an extinction-angle of about 6°. The plates of the twin complex are parallel to the best cleavage. (Figs. 3 and 4.) (b) By etching with cold, one per cent, nitric acid for five minutes, very definite etch-figures are obtained on the best cleavage. These figures are sym- metrical about only one plane (the second best cleavage), and consequently the best cleavage does not correspond to a pinacoidal cleavage in a holohedral rhombic crystal, but rather to that of a face in the orthodiagonal zone of a mono- clinic crystal such as (100) or (001). (Fig. 5 shown on (100),) Mineralogy of the H. B. Mine, Salmo, B.C. 9 " It is therefore the opinion of the writer that the mineral may be regarded as monoclinic. If we assume that the best cleavage be (lOo), the second cleavage (010), and the poorest cleavage (ooi), then the twinning-plane and composition- face is (100), and the optic axial plane lies in the orthodiagonal zone and nearly normal to the front pinacoid. In this case the optic angles measured are only approximate, being produced from a series of thin twinned plates parallel to (lOo), each of which, if taken apart from the others would show an angle differing slightly from that obtained on the composite plates. In the same way the value for /3 is not the true value. "The writer has examined carefully the specimens from the mine for crystals of this new mineral, but without success. The stalactitic jnasses, which up to the present are the only form in which it has been observed, are always covered by solution surfaces, a zone between it and the covering silicate having been dissolved away. While from the optical properties the mineral appears to be monoclinic, it would be interesting to confirm this conclusion by direct geometrical measure- ment of crystals. In Fig. 5 the chief crystallographic observations are diagrara- matically represented."' The first description of spencerite having been based on an examination of specimens shewing no crystals the shipment later obtained from the same locality was carefully examined for material suitable for crystallographic measurements. In a few small cavities in the brecciated country rock associated with the stalactitic material some brilliant but small crystals were discovered. They were found to be monoclinic but always twinned with the orthorpinacoid as twinning plane and composition face as had been suggested by the optical examination of the massive material. From the crystallo- graphic description already published^ the following para- graphs are repeated. "Some specimens of this mineral recently obtained from the original locality contain small druses lined with sharp crystals of spencerite, the preservation of the crystals being apparently due to the cavities having been completely sealed up by calamine. "The crystals are very small, few exceeding 2 or 3 mm. in length. They are tabular in habit, and in colour, lustre, and habit closely resemble small, bright crystals of calamine. The crystals, though small, are admirably suited for accurate measurements. The conclusions regarding the crystal form contained in the original contribution are confirmed, since the mineral is found to be mono- clinic, with polysynthetic twinning on the pinacoid (100). 'Walker, T. L., iVIineralogical Magazine, Vol. xviii, 1916. ^Walker, T. L. (Wash. Acad. Sc, Vol. vii. No. 14, 1917). lo Mineralogy of the H. B. Mine, Salmo, B.C. "There are two types of crystals, the first of which is represented in Fig. 6. The peculiarity of this type is the prominence of the pyramid (221) with relatively small terminal faces of the orthodiagonal zone. Crystals of the second type are terminated by what appears to be a large face intersecting the prism edges at 90°. A careful examination shows that this large terminal plane is striated, the faces of the striations belonging to the form (102). (See Fig. 7.) All the crystals measured are twinned and show faces of the two constituent individuals. 345' Fig. 6. — The crystal is twinned on (100) and as_ a result of the twinning the forms (241) and (221) are each represented by four faces, thus giving the crystals a rhombic appearance. HO 100 liOl -X 010 Fig. 7. — Crystals of this type exhibit twinning in the duplication of the terminal faces, (346) being represented by four faces while the two faces of (102) occur as striations on a large plane nearly coinciding in direction with a rhombic basal pinacoid. "The polar elements derived from the measurements are as follows: Po =1-0512; ffo =0.9501; 6 = 0.45071; Ai = 63°i3' corresponding to the axial ratios, a -.b -.c •.: 1. 0125 : i : 1.0643; (3 = 63°i3'. Mineralogy of the H. B. Mine, Salmo, B.C. ii " In Table i are indicated the forms observed and the polar angles 4> and p measured and calculated for the elements indicated above. The number of faces observed for each form on the four crystals measured is shown in the second column."' TABLE I NUMBER rtir »*ir A CI ID IT ^ P FORM. OI" MtAaUKJi- MENTS. Measured. Calculated. Measured. Calculated. I20 12 29° 34' 29° 32' 90° 90° 230 2 35° 50' 37° 04' 90° 90° no II 48° 32' 48° 34' 90° 90° 520 6 71° 07' 70° 34' 90° 90° 010 6 90° 90° 100 6 90° 90° 90° 90° 001 4 89° 56' 90° 26° 52' 26° 47' 104 2 90° 90° II" 20' 11° 30' "102 3 90° 90° 5° 17' 5° 36' 304 I 89° 57' 90° 21° 07' 21° 47' Id 3 89° 53' 90° 34° 55' 35° 02' 201 I 89° 14' 90° 61" 30' 62° 20' 023 I 35° 40' 35° 26' 40° 57' 41" 03' 021 4 13° 30' 13° 21' 65° 32' 65° 25' 121 5 38° 36' 38° 48' 69° 53' 69° 53' 346 3 56° 58' 57^22' 53° 05' 52° 46' in 2 32° 55' 33° 23' 51° 49' 51" 53' 121 6 18° 06' 18° 14' 65° 48' 65° 57' 221 4 41° 52' 41° 52' 70° 41' 70° 43' 241 4 24° 23' 24° 08' 77° 53' 77° 54' Recently in examining crystallized specimens of spencer- ite some small druses were found containing crystals of an unusual habit. They are prismatic with very sharp lance- shaped terminations. Like the crystals previously examined they are very small and bright but they differ from them in being simple individuals. The faces in the prismatic zone 'Walker, T. L., The Crystal Form of Spincerile (Wash. Acad, of Sciences, Vol. vii. p. 456, 1917). 12 Mineralogy of the H. B. Mine, Salmo, B.C. are (lOo), (oio), (no), (120) and (520), while the terminal forms in order of magnitude of the faces are (121), (220), (241) and (102) (Fig. 8). It will be observed that all the terminal faces belong to the upper negative octants so that if the clinographic drawings were made with the usual orien- tation the terminal faces would be scarcely seen. To obviate Fig. 8. this the crystal is shown in Figure 8 turned 180° about the vertical axis. If these simple crystals had been available for the first crystallographic description it is probable that the orientation of spencerite crystals would have been as shown in Figure 8 but as the orientation of the crystals has already Mineralogy of the H. B. Mine, Salmo, B.C. 13 been settled it is not desirable to depart from the first orient- ation. After the formation of the crystals of spencerite they were in most cases covered by a deposit of calamine as it is only in a few small cavities which had apparently been sealed up to prevent this deposition that good crystals are to be observed. In a few of these cavities the spencerite crystals are perfectly bright and free from calamine deposition. In others there are coatings of calamine, sometimes a mere frosting of the crystals while in others the crystals are completely masked. There are many examples of pseudomorphous casts of cala- mine where the thick-walled masses of calamine, rudely resembling the spencerite crystals in shape, are hollow. These casts are very sharp within and appear to have been formed by the deposition of the silicate on crystals of the phosphate followed, in the solution period, by the removal of the substance of the crystals. It is only where these pseudo- morphs of calamine have been broken across that the interior may be observed. As has been already stated the spencerite forms the central part of the stalactitic growths and would appear to have been sealed up by the later shell of calamine. There is frequently observed a solution cavity between the relatively insoluble calamine and the more soluble spencerite. In these ca^•ities are found in small amounts hopeite in fine crystals, complex aggregations of parahopeite and thin-bladed pro- jections of calamine — the adjacent plates parallel to one another suggesting that they had been present as inclusions along the best cleaA-age (100) of spencerite. In the micro- scopic examination of the latter mineral small lenticular inclusions of the same character are often noted. A small quantity of this leafy residual material was the subject of a partial analysis with the followmg result (I) : I II II ZnO 62.87% 67.35% 67.49% SiOz 23.64% 25.32%, 25.01% H2O 6.83% 7.33% 7-50% 93.34 100.00 100.00 14 Mineralogy of the H. B. Mine, Salmo, B.C. Some calcite is present as the material effervesces with dilute hydrochloric acid but this was not quantitatively determined — presumably it constitutes the 6.66 per cent not accounted for in the above analysis. If this analysis be calculated on the basis of I GO the result shown in II is obtained, which agrees very closely with the theoretical composition of calamine (III) HOPEITE This mineral is found in the solution cavities observed on the stalactitic masses of calamine and spencerite. It appears to be a secondary mineral formed from the spencerite. The crystals are never more than three millimeters across and seldom more than one centimeter in length. Hopeite appear to be relatively insoluble as compared with spencerite as the crystals are always sharp and very brilliant. At the H. B. Mine hopeite is a rare mineral, the total amount observed being only a few grammes in weight. Only quali- tative chemical tests were made. The specific gravity as determined by potassic mercuric iodide solution is 3.03. Under the microscope the crystals exhibit parallel extinction in the prismatic zone. The lustre is \4treous except on the macro-pinacoid which is pearly. There are three well marked cleavages corresponding to the three pinacoids. Crystallogilvphic Properties. Five crystals were measured. They resemble one another closely in habit (Fig. 9). The macropinacoid is generally the predominant form. The prism (120) is usually well developed, while of the terminal faces the most prominent are the unit pyramid (in) and the unit macrodome (lOi). The other terminal faces are usually quite small, but, considering their size, remark- able for the accuracy with which they can be measured. The measurements on the larger crystals, while satisfactory, are somewhat less concordant than those obtained from the small crystals. The following forms were observed: Mineralogy of the H. B. Mine, Salmo, B.C. 15 (a) Pyramids (433), (in), (133) and (163) (b) Brachydomes (on) and (021) (c) Macrodomes (103), (loi) and (201) (d) Prisms (670), (120), (s.n.o), (250), (130), (3.n.o) and (160) (e) Pinacoids (010) and (100) The above list contains all the forms observed by Spencer on crystals from Rhodesia except the pyramid (233). The form (201) observed by L^vy in 1837 on material from Aix-la-Chapelle is represented by one face on one crystal. The following forms have not been previously observed : (433) (163) (021) (670) (3-II. (250) Fig. 9. — Hopeite from British Columbia. on two crystals on one of which four faces were ob- served. On this crystal the faces of this new form were the principal terminal faces, observed on only one crystal — faces small but with good reflections. represented by five faces out of a possible six on the three crystals measured, observed on two crystals, o) shown on one crystal, three faces of this form observed on one crystal. i6 Mineralogy of the H. B. Mine, Salmo, B.C. From crystal No. i the polar elements were found to be pa =0.8277, go =0.4720, corresponding to the axial ratios a : b : c : : 0.5703 : i : 0.4720. These ratios are slightly lower than those obtained by previous observers, though they are very near the values of L6vy — a : b : c : : 0.5723 : i : 0.4718. The details of the measurements given in the following table were obtained from crystals i and 2 except the values for the forms (103), (433), (163) and (250). TABLE II. NO. FORM. NO. I OBSERVED. NO. 2 OBSERVED. CALCULATED. Faces 4> P Faces 59° 51' 30° 22' o°35' 0°20' 88° 55' 89° 29' 56° 19' 40° 49' 29° 13' 16° 02' P <^ P I 2 3 4 5 6 7 8 9 10 II 12 13 14 15 16 17 18 Ill 133 433 163 on 021 103 lOI 201 670 J~ ' 5-1 250 130 3.11.0 160 010 100 4 2 8 4 I 2 I 4 I 4 3 I I 2 60° 17' 30° 07' 67° 02' 16° 11' 0° 10' 89° 37' 89° 55' 40° 42' 38° 44' 35° 29° 34' 25° 48' o°o5' 90° 43° 37' 28° 35' 50° 10' 44° 36' 43° 15° 26' 39° 40' 90° ' ■ 90° 90° 90° 90° 90° 89° 42' 4 4 2 2 I I 3 4 4 I 43° 20' 28° 52' 25° 51' 43° 28' 39° 30' 59° 04' 89° 32' 89° 19' 89° 05' 89° 55' 60° 18' 30° 19' 66° 51' 16° 17' 0° 0° 90° 90° 90° 56° 22' 41° 15' 38° 33' 35° 03' 30° 53' 25° 34' 16° 20' 0° 90° 43° 37' 28° 40' 50° 12' 44° 32' 25° 16' 43° 21' 15° 26' 39° 36' 58° 52' 90° 90° 90° 90° 90° 90° 90° 90° 90° All the forms observed on hopeite from the H. B. Mine are shown on the gnomonic projection (Fig. 10). Parahopeite This mineral was first observed by Spencer on specimens from North Western Rhodesia"- where it was associated with hopeite, tarb uttite, calamine, cerussite and other lead and 'Spencer, L. J. (Min. Magazine, Vol. xv, p. i8, 1908). Mineralogy of the H. B. Mine, Salmo, B.C. 17 zinc minerals. The mineral was found by Spencer to be triclinic though the details of its crystallography were not worked out till later.' The discovery of parahopeite along with the other minerals at the H. B. Mine was to be expected owing to the general similarity of the mineral association at the two localities. Fig. 10. — Gnomonic projection of Hopeite from British Columbia. At the H. B. Mine parahopeite is found with hopeite in the solution cavities of the stalactitic masses between the calamine and spencerite. It is far more abundant than the 'Ledoux, Walker and Wheatley (Min. Magazine, Vol. xviii, p. loi, 1917). i8 Mineralogy of the H. B. Mine, Salmo, B.C. hopeite but quite subordinate to the spencerite. The mineral has not been observed in good crystals but rather in fan- shaped aggregates similar to those frequently shown by calamine. These aggregates appear to be built up of crystals in which a partial parallelism of the crystals is preserved, the macropinacoids of the different individuals being more or less common to all the crystals of the aggregate. Occa- sionally small crystals prismatic in habit occur more or less detached, but they are valuable for measurement only, with a view to determining the mineral as parahopeite. The characteristic forms are the prisms (no) and (lio) and the macropinacoid which is usually large but corroded. The principal terminal faces are the pyramid (iTi) and the base (ooi) which is usually represented by a pair of faces due to the characteristic twinning which is polysynthetic with (loo) as twinning plane and composition face. In general the habit of the parahopeite from British Columbia is the same as that from Rhodesia. Physical Properties Parahopeite has a brilliant vitreous lustre. It scratches calcite readily when the striations are made parallel to the shorter diagonal of the cleavage rhombohedron but when attempts are made to scratch calcite parallel to the longer diagonal of the rhomb the striations are very indistinct. Its hardness may therefore be regarded as about 3.5. The specific gravity was determined by means of heavy solutions and by the pycnometer. The former method gave 3.22 while the latter gave 3.236. A determination made by heavy solution on material from Rhodesia showed that the mineral from the type locality has a specific gravity of 3.21. All these values are somewhat lower than those previously published for parahopeite. Like the mineral from Rhodesia the Canadian parahope- ite shows a perfect clea^'age parallel to the brachypinacoid. If crystals be crushed between two glass plates a multitude Mineralogy of the H. B. Mine, Salmo, B.C. 19 of thin cleavage fragments are formed which when examined with the polarising microscope show low double refraction and polysynthetic twinning of the albite type. The extinc- tion angle for individuals is the same as in the case of the mineral from Rhodesia. With convergent polarized light an interference figure showing a single brush may be observed, indicating that an optic axis emerges more or less at right angles to the brachypinacoid. It will be observed that in these many details the Canadian and Rhodesian minerals agree and the enumeration of these physical properties is only with a view to fixing the identity of the minerals. Chemical Properties Some carefully selected small masses of parahopeite were ground up for chemical analysis and dried at 110°. The result of the analysis (I) may be compared with (II) the theoretical composition for parahopeite Zn3(P04)2-4H20. In view of the fact that the selected material was composed of innumerable individuals forming aggregates in which foreign matter would be expected to be present in some proportion, the agreement of the analysis with the theoretical values is remarkably close. I II ZnO 5469 53-270 PjOs 30-46 31 005 H2O 15-31 15-725 100.46 100.000 HiBBENITE In addition to the three zinc phosphates observed by the author on material from the H. B. Mine, Professor A. H. Phillips has described a new zinc phosphate from this mine under the name of hibbenite. It is closely associated with the spencerite in its occurrence and is apparently genetically related to it. The author unfortunately has not observed this new rare mineral on the abundant material at his disposal so that for the sake of completeness it seems desirable to 20 Mineralogy of the H. B. Mine, Salmo, B.C. repeat here some of the principal findings of Professor Phil- lips.' "The combination of forms, the crystal angles and axial ratios are very near that of hopeite as given by J. L. Spencer^. " Chemical Composition — Several crystals were ground, combined in one sample and analyzed with the following results: No. I No. 2 Theoretical ZnO 57-51 57.60 57625 P2O6 28.77 28.88 28.721 HzG 13-74 13-68 13-653 100,02 100.16 99.999 "The above represents the results arrived at from the analysis of the air- dried sample. The sample dissolved readily in dilute acids to a perfectly clear solution leaving no residue and qualitative tests revealed no other elements present, except in traces. The analysis yields the ratios of 7ZnO . 2P2O6 . 7iH20 or 2(Zn8(P04)2) . Zn(0H)2 . 64H2O, a formula which is very satisfactory, with the possible exception of the water. The water is somewhat variable with the condition of the sample. The crystals are filled with small cavities which contain water as shown under the microscope. Water was determined in another sample which had not been exposed to the air as long as the first sample, with the result that it yielded 13.90 per cent. Then a crystal was picked out of the matrix, ground, and the water determined at once with 14.8 per cent, as the result. A portion of this crystal weighing .348 gms. was then tested for loss of water at different temperatures, for comparison with that of spencerite. "It lost at 110° 130° 210° 250° 275° Red Heat 5.74% 7-24% 7-93% 10.05% 11-35% 14-71 The crystals are basic, as is shown both by the high temperature at which a considerable part of the water is given off and by the yellow colour of the hot sample, due to the presence of zinc oxide. "Physical Properties — There are three cleavages parallel to the three pina- coids. Of the three, the brachypinacoidal cleavage is perfect, that parallel to the macropinacoid less so, and the basal cleavage is imperfect. The specific gravity, as determined on small fragments with methylene iodide, varied but little from 3.213. It fuses easily and becomes yellow while hot; decrepitates strongly in the closed tube, yielding much water. Hardness is about 3.75, scratching calcite easily. " Optical Properties — Hibbenite is a pale yellow, almost white, translucent with a vitreous, though somewhat pearly lustre. The double refraction is very weak. Extinction is parallel on all three pinacoidal sections, with the plane of the optic axis parallel to the base. The macroaxis b is the acute bisectrix. Optically negative." 'Phillips, A. H., Loc. cil. ^Mineralogical Magazine, Vol. xv, p. I. Mineralogy of the H. B. Mine, Salmo, B.C. 21 General Relationship of Zinc Phosphates Till recently hopeite was the only natural zinc phosphate known to mineralogists. It had been discovered at Moresnet nearly a century ago and till the discovery of this mineral in Rhodesia by Spencer in 1907 hopeite was known only from the original locality. Along with the hopeite from North- western Rhodesia Spencer discovered two new phosphates of zinc — parahopeite and tarbuttite. The H. B. Mine is the third locality from which phosphates of zinc have been reported. All the previously known phosphates of zinc were found at this new locality except tarbuttite and in addition two new ones — spencerite, which occurs in great abundance, and hibbenite, which is described by Professor Phillips and appears to be very rare. The general chemical relationship of these minerals to one another is as follows: Hopeite — Zn3(P04)2 . 4H2O. — Rhombic Parahopeite — Zn3(P04)2 . 4H2O. — Triclinic Tarbuttite— Zn3(P04)2 . Zn(0H)2— Triclinic Spencerite— Zn3(P04)2 . Zn(0H)2 . 3H2O— Monoclinic Hibbenite— 2Zn3(P04)2 . Zn(0H)2 . 6JH2O— Rhombic From the chemical point of view all these minerals are re- markable for their unusual purity and the general absence of all chemical elements not in accord with the above formulae. The Clay Crust of Stalactitic Masses Outside the calamine shell which surrounds the central core of phosphate is a deposit of clay which is grey to cream in colour. This material which is not plastic was referred to by one of the miners who wrote to Professor Phillips as "very phosphatic clay which carried 20 per cent, zinc and buried in the clay were great chunks of ore". The analysis given below (I) shows that the material examined by me is not particularly phosphatic but that in the zinc content it is comparable to the material mentioned above. 22 Mineralogy of the H. B. Mine, Salmo, B.C. I ZnO 19-99 NiO MgO 3.97 CaO AI2O3 16.07 FezOs 8.01 (FeO) Si02 39-49 P20s 26 H2O II. 12 II III 37-98 32 . 48—36 - 00 .24 .54 .76 13.02 II .70 5-61 29.36 35-64 11-34 14.80—19.88 98-91 98-85 A small amount of carbon dioxide is present in the clay but this was not determined. Clays carrying considerable amounts of zinc have been frequently observed in connection with oxidized zinc ores. The analysis of such a clay from Moresnet is shown in (II) while (HI) is an incomplete analysis of a zinciferous clay from Sterling Hill, N.J. These two clays have been described as distinct minerals under the names Moresnetite and Vanuxemite. They are doubtless of the same general nature as the clay from the H. B. Mine and are probably mixtures of some zinc mineral with clay. The Origin of the Phosphates In the case of the deposits of zinc phosphates in Rhodesia the minerals are sometimes associated with organic remains in caves containing implements indicating that they had been occupied by men at an early period. The phosphates are sometimes deposited on bones or on bone breccias. At other times they were formed quite remote from animal phosphate deposits. The Canadian zinc phosphates as has been men- tioned occur in crystalline limestone, which is supposed to be carboniferous in age. The cave in the H. B. Mine had one dyke as a wall and another as roof. It was found that while the mine as a whole was unusually dry, there was an abund- ance of water entering the cave. The phosphoric acid neces- sary for the formation of the phosphates may have been derived from solution of apatite in the dykes or the source of the phosphoric acid may be in the carboniferous rocks. Mineralogy of the H. B. Mine, Salmo, B.C. 23 It may be of interest in this connection to note that quite recently De Schmid^ has found, in the eastern Rocky Moun- tains, beds of phosphates in the upper 50 feet of the Rocky Mountain quartzite which is also carboniferous. No such beds have been found in the vicinity of the H. B. Mine but it is not improbable that the phosphoric acid entering into the zinc phosphates here described may be derived from some bed of phosphate more or less equivalent to those discovered by De Schmid farther east. In the carboniferous a few miles north of the H. B. Mine, Drysdale^ reports the occurrence of pyromorphite at the Old Timer Mine. Cerussite Cerussite has not been observed in association with the phosphates found in the cave but throughout the ore body along with calamine and limonite it is generally distributed. An account of some exceedingly beautiful specimens of cerussite from this mine was recently published.' The crystals are water clear with very brilliant faces and well suited for exact goniometric measurements. This is probably the finest crystallized cerussite found in Canada. The crystals are almost invariably twinned forming six- rayed structures such as have been frequently observed for this mineral. In these complex growths the twinning ordin- arily observed occurs on the face of the prism (no) but in the case of the Salmo mineral the structures are often more com- plex in that several of the individuals are twinned on (no) while one of these is twinned on another individual with (130) as the twinning plane. In many minerals complex twins involving more than one twinning law are common but the stellate interpenetration twins of cerussite have been regarded till recently as resulting from twinning according to one law only. iDe Schmid, H. S. (Mines Branch, Bull. No. 12, Ottawa, 1916). ^Drysdale, C. W., Ymir Mining Camp (Geol. Surv. Can. Ottawa, p. 570, 1917). ^Ledoux, A., and Walker, T. L., Cerussite from Salmo, B.C. (Ottawa Nat. 1918). 24 Mineralogy of the H. B. Mine, Salmo, B.C. On crystals measured the following forms have been observed : (a) Pinacoids Basal pinacoid (ooi) usually rough and when pre- sent large. Brachy pinacoid (oio) always the largest face so that the crystals are tabular. Macropinacoid (lOo) narrow and well defined. (b) Prisms — (no) and (130). (c) Brachydomes — ^(012), (on), (021), (052), (031), (041), (092), (051), (061), (071), (081), (091), (o.io.i), and (0.12. i). (d) Macrodome — (102). (e) Pyramids — (in) and rarely (112). The domes (012) and (021) are the most prominent. The others are present in certain crystals and give with the goniometer a long series of reflections. The brachydomes (092) and (0.12.1) were first observed on cerussite from this locality. Mineralogy of the H. B. Mine, Salmo, B.C. 25 Bibliography on H. B. Mine Galloway, J. D., Report of the Minister of Mines of British Columbia, 1905, p. 160. Ledoux, A., and Walker, T. L., Cerussite from Salmo, B.C. Ottawa Naturalist, 1918. Phillips, A. H., New Zinc Phosphates from Salmo, British Columbia, American Journal of Science, Vol. XLII, p. 275, 1916. Walker, T. L., Spencerite, a New Zinc Phosphate from British Columbia, Mineralogical Magazine, Vol. XVIII, p. 76, 1916. (Abstracts in Nature, June 29th, 1916, and Geological Magazine July 1916). Walker, T. L., Hopeite from the H. B. Mine, Salmo, B.C., Journal Washington Academy of Sciences, Vol. VI, p. 685, 1916. Walker, T. L., The Crystal Form of Spencerite, Journal Washington Academy of Sciences, Vol. VII, p. 456, 1917. UNIVERSITY OF TORONTO STUDIES Geological Series. No. I : The Huronian of the Moose River basin, by Pro- fessor W. A. Parks $i .00 No. 2 The Michipicoten iron rang-es, by Professor A. P. Coleman and W. A. Willmott i.oo No. 3 : The geology of Michipicoten Island, by E. M. BURW.VHH I.OO No. 4 . The stromatoporoids of the Guelph formation in Ontario, by Professor W. A. Parks 1. 00 No. 5 Niagara stromatoporoids, by Professor W. A. Parks i.oo No. 6 : Silurian stromatoporoids of America, by Professor W. A. Parks 1 .00 No. 7 Ordovician stromatoporoids, by Professor W. A. Parks I.OO No. S : A Cervalces antler from the Toronto Interglacial, by Professor B. A. Bexsley I.OO No. 9; Palaeozoic fossils from a region southwest of Hudson Bay, by Professor W. A. Parks I.OO No. 10: Mineralogy of the H. B. Mine, Salmo, B.C., by Professor T. L. Walker O.50 Ljaulora PAM PHLET BINDER I^^T Syracuse, N. Y. ■ Stockton, Calif.