5 to*/ .9- STATE OF ILLINOIS DWIGHT H. GREEN, Governor DEPARTMENT OF REGISTRATION AND EDUCATION FRANK G. THOMPSON, Director DIVISION OF THE STATE GEOLOGICAL SURVEY M. M. LEIGHTON, Chief URBANA REPORT OF INVESTIGATIONS— NO. 104 ILLINOIS SURFACE CLAYS AS BONDING CLAYS FOR MOLDING SANDS An Exploratory Study R. M. Grogan and J. E. Lamar PRINTED BY AUTHORITY OF THE STATE OF ILLINOIS URBANA, ILLINOIS 1945 ILLINOIS STATE GEOLOGICAL SURVEY 3 3051 00005 7459 STATE OF ILLINOIS DWIGHT H. GREEN, Governor DEPARTMENT OF REGISTRATION AND EDUCATION FRANK G. THOMPSON, Director DIVISION OF THE STATE GEOLOGICAL SURVEY M. M. LEIGHTON, Chief URBANA REPORT OF INVESTIGATIONS— NO. 104 ILLINOIS SURFACE CLAYS AS BONDING CLAYS FOR MOLDING SANDS An Exploratory Study R. M. Grogan and J. E. Lamar PRINTED BY AUTHORITY OF THE STATE OF ILLINOIS URBANA, ILLINOIS 1945 ORGANIZATION STATE OF ILLINOIS HON. DWIGHT H. GREEN, Governor DEPARTMENT OF REGISTRATION AND EDUCATION HON. FRANK G. THOMPSON, Director BOARD OF NATURAL RESOURCES AND CONSERVATION HON. FRANK G. THOMPSON, Chairman NORMAN L. BOWEN, Ph.D., D.Sc, LL.D., Geology ROGER ADAMS, Ph.D., D.Sc, Chemistry LOUIS R. HOWSON, C.E., Engineering ♦WILLIAM TRELEASE, D.Sc, LL.D., Biology EZRA JACOB KRAUS, Ph.D., D.Sc, Forestry ARTHUR CUTTS WILLARD, D.Engr., LL.D. President of the University of Illinois GEOLOGICAL SURVEY DIVISION M. M. LEIGHTON, Chief ♦Deceased. (81613— 2M— 4-45) SCIENTIFIC AND TECHNICAL STAFF OF THE STATE GEOLOGICAL SURVEY DIVISION 100 Natural Resources Building, Urbana M. M. LEIGHTOX, Ph.D., Chief Enid Townley, M.S., Assistant to the Chief Velda A. Millard, Junior Asst. to the Chief Helen E. McMorris, Secretary to the Chief Effie Hetishee, B.S., Geological Assistant GEOLOGICAL RESOURCES Coal G. H. Cady, Ph.D., Senior Geologist and Head L. C. McCabe, Ph.D., Geologist (on leave) R. J. Helfinstine, M.S., Mech. Engineer Charles C. Boley, M.S., Assoc. Mining Eng. Heinz A. Lowenstam, Ph.D., Assoc. Geologist Bryan Parks, M.S., Asst. Geologist Earle F. Taylor, M.S., Asst. Geologist (on leave) Ralph F. Strete, A.M., Asst. Geologist M W. Pullen, Jr., M.S., Asst. Geologist Robert M. Kosanke, M.A., Asst. Geologist Robert W. Ellingwood, B.S., Asst. Geologist George M. Wilson, M.S., Asst. Geologist Arnold Eddings, B.A., Research Assistant (on leave) Henry L. Smith, A.B., Asst. Geologist Raymond Siever, B.S., Research Assistant (on leave) John A. Harrison, B.S., Research Assistant (on leave) Mary E. Barnes, B.S., Research Assistant Margaret Parker, B.S., Research Assistant Elizabeth Lohmann, B.F.A., Technical Assistant Industrial Minerals J. E. Lamar, B.S., Geologist and Head H. B. Willman, Ph.D., Geologist Robert M. Grogan, Ph.D., Assoc. Geologist Robert T. Anderson, M.A., Asst. Physicist Robert R. Reynolds, M.S., Asst. Geologist Margaret C. Godwin, A.B., Asst. Geologist Oil and Gas A. H. Bell, Ph.D., Geologist and Head Carl A. Bays, Ph.D., Geologist and Engineer Frederick Squires, B.S., Petroleum Engineer Stewart Folk, M.S., Assoc. Geologist (on leave) Ernest P. DuBois, Ph.D., Assoc. Geologist David H. Swann, Ph.D., Assoc. Geologist Virginia Kline, Ph.D., Assoc. Geologist Paul G. Luckhardt, M.S., Asst. Geologist (on leave) Wayne F. Meents, Asst. Geologist James S. Yolton, M.S., Asst. Geologist Robert X. M. Urash, B.S., Research Assistant Margaret Sands, B.S., Research Assistant Areal and Engineering Geology Ph.D., Geologist and Head M.S., Asst. Geologist George E. Ekblaw, Richard F. Fisher, Subsurface Geology L. E. Workman, M.S., Geologist and Head Carl A. Bays, Ph.D., Geologist and Engineer Robert R. Storm, A.B., Assoc. Geologist Arnold C. Mason, B.S., Assoc. Geologist (on leave) C. Leland Horberg, Ph.D., Assoc. Geologist Frank E. Tippie, B.S., Asst. Geologist Merlyn B. Buhle, M.S., Asst. Geologist Paul Herbert, Jr., B.S., Asst. Geologist Charles G. Johnson, A.B., Asst. Geologist (on leave) Margaret Castle, Asst. Geologic Draftsman Marvin P. Meyer, B.S., Asst. Geologist Robert X. M. Urash, B.S., Research Assistant Elizabeth Pretzer, A.B., Research Assistant Ruth E. Roth, B.S., Research Assistant Stratigraphy and Paleontology J. Marvin Weller, Ph.D., Geologist and Head Chalmer L. Cooper, M.S., Assoc. Geologist Petrography Ralph E. Grim, Ph.D., Petrographer Richards A. Rowland, Ph.D., Asst. Petrographer (on leave) William A. White, B.S., Research Assistant Physics R. J. Piersol, Ph.D., Physicist B. J. Greenwood, B.S., Mech. Engineer GEOCHEMISTRY Frank H. Reed, Ph.D., Chief Chemist H. W. Jackman, M.S.E., Chemical Engineer P. W. Henline, M.S., Assoc. Chemical Engineer James C. McCullough, Research Associate James H. Hanes, B.S., Research Assistant (on leave) Leroy S. Miller, B.S., Research Assistant Elizabeth Ross Mills, M.S., Research Assistant Coal G. R. Yohe, Ph.D., Chemist Herman S. Levine, B.S., Research Assistant Industrial Minerals J. S. Machin, Ph.D., Chemist and Head Delbert L. Hanna, A.M., Asst. Chemist Fluorspar G. C. Finger, Ph.D., Chemist Oren F. Williams, B.Engr., Research Assistant X-ray and Spectrograph}' W. F. Bradley, Ph.D., Chemist Analytical O. W. Rees, Ph.D., Chemist and Head L. D. McYicker, B.S., Chemist Howard S. Clark, A.B., Assoc. Chemist William F. Wagner, M.S., Asst. Chemist Cameron D. Lewis, B.A., Asst. Chemist Herbert X. Hazelkorn, B.S., Research Assistant William T. Abel, B.A., Research Assistant Melvin A. Rebenstorf, B.S., Research Assistant Marian C. Stoffel, B.S., Research Assistant Jean Lois Rosselot, A.B., Research Assistant MINERAL ECONOMICS W. H. Yoskuil, Ph.D., Mineral Economist Douglas F. Stevens, M.E., Research Associate Ethel M. King, Research Assistant PUBLICATIONS AND RECORDS George E. Ekblaw, Ph.D., Geologic Editor Chalmer L. Cooper, M.S., Geologic Editor Dorothy E. Rose, B.S., Technical Editor Meredith M. Calkins, Geologic Draftsman Beulah Featherstone, B.F.A., Asst. Geologic Draftsman Willis L. Busch, Principal Technical Assistant Portia Allyn Smith, Technical Files Clerk Alicia Woodall, Technical Assistant Leslie D. Vaughan, Asst. Photographer Consultants: Ceramics, Cullen W. Parmelee, M.S., D.Sc, and Ralph K. Hcrsh, B.S., University of Illinois Mechanical Engineering, Seichi Konzo, M.S., University of Illinois Topographic Mapping in Cooperation with the United States Geological Survey. This report is a Contribution of the Industrial Minerals Division, April 10. 1945 Digitized by the Internet Archive in 2012 with funding from University of Illinois Urbana-Champaign http://archive.org/details/illinoissurfacec104grog CONTENTS Page Abstract 7 Introduction 8 Basis for selection of samples 9 Distribution and character of surface clay deposits sampled 9 Till 9 Gumbotils and associated clays 9 Loess 11 Lake clays 11 Residual clays 11 Other clays 12 Chemical analyses 12 Preparation of samples for testing 12 Pulverized natural and de-pebbled clays 13 Clay concentrates 13 Air-separated fractions 13 Testing sand 17 Testing procedure 17 Results of tests 18 Interpretation of test data 18 Natural and de-pebbled clays 18 Green compressive strength 18 Dry compressive strength 18 Compressive strength and content of minus 0.002 mm. material 18 Mineral composition 19 Clay concentrates 19 Green compressive strength 20 Dry compressive strength 19 Effect of eliminating material larger than 0.002 mm 19 Air-separated fractions i 19 Green compressive strength 19 Dry compressive strength 20 Permeability 20 General effect of different size fractions 20 Particle size composition of clays and strength of minus 0.010 mm. air-separated fractions 21 Influence of clay mineral composition 21 Illinois surface clays and beneficiation 36 Appendix — Description of deposits sampled 37 ILLUSTRATIONS Figure Page 1 Location and type of sampled deposits of Illinois surface clays 10 2 A Curves showing green and dry compressive strengths (at various moisture contents) of synthetic sands containing commercial bond clays and bentonites, and surface clays 28 2B Curves showing green and dry compressive strengths (at various moisture contents) of synthetic sands containing air-separated fractions and clay concentrates 30 TABLES 1 Chemical analyses of surface clays 12 2 Location and thickness of deposits sampled and mechanical analyses of field samples of surface clays 14 3 Sieve analyses of disc-pulverized natural and de-pebbled clays 16 4 Results of air-classification of ground surface clays 16 5 Particle size distribution of selected gumbotils and associated clays and of air- separated fractions from the same samples 17 6 Average sieve test of testing sand 17 7 Results of bonding tests 22 8 Strength data at comparable moisture contents 32 9 Index to samples 34 10 Green compressive strengths of several clays and of the corresponding clay concentrates 34 11 Green and dry compressive strengths imparted by sample 18 and by various size fractions derived from it 35 ILLINOIS SURFACE CLAYS AS BONDING CLAYS FOR MOLDING SANDS An Exploratory Study BY R. M. Grogak and J. E. Lamar Abstract SAMPLES of surface clays from various parts of Illinois, including one sample of glacial till, twelve gumbotils and associated clays, one loess, three lake clays, seven residual clays, and three miscellaneous clays, were tested for green and dry compressive strength in parallel with several commercial bonding clays, including fireclays and bentonites, to determine their value as bonding clays for synthetic molding sands. The compressive strength tests were made according to procedures approved by the American Foundrymen's Association. They involve determining the strength of a moist mixture of silica sand and the clay being tested or of a similar mixture which has been allowed to dry. The amounts of sand, clay, and moisture present are care- fully proportioned. The results of the tests on sand-clay mixtures containing the natural clays, un- modified except for the removal of pebbles from pebbly samples, indicate that with 8 percent clay and 2 percent moisture, six of the samples possessed green compressive strengths equal to or greater than those of three of the nonbentonitic commercial bond- ing clays. The dry compressive strengths of most of the surface clays equalled or ex- ceeded those of the nonbentonitic commer- cial bonding clays. The bonding ability of some clays was considerably improved by removing all the material larger than 0.002 mm. by water- classification. Tests on sand-clay mixtures containing 2 percent moisture and 8 percent of the pulverized water-separated clay con- centrate from three surface clays, in- cluding two lake clays and one gumbotil. showed an increase in green compressive strength of 2 to 9]/> times that of the un- modified clay. The green compressive strengths imparted by two of the clay con- centrates compared favorably with green strengths given by the bentonites, 4 percent clay and 2 percent moisture being used for all tests. The dry strengths were somewhat lower than those of the bentonites. An increase in bonding ability also resulted from the removal of coarse material from a sample of gumbotil by air-separation. Before air-classification the green compres- sive strength of this clay was less than that of any of the commercial bonding clays used for comparison. However, the air- separated minus 0.010 mm. fraction gave a green strength greater than any of the four nonbentonitic commercial clays using 8 per- cent clay and 2 percent moisture for all tests. Air-separated fractions of a number of additional gumbotils and associated clays were also prepared. Most of the minus 0.010 mm. fractions, in sand-clay mixtures employing 8 percent of clay and 2 percent moisture, exceeded in green compressive strength the two bentonites tested at 4 per- cent clay, 2 percent moisture. The dry compressive strengths imparted by 8 per- cent of these fractions approximated those given by the bentonites at 4 percent clay. [7] 8 SURFACE CLAYS AS BONDING CLAYS The minus 0.050 mm. and the plus 0.050 mm. air-separated fractions generally gave lower green compressive strengths than the minus 0.010 mm. fraction at the same moisture content when 8 percent clay was used in sand-clay mixtures. The dry com- pressive strengths of both fractions were generally similar to those produced by the bentonites at 4 percent clay. The green and dry compressive strengths of the samples tested are related to the relative amounts of clay-size (minus 0.002 mm.) and silt-size (0.002 mm. to 0.053 mm.) material present in the samples. In general it was found that the more clay- size material in a surface clay the higher its green compressive strength, and the more silt-size material in a clay the higher its dry compressive strength. These relations may prove useful in prospecting for bonding clay even if beneflciation by removal of sand is planned, for they appear to be true of the air-separated fractions as well as of the unmodified clays. From the tests it appears that the Cre- taceous clays tested, some residual clays, and possibly some lake clays would be suit- able in their natural state, or after coarse screening, for ordinary foundry use. The other clays would need more or less bene- flciation in order to compare favorably with commercial bonding clays. Some surface clays may be made to have bond strengths comparable to those of the bentonites by either hydraulic or air-classification. Introduction "Surface clays" are defined for this report as those clays occurring at or near the surface of the ground, including clays resulting from the weathering of bedrock. Extensive deposits of surface clays exist at many places in Illinois, but in general they are not much used commercially except locally for the manufacture of structural clay products. Because significant data are lacking regarding the suitability of these clays for purposes other than for making clay products, a study was undertaken to secure such data. A previous report * gave preliminary information about gumbotil, one kind of surface clay, as drilling mud, bonding clay, and bleaching clay. The present report extends the study of bonding properties to include further data regarding gumbotil as well as similar information about a number of other surface clays. In contrast to "natural bonded" molding sands which as found in nature contain enough clay to bond them, that is, to cause the sand grains to adhere to one another, "synthetic" molding sands are prepared by adding a bonding clay to a clean sand of suitable grain size. Although natural bond- ed molding sands are extensively employed, synthetic sands 2 are also widely used and their use is increasing. In the Middle West the bonding clays commonly used for synthetic sands are fireclay and bentonite. Although in the Middle West there is probably no scarcity of fireclay and other clays which can be used as bonding clay, few materials having properties which approach or equal those of bentonite are known. For this reason the work covered by this report had as its aim the discovery of Illinois surface clays whose bonding properties are better than those of fireclay and as nearly like those of bentonite as possible. Twenty-seven typical Illinois surface clays, all of them noncalcareous, were selected for study together with six commer- cial bonding clays including four produced in the Middle West, a Southern bentonite from northern Mississippi, and a Western bentonite from the Black Hills area. The results of the tests on the commercial clays serve as standards for evaluating the possi- bilities of the Illinois materials. 1 Lamar, j. E., Grim, R. E., and Grogan, R. M., Gum- botil as a potential source of rotary drilling mud, bonding clay and bleaching clay: Illinois Geol. Survey, Cir. 39, July IS, 1938. 2 The term "synthetic sands" is used hereafter to denote both commercially prepared synthetic molding sands and, more commonly, the laboratory mixtures of sand and pulverized clay used in the bond clay tests. DEPOSITS SAMPLED Basis for Selection of Samples The surface clays of Illinois may be classified into six general categories as follows : ( 1 ) till deposited by continental glaciers; (2) gumbotil produced by pro- longed weathering of till under special con- ditions; (3) loess formed by the deposition of fine-sized wind-borne material; (4) lake clay deposited in old lake basins; (5) re- sidual clay mostly resulting from the weathering of limestones; and (6) certain other clays, three of which are included in this investigation. The clay samples selected for the present study comprise only a small fraction of the total number taken for the general study of Illinois surface clays. They were chosen to represent the various types of surface clays, both with respect to kind of deposit and to mineral composition. All are from deposits free from calcareous materials or are from the noncalcareous weathered por- tions of deposits which were originally cal- careous throughout. The general location of the sampled deposits is shown in figure 1. Bonding clays are composed of one or more of the clay minerals illite, kaolinite, or montmorillonite, plus various amounts of nonclay minerals such as quartz, limo- nite, and mica. Bentonites, for example, are made up dominantly of the clay mineral montmorillonite, whereas fireclays are commonly mixtures of kaolinite, illite, and quartz. Preliminary microscopic and X-ray examination indicated that a number of the surface clays contain montmorillonite. These clays were given particular attention because of the possibility that the presence of the montmorillonite might give them properties approaching those of bentonite. In general it was necessary to take samples where favorable conditions existed, as in cuts along streams, railroads, or roads. All the samples are believed to have come from deposits of considerable size although not necessarily from the place most suit- able for commercial development. They represent, therefore, the types of surface clays and surficial clay deposits occurring in Illinois, but there exist many other deposits than those tested, and any attempt at development should be preceded by a study of the relation of available deposits to market areas, followed by careful prospect- ing and testing of the deposits to determine their extent and character. Distribution and Character of Surface Clay Deposits Sampled till Till is a sandy pebbly clay deposited by glaciers. Unweathered till commonly con- tains many limestone pebbles and other calcareous material and is therefore unsuit- ed for use as bonding clay. During weather- ing, however, water percolating through the deposit dissolves and removes the cal- careous material, leaving behind a noncal- careous gray or brown plastic clay better suited to foundry use. Pebbles other than those composed of limestone are also left behind to form a part of the weathered deposit. These pebbles vary in abundance from place to place. Till is widespread in Illinois, occurring over the entire State except in extreme southern Illinois, parts of Calhoun and Carroll counties, and the northwest corner of the State. In most of northeastern Illinois the thickness of the nocalcareous till rarely exceeds 2 feet, but elsewhere the thickness may be twice that great. Sample 48, described in the appendix, is leached till. GUMBOTILS AND ASSOCIATED CLAYS Gumbotil is a product of the extreme weathering of glacial till on flat uplands under conditions of poor drainage. It is a highly plastic, gray or brown clay, common- ly pebbly but less pebbly than the parent till, containing silt and sand in amounts which vary widely in different localities. When dried, the clayey and silty varieties become hard and tough, whereas the sandy varieties are usually crumbly and friable. Deposits occur in central, southern, and western Illinois. Because overburden on the gumbotil is relatively thin in south-central Illinois, the deposits in that area were 10 SURFACE CLAYS AS BONDING CLAYS TYPE OF DEPOSIT • Residual clay Q T. 3 GumboHl ■ Loess G2 Lake clay A Other clays J040M.LES Fig. 1. — Location and type of sampled deposits of Illinois surface clays. DEPOSITS SAMPLED 11 given more attention than those elsewhere. Samples from nine of these deposits were tested during the present study. Further details of the general occurrence, extent, and character of Illinois gumbotil deposits are given in Circular 39. 3 Immediately below the gumbotil there is normally a zone of noncalcareous clay 4 whose character is intermediate between that of the gumbotil above and the cal- careous relatively unaltered till below. As it lies immediately below gumbotil and might considerably increase the workable thickness of clay in a given area if proved suitable for bonding use, samples of this clay were taken for testing from three localities that were also sampled for gum- botil. They bear the same sample number as the gumbotils but are distinguished from them by the suffix A added to the sample number. Descriptions of deposits sampled are given in the appendix and include samples 18, 55, 55A, 56, 57, 58, 58A, 59, 59A, 60, 61, and 62. LOESS Loess is a wind-deposited brown clayey silt occurring over large areas on the up- lands adjacent to Mississippi, Illinois, and Ohio rivers. It is the surficial material throughout much of western and southern Illinois. The unweathered loess is common- ly calcareous except in extreme southern Illinois, but the upper part of many deposits has been leached by weathering to a depth of 2 to 4 feet. Only noncalcareous loess was investigated, as calcareous material is con- sidered deleterious in bonding clay. Sample 49, described in the appendix, is loess. LAKE CLAYS The lake clays studied were deposited in lakes associated with glaciers which once 3 Lamar, J. E., Grim, R. E., and Grogan, R. M. Gum- botil as a potential source of rotary drilling mud, bonding clay, and bleaching clay; Illinois Geol. Survey Cir. 39, July 15, 1938. 4 Zone 3 of the "soil profile." For a detailed description of its character and origin see Leighton, M. M.. and MacClintock, Paul, Weathered zones of the drift sheets of Illinois: Illinois Geol. Survey, Report of In- vestigations No. 20, 1930. covered most of Illinois. These clays gener- ally contain a considerable proportion of silt. Although the clays were calcareous when deposited, leaching has removed the cal- careous material from the upper part of the deposits to a depth of 2 to 5 feet. Only the leached part of the deposits was studied. Samples 3, 53 and 150, described in the appendix, are lake clays. RESIDUAL CLAYS Most of the residual clays found in Illinois have been formed by the weathering of limestone and are the insoluble materials left behind when w r ater leached away the soluble portions of the limestone. Obviously the character of these clays is directly related to the character of the original limestones, cherty limestones giving rise to cherty clays, for example, and sandy lime- stones to sandy clays. The residual clays are commonly red or brow 7 n owing to their content of hydrated iron oxides, though in a few places white or cream-colored clays have developed from limestones. Many residual clays contain angular chert fragments, although some are free from chert. Because the dowmward progress of leach- ing is rarely uniform, it is probable that the limestone floor of most deposits is uneven, and that as a consequence the thickness of the clay in any deposit is likely to be vari- able. It is thought likely that residual clays are generally thickest a short distance below the tops of hills, ridges, or upland flats underlain by limestone where slumping of the clays has made their thickness greater than normal. No deposits were observed whose thickness is consistently greater than 15 feet, but exposures of clay 5 to 10 feet thick are relatively common. The overburden on the residual clays is generally a few feet to as much as 25 feet of brown clayey silt. Considerable tonnages of clay can probably be obtained with less than 10 feet of overburden. Residual clays occur in three principal areas in the State (fig. 1): (1) Union, Johnson, Pope, Massac, and Hardin coun- ties in extreme southern Illinois; (2) Cal- 12 SURFACE CLAYS AS BONDING CLAYS houn, Pike, and possibly some adjacent counties in western Illinois; and (3) the extreme northwest corner of the State. Samples of typical residual clay from seven deposits were chosen for study and are described in the appendix, including samples 8, 21, 24, 31, 44, 50, and 52. OTHER CLAYS Three samples have been placed in this category. Sample 4 is from a deposit of Cretaceous age, sample 54 is probably of Creaceous age, and sample 45 is from a glacial deposit. Chemical Analyses Chemical analyses are not generally reli- able guides to the bonding characteristics of clays except in a broad way. For this reason only a few analyses were made of Illinois surface clays, chiefly to supplement the information on the mineralogic and mechan- ical composition of some of the more prom- ising materials studied. Analyses of four clays are given in table 1. Silica, alumina, and combined water (loss on ignition) are the principal con- stituents of the clays. They reflect the presence of clay minerals, which are essen- tially hydrous aluminum silicates, and in some samples, the presence of free silica in the form of sand and silt. Sample 18 shows more silica than the other samples because it contains more sand and silt (table 1). The total soda and potassia in each sample is in a large degree an indication of the relative amounts of soda- and potash-bearing clay minerals, such as illite and montmorillonite, in that clay. The chief clay mineral present in the kaolin is kaolinite, which contains very little soda and potassia. Preparation of Samples for Testing The commercial bonding clays (excepting the bentonites) were received in lump form and were ground in a disc pulverizer in preparation for bond tests. The bentonites were received already ground. The samples of surface clays were pre- pared for testing by one of three methods : ( 1 ) grinding all of that part of the sample which passed a 4-mesh sieve; (2) concen- trating and removing from the original sample by water-separation that fraction composed of particles less than 0.002 mm. in diameter, followed by drying and grind- ing; and (3) air-separating three size frac- tions from pulverized clay from which the plus 4-mesh material had been removed before grinding. Table 1. — Chemical Analyses of Surface Clays' Sample b 4 Sample 18 Sample 21 Kaolin d Si0 2 . 59.60 0.72 26.48 2.39 0".77 0.44 0.37 1.67 8.03 79.04 0.51 11.04 3.47 0.03 0.72 0.39 0.85 1.45 3.18 56.96 0.37 23.47 8.84 6 '.82 0.53 0.30 1.56 7.92 51.10 Ti0 2 . 0.95 A1 2 3 34.01 Fe 2 3 1.41 MnO MgO . . 0.37 CaO 0.15 Na 2 0.36 K 2 . 0.31 Loss on ignition 11.95 Total 100.47 100.65 100.77 100.61 a Analyses made under the direction of O. W. Rees, State Geological Survey. b Sample 4, Cretaceous clay; 18, gumbotil ; 21, residual clay; Kaolin, Cretaceous clay. c Average of two analyses. d Analysis of crucible clay from deposit near Kaolin Station, Union County, similar to sample 54. PREPARATION FOR TESTING 13 PULVERIZED NATURAL AND DE-PEBBLED CLAYS The first method involved air-drying, breaking of lumps, and thorough mixing of the field sample, after which a small rep- resentative portion was separated by a Jones-type sample splitter and set aside for mechanical analysis. If the sample contained pebbles these were removed by hand-pick- ing. The plus 4-mesh material thus segre- gated was weighed and discarded. About 15 pounds of the pebble-free material, or of the original sample if it contained no pebbles, was then ground in a disc pulver- izer, and the resulting product was used in bonding tests. In discussing results of these tests samples prepared as indicated above are referred to as "natural" if they con- tained no pebbles and as "de-pebbled" if pebbles were removed. Mechanical analyses of the original field samples are given in table 2. Sieve analyses of the pulverized samples are given in table 3. CLAY CONXEXTRATES The upper size limit of the material that is believed to consist largely of clay minerals in the samples studied is about 0.002 mm. The amount of this material is less than 40 percent in many of the samples. To deter- mine the properties of this clay mineral material, especially in samples appearing to contain montmorillonite, the minus 0.002 mm. fractions of samples 3, 18, and 150 were separated by suspending the sample in water to which a small amount of sodium oxalate had been added to insure dispersion of the clay mineral material, and after an appropriate settling period the minus 0.002 mm. material in suspension was siphoned off. The clay mineral concentrates thus ob- tained were dried and pulverized in prepa- ration for use in bonding tests. AIR-SEPARATED FRACTIONS By means of a laboratory air classifier, selected samples that had been previously pulverized after removing any pebbles present, were sized to three fractions: minus 0.010 mm., 0.010 to 0.050 mm., and plus 0.050 mm., which is roughly plus 270- mesh. Microscopic examination showed a small amount of particle size overlap be- tween fractions. Average yields of the three air-separated tractions for each sample are given in table 4. The results of hydrometer analyses of unground clay and the air-separated frac- tions for samples 18, 59, and 59A are given in table 5. A comparison of the data in table 4 and the results of hydrometer analyses of the unground samples and minus 0.010 mm. fractions, table 5, indicates that only 26 and 27 percent, respectively, of the minus 0.010 mm. material in samples 18 and 59, and 63 percent of that in sample 59A was ac- tually recovered by air-separation. This is thought to be due partly to imperfect separation of particles of various sizes in the air classifier, but more largely to in- complete disintegration of samples during grinding. Minus 0.010 mm. material is present in the plus 0.010 mm. fractions, both as particles below 0.010 mm. in size which were not removed by air-separation, and as particles bound up in aggregates not completely disintegrated into minus 0.010 mm. particles during grinding. Commercial processes are probably available which would achieve better disintegration of samples and thus permit greater recovery of minus 0.010 mm. material than was possible with the laboratory equipment em- ployed in this work. Calculations based on the data in tables 4 and 5 indicate that a minor amount of plus 0.010 mm. material was reduced to minus 0.010 mm. size as a result of the grinding procedure used. Bonding tests were made on the three air- separated fractions: minus 0.010 mm.; minus 0.050 mm. (obtained by recombining parts of the minus 0.010 mm. and 0.010 mm. to 0.050 mm. fractions in their proper proportions) ; and plus 0.050 mm. 14 SURFACE CLAYS AS BONDING CLAYS co V 03 © oo "f r- 1 + - £ r- o n b £ as T _c r CO T3 u F C H n o co ^ CN i + ~ £ r- O E 03 CN as T U tfi r oi^ CO CN 0} « u •o a LO 03 (J r> <0 CO 05 09 T3 G 03 o «3 4-1 CO X! a 3 o ^c i — ■^••n^ocor^r-©^ ^O^^OOOcotSO^O CN' \0 - \r^so i nr^' N r0OtNr0tri(NM(N(N\0'*^ ^^nooo^^vootso^o rHioOKKNrHOrorivD-O n(N(N(N(NrO(NrotNrinro \JN \M \N\W\*)l\CO\W COCOCN^O-^CNcOCNcorNCNCN r C _ c/ tow Hil ck. idv >_c C O c - 5 - 3 £ 3 Louis Mars Mont Toled Brow Wain Swan Kinm TJ C 03 "5- £ ' § c Clay. Clark Cumb Fayet Jeffers Perry Mario < < < OOiO^^Oh-OOOOONONO'-^M HI tn U") lO v> >~r, LO in ^o vO «C PQ oo o r- W) CO Tf oo o o o o oo o r- v> (N CN if) Ih 3 03 co u. P "C ^ 03 03 rs 0-o <-o o O O r^ rt< co i— i O oo vO <-o oo \o O O O ^o o vO vO •* O CM On oo cn t^ oo n ^ so \o £ £ £~ 2 £ i, _C c 3 U -C ^ ^ rt ° - JS W ^ U c£ w 51 ;3 o « : *-; rt « n rt OJ Tf t^ gco^ 4-J -Jf o oo ON O ^ fN »0 CN -Oh^ o*o o r^ Tf r^ o ^ o O -h o £cor- 2 CO ^ rf CN OO OnO-* CN *0 CN VOtHWI O^O r^-*^ c 3 CO Tf ^H -l-l Oh c CS J= u§ Grand Stockt Anna . io rt c rtQ O Tf LO Tf *+ >-r u •0 c n^H « rti Tf CN v£> o o o o o o o o 93.5 74.8 13.9 Till 48 8 3.6 3.1 2.3 1.1 1.4 2.4 3.2 4.0 Gumbotil 18 3.5 3.0 2.1 1.3 1.4 2.0 2.8 3.6 Loess 49, 3.7 2.9 1.8 1.2 2.1 3.1 4.9 5.0 101.3 67.5 32.7 4.6 RESULTS OF BOXDIXG TESTS Table 7. — Results of Bonding Tests — Con't. 23 Sample No. Clay percent Water percent Green com- | Dry com- pressive pressive strength strength lb. per sq. in. lib. per sq. in. Lake clays Green perme- ability 3 8 3.9 3.3 2.1 3.3 3.2 3.5 86.2 2.6 5.1 2.4 5.4 2.3 51.8 1.8 6.9 1.7 35.2 1.2 7.7 22.3 53 8 3.7 2.4 118.5 2.9 4.0 76.4 2.0 6.8 39.1 1.2 5.8 8.6 150 8 5.0 3.8 3.1 2.2 1.3 1.5 1.8 2.5 2.8 4.5 Residual clays 8 8 5.6 4.0 1.8 2.4 3.4 4.0 58.1 3.3 4.1 2.5 6.4 2.4 6.8 28.1 2.2 32.9 1.9 9.4 1.8 20.7 1.2 11.2 7.3 21 8 5.5 4.1 3.4 3.2 2.4 2.3 1.9 1.8 1.4 1.3 1.8 3.0 5.0 10.0 14.1 8.9 41.3 22.3 11.4 4.6 24 8 3.8 3.1 2.3 1.7 1.1 2.0 2.5 3.3 4.6 7.0 31 8 4.2 2.4 135.7 3.2 3.9 90.5 2.4 6.7 46.6 1.9 9.9 31.2 1.6 10.2 25.7 24 SURFACE CLAYS AS BONDING CLAYS Table 7. — Results of Bonding Tests — Con't. Sample No. Clay percent Water percent ureen com- pressive strength lb. per sq. in, Dry com- pressive strength lb. per sq. in, perme- ability Residual clays - —Concluded 44 8 5.0 1.4 3.4 2.5 101.1 3.3 2.5 2.5 4.0 54.0 2.4 4.1 2.2 47.5 2.0 6.4 1.8 30.1 1.3 20.2 1.2 8.9 50 8 3.2 3.2 49.0 2.2 5.5 26.1 1.8 8.4 14.9 1.3 6.7 4.0 52 8 4.3 3.1 42.6 3.2 5.0 30.2 2.2 9.3 17.0 1.7 11.1 8.7 1.3 7.4 Other clays 4 8 3.9 3.6 93.7 3.4 4.9 61.9 2.5 7.7 36.4 1.7 10.9 21.6 1,4 9.4 12.7 45 8 4.0 2.1 4.0 2.2 117.0 3.5 3.2 78.5 3.3 2.6 2.5 5.7 46.2 2.5 5.0 2.0 8.1 1.8 9.9 15.2 1.8 20.0 1.4 8.1 5.8 54 8 4.0 4.0 2.2 2.0 3.3 4.2 3.2 4.2 35.1 2.8 6.4 26.7 1.8 10.3 13.4 1.4 8.3 9.5 Clay concentrates 3 8 3.3 9.1 4 5.0 <10 3.9 1.4 69.9 2.9 2.7 39.7 1.9 4.1 29.0 1.0 5.5 4.6 RESULTS OF BOXDIXG TESTS 25 Table 7. — Results of Bonding Tests — Con't. Sample No. Clay percent Water percent ureen com- pressive strength lb. per sq. in. Dry com- pressive strength lb. per sq. in. Green perme- ability Clay concentrates — Concluded 18 8 3.6 14.5 4 5.2 4.1 2.0 2.6 3.4 4.2 51.2 2.8 4.7 2.1 6.9 2.0 6.0 25.9 1.1 9.0 7.0 150 8 4 3.3 4.1 15.9 2.4 3.2 4.5 40.3 3.0 4.4 2.1 7.3 19.9 1.1 8.7 7.1 Air-separated fractions, minus 0.01C mm. size 18 8 3.9 5.5 144.4 2.7 9.5 87.1 1.9 14.8 45.8 1.3 15.1 18.8 1.2 4.1 1.1 4.3 90 18 4 3.6 2.4 2.5 2.5 90.3 58.9 1.6 4.1 32.6 1.1 4.3 55 8 3.9 2.9 4.7 9.4 87.9 72.1 2.2 14.5 48.1 1.4 15.3 21.9 85 1.2 9.3 10.7 55A 8 3.9 2.8 3.2 6.0 102.3 72.8 100 95 2.0 8.7 36.5 100 1.4 9.7 20.9 90 1.1 9.2 60 56 8 3.4 5.2 134.0 2.5 8.1 86.9 1.9 12.7 55.9 1.3 15.1 33.2 85 0.9 8.4 57 8 3.9 2.6 132.7 2.9 4.1 94.5 2.3 6.2 74.7 1.3 8.9 15.9 85 1.2 7.3 10.0 58 8 3.8 2.8 5.8 11.3 78.1 46.1 2.0 17.9 29.0 1.4 15.6 13.6 85 1.0 6.8 26 SURFACE CLAYS AS BONDING CLAYS Table 7. — Results of Bonding Tests — Con't. Sample No. Clay percent Water percent Green com- pressive strength lb. per sq. in, Dry com- pressive strength lb. persq. in, Green perme- ability Air-separated fractions, minus 0.010 mm. size — Concluded 58A 8 3.8 2.7 3.8 7.5 118.3 65.5 115 115 2.1 11.1 39.9 120 1.8 12.3 33.9 130 1.4 14.2 15.2 100 1.1 10.5 70 59 8 3.9 2.7 6.7 10 6 173.9 99.7 2.1 16.8 57.7 1.4 16.4 30.5 95 1.1 12.8 12.8 59A 8 3.7 2.6 4.0 8.0 99.8 63.0 110 110 1.9 10.8 41.3 115 1.4 12.0 26.0 100 0.9 9.7 70 60 8 3.6 2.6 4.1 7.3 110.6 73.4 2.0 11.0 62.4 1.3 13.6 30.9 95 1.0 7.3 6.5 61 8 3.6 2.6 5.6 9.6 1.9 14.0 1.7 15.5 47.5 135 1.3 16.0 31.4 90 1.0 10.5 62 8 3.8 2.7 5.1 8.4 1.9 12.8 1.4 13.3 40.7 120 1.0 10.7 Air-separated fractions, minus 0.050 mm. size 18 8 3.9 2.9 2.6 4.0 147.1 101.9 2.2 6.2 55.1 1.3 8.4 16.0 1.1 7.8 6.5 55 0.9 3.6 55A 8 2.7 2.1 4.4 6.3 60.2 140 140 1.5 8.1 17.5 90 1.1 7.3 10.6 90 0.9 6.3 58A 8 2.7 2.0 3.7 6.7 65.9 39.1 140 140 1.5 10.2 23.7 100 1.1 7.7 7.4 105 0.9 3.5 RESULTS OF BONDING TESTS 27 Table 7. — Results of Bonding Tests. — Concluded. Sample No. Clay percent Water percent Green com- pressive strength lb. per sq. in. Dry com- pressive strength lb. per sq. in, perme- ability Air-separated fractions, minus 0.050 mm. size — Concluded 59 59 A. 62. 4.2 3.1 2.2 1.4 1.1 0.9 2.9 1.5 1.3 1.0 4.0 3.1 2.3 1.3 1.1 0.8 4.2 5.8 9.0 13.0 8.6 5.1 3.7 7.3 7.9 7.2 2.2 3.1 3.9 7.7 6.5 3.4 185.7 120.1 82.2 24.3 7.0 62.1 25.2 18.1 7.9 185.4 123.9 73.5 24.1 8.3 55 90 85 70 45 55 Air-separated fractions, plus 0.050 mm. size 18 20 3.8 7.3 154.3 110 2.7 11.8 88.2 120 1.9 15.6 39.8 100 1.3 6.3 21 55A 20 3.0 1.7 62.6 130 1.7 2.9 28.3 130 1.2 3.9 14.4 80 0.9 3.3 4.9 60 58A 20 3.0 2.4 92.8 90 1.6 5.5 27.4 85 1.3 6.4 14.5 75 1.0 5.5 3.6 60 59 20 3.6 7.6 178.3 130 2.6 12.2 110.6 150 1.9 17.3 61.5 120 1.3 10.5 11.2 45 59A 20 2.8 1.7 48.7 110 1.4 3.1 14.1 105 1.2 3.2 10.0 105 1.1 3.1 6.9 65 62 20 3.7 5.9 194.7 70 2.6 9.3 119.1 70 1.9 13.7 56.7 55 1.3 8.1 9.6 20 28 SURFACE CLAYS AS BONDING CLAYS ^120 Z / / // // // S* / / * // ,S : 4 6% C _AY COMMERCIAL BOND CLAYS WESTERN BENTONITE SOUTHERN BENTONITE 4% CLAY J ^ ' / / // / / * '/ 4% CLAY 12 3 4 MOISTURE (PERCENT) COMMERCIAL BENTONITES — 8(R) \\^ — 21 (R) V •- 31 (R) — 52 (R) 8% CLAY RESIDUAL CLAYS Fig. 2A. — Curves showing green and dry compressive strengths (at various moisture contents) of synthetic sands containing commercial bond clays, bentonites, and surface clays. RESULTS OF TESTS 29 GT GUMBOTIL OC OTHER CLAY L LOESS R RESIDUAL CLAY LC LAKE CLAY NB N ONBENTONITIC COMMERCIAL T TILL BONDING CLAY 1 1 24 (R) 4 4 (R) 5 (R) 1 4 (OC) 4 5 (OC) 54 (OC) l 3 (LC) 18 (GT) 48 (T) 49 ( I. ) 14 ^ z a 1 2 \ w 10 UJ ■ a. 4 2 o o z UJ o V V*. sN... 6'A C .AY 8% CI .AY 8% CLAY l I 2 3 * I 2 3 - 1 / i / // z d 100 a u ■ eod z o 60 u OC t- <0 u 40 > 10 (0 UJ E Q. 5 20 O O V tr a / i 1 / // t 1 f / / // / i / // // // / § / // // // 8% C .LAY ^ 8% CLAY '/ Q% :lay 1 2 3 « 1 2 3 * MOISTURE (PERCENT) 1 2 3 4 RESIDUAL CLAYS OTHER CLAYS TILL, GUMBOTIL AND LAKE CLAYS Fig. 2A. — Curves showing green and dry compressive strengths (at various moisture contents; of synthetic sands containing commercial bond clays, bentonites, and surface clays. 30 SURFACE CLAYS AS BONDING CLAYS I I 18 (GT) (4%) 18 (GT) 56 (GT) 60 (GT) 62 (GT) ;K ts • \ •J V \ i V V 58 58A 59 " 59A i 8% CLAY 1 'GT ) X [CTA) [GT ) (GTA) 1 I - 55 (GT ) 55A (GTA) 57 (GT ) 6 1 (GT ) / / / / / / / / / / . 1 :j 1 :/ 4 f / /// If Q% C LAY 12 3 4 12 MOISTURE (PERCENT) MINUS O.OIOMM. SIZE FRACTIONS FROM Al R - SE PAR AT ION Fig. 2B. — Curves showing green and dry compressive strengths (at various moisture contents) of synthetic sands containing air-separated fractions and clay concentrates. RESULTS OF TESTS 31 GT GUMBOTIL GTA CLAY ASSOCIATED WITH GUMBOTIL LC LAKE CLAY I I 55A (GTA) . 58A (GTA) 6 2 (GT ) / / / / / / / / / / / / . ' // f y / / / / / e% c LAY 18 (GT) 59 (GT) 59A(GTA) 6% CLAY y ' s t '2r 4% C :lay z IT W a. 2 3 4 12 3 4 MOISTURE (PERCENT) MINUS 0.050MM. SIZE FRACTIONS FROM AIR-SEPARATION CLAY CONCENTRATES Fig. 2B. — Curves showing green and dry compressive strengths (at various moisture contents) of synthetic sands containing air-separated fractions and clay concentrates. 32 SURFACE CLAYS AS BONDING CLAYS £ c 2 rt O 2 & c o C d, «-, c a b^> as cu U 3 O :- wo wo O © O O CO CN co -^ -^ ^ O wo o O wo o WO -^ Tf W-) Tt< Tf O O O O wo wo r^ oo wo so wo - uo wo wo o O O o> so r~- oo so wo wo wo O O wo wo CN ~h 0> OS ex; wo O O WO wo © wo OO OO 00 oo CQDQCQCQ Z22Z x -C C £ C tj cu co cu 3 _Q cu-O U0soor^r^s0s0'^ l '^c0coco wowoOwowoOOwoOwowoOwoOwowo fNO>ooo^oosoor^oor^wowoTtiTfco © wo O COCNrH O wo wo ■■f CO CN wo wo wo wo wo wo wo wo CO wo wo O so SO "f O wo O oo r- wo ooocoooooooooooooooooooooooooooo c u c u 5 ..::... .u -u :• -UH STRENGTH DATA 33 iolovoOOCvoOvoOOvo VO ^ OO CN rt< vo eN On 10 i— i r^ On xvonoo \DnmwO ^h co -OvOvOvO*o-^T} vo vo ^h sO NO vo vo O^^viiH OOoo^hO On r- vo vo oo vo vo vo ■D vo vo — i CO vC CO CO H r- r'rrr oooooo <<< On OC CN oo vo On VO ^h sC vo vo vo n w n e _ U to L- 3 3.3 -s-s o « = % „ O C 3 cj , c e P 34 SURFACE CLAYS AS BONDING CLAYS Table 9. — Index to Samples Sample No. Kind of clay Nearest town County 3 4 Lake Cretaceous Karnak Grand Chain Mermet Pulaski 8 Residual Massac 18 21 24 Gumbotil Residual Residual Louisville Eichorn Kampsville Clay Hardin Calhoun 31 44 45 Residual Residual Glacial Council Hill Stockton Stockton Jo Daviess Jo Daviess Jo Daviess 48 49 50 Leached till Loess Residual Chicago Heights Bartonville Eichorn Cook Peoria Hardin 52 53 54 Residual Lake Cretaceous Eichorn Harrisburg Anna Hardin Saline Union 55 55A 56 Gumbotil Gumbotil Gumbotil Marshall Marshall Montrose Clark Clark Cumberland 57 58 58A Gumbotil Gumbotil Gumbotil Toledo Brownstown Brownstown Cumberland Fayette Fayette 59 59A 60 Gumbotil Gumbotil Gumbotil Brownstown Brownstown Walnut Hill Fayette Fayette Marion 61 62 150 Gumbotil Gumbotil Lake Swanwick Kinmundy Gilberts Perry Marion Kane Table 10. — Green Compressive Strengths of Several Clays and of the Corresponding Clay Concentrates Amount of Amount of Green com- minus 0.002 mm. ground sample Moisture pressive Sample No. material in used in bond content strength sample tests percent lb. per percent percent sq. in. 3, natural 3, clay concentrate . . 18, de-pebbled....;. 18, clay concentrate . 150, natural 150, clay concentrate 35.6 100.0 8 8 3.3 3.3 3.3 9.1 31.4 100.0 8 8 3.6 3.6 1.4 14.5 35.3 100.0 8 8 3.3 3.3 2.4 15.9 STRENGTH DATA 35 > t 03 Q I w o z C/) u z p< H rn h <_> w < > * CO Ex, u Ed ft! N 0. X C co '. ) & j* oi ai Q < > Q Z < Z w w ot 1 »o CN OO to to CO £ c u CO CN OO n CO to .S " o Os to r- to Tf On r-» ON O "* bJDT3 CO C «-i rt o *-, to to CN o to to ve s indi istu CN r~- vo 1- IS CO .-. o « u ? S * E O or- ^o to vO tO Tf ~r T*H CN a c CN e- 2£ to OO — h -f ON vO ^ CN CO r 4-> O to w to O c "* ^O CN ^D CO «o uo to to C to O « •Ti <-* CO . —. co T3 o O to O O to to CN co -^ CO r> to ^o CX"" B o u c — « pS c 5 c I c mou ateri origi a u ON ON CN h> ,— 1 E S3 ON CO r> CN CO « a < 6 GO c a ex CJ c .£ ^ >s ri R *- Rl H & I. CI fc. —5 U >; e «*. £ JH £ E £ o ~. ° c C^l T3 —i w o c C S| ^ C C o -z E K c 1,1 • •— c Z s s £ 36 SURFACE CLAYS AS BONDING CLAYS ILLINOIS SURFACE CLAYS AND BENEFICIATION The data previously given on samples of various types of Illinois surface clays indi- cate that certain of them may be useful in their natural state as bonding clays whereas others require various amounts of beneficia- tion to bring them to their optimum con- dition. Although these data apply to a limit- ed number of samples it is believed that the following generalizations may be made regarding the surface clays found through- out Illinois and their need for beneficiation. Leached glacial till and gumbotil and associated clays commonly contain relatively large amounts of silt and sand plus some pebbles. In their natural state the clay mineral material in these clays, which is the effective bonding agent in them, is too dilut- ed by the sand, silt, and pebbles to produce useful bonding strengths. However, in the case of several samples studied, removal of these diluting grains down to 0.010 mm. in size leaves a clay-rich material having good to superior bonding ability. Similar treat- ment doubtless would considerably improve other clays of this general type. Thus it appears that in general the commercial use of till, gumbotil, and associated clays is apt to depend in part upon their being bene- ficiated by suitable processes to eliminate the pebbles, sand, and much of the silt. Leached loess clays are of variable com- position but usually are characterized by a relatively high silt content, a low sand con- tent and few, if any, pebbles. Here again the clay mineral material is diluted by silt and sand, and although the natural clays may be expected to give moderately high dry compressive strengths and low green compressive strengths, it is believed that the green strength would be increased by proc- essing to remove most of the silt. Leached lake clays as a rule contain no pebbles and only a relatively small amount of sand, but like loess they are high in silt. Tests on three samples show that lake clays in their natural state may be expected to impart low to medium green compressive strengths and high dry strengths. Elimina- tion of silt and sand from laboratory samples yielded a product which had green strengths comparable to the bentonites tested as a standard in this work. Thus it is believed that lake clays in general will be improved as bonding clays by the elimination of all or much of their sand and silt content. Residual clays are of diverse kinds. Some are high in clay mineral materials and may be used in the natural state for bonding clays. Others are sandy or silty and may be improved by processing to remove these diluting materials. One of the most common undesirable materials in residual clays is chert. When fragments of chert occur in important amounts their removal will facil- itate the preparation of the clay for the market and will improve the quality of the finished product. Cretaceous clays include both sandy and silty clays and also clays which are low in these constituents and therefore suitable for use as bonding clays in their natural state. The use of the varieties requiring processing would therefore seem to be un- justified. The choice of methods for beneficiating Illinois surface clays to remove nonclay substances will depend on many diverse factors. However, it is believed there exist tried methods, including pneumatic and hydraulic classification, by which the desired aims may be accomplished. APPENDIX 37 APPENDIX Description of Deposits Sampled SAMPLE 3 Lake Clay Cen. S. line SE. \/ A SW. \/ A SE. J4 sec. 26, T. 14 S., R. 2 E., Pulaski County About two miles southeast of Karnak, 5h feet of tough waxy noncalcareous silty clay from which sample 3 was taken, is exposed in the east bank of a drainage ditch known as Post Creek Cutoff. The noncalcareous clay stratum is covered by 7 to 10 feet of silt and is underlain by calcareous clay. The 7 to 10 feet of silt over- burden probably was overcast when the ditch was dug, and it is believed that the normal overburden on the noncalcareous clay is about 1 to 2 feet of silt and silty soil. A large quantity of noncalcareous clay is believed to be avail- able in adjoining areas. SAMPLE 4 Cretaceous Clav T. 14 S. Cen. S. line SW. *4 SW. % sec. 27, R. 2 E., Pulaski County In a ditch and beneath the ditch bottom along an east-west road about two miles east of Grand Chain occur the following strata: Ft. 6. Loess 8 5. Gravel, composed of chert pebbles partly cemented with iron oxide .2 4. Clay, gray and brown mottled, noncalcareous 3 3. Clay, gray, plastic, noncalcareous, lower 2 feet somewhat browner 10 2. Clay, brown, and silt, brown and yellow, interbedded, both non- calcareous 3 1. Iron crust Strata 4, 5, and 6 crop out in the sides and bottom of the ditch; strata 1, 2, and 3 were explored with a soil auger. Because stratum 4 is closely similar to stratum 3 except in color, it was mixed with the latter in the proportion of 3 parts to 10 parts to form the composite sample referred to in this report as sample 4. The clay is of Cretaceous age and crops out on the west slope of an irregular ridge which trends approximately north-south. The deposit probably caps most of the ridge, and other deposits like it may cap similar hills and ridges in the vicinity. The loess and gravel overburden is probably thickest on the crest of the ridge and thinner on its flanks. It is believed, however, that a considerably quantity of clay may be available in the vicinity of the outcrop with an average of 10 to 15 feet of overburden. SAMPLE 8 Residual Clay E. line, SE. % NE. % sec. 22, T. 14 S., R. 3 E., Massac County Red cherty clay overlying the Ste. Genevieve limestone is exposed in a cut along the Chicago, Burlington & Quincy Railroad about one mile north of Mermet. It ranges up to 3 feet in thick- ness and is overlain by 8 feet or more of loess and possibly a thin layer of brown cherty gravel. The top of the ridge to the west of the outcrop is about 25 feet above the clay exposed in the cut, and a greater thickness of clay might be revealed by exploration there. SAMPLE 18 Gumbotil SE. cor. SW. 14 NE. 14 sec. 3 5, T. 5 N., R. 6 E., Clay County In a road-cut on the east side of Panther Creek about four miles north of Louisville, 3j feet of gumbotil is exposed, from which sample 18 was taken. The gumbotil is overlain by l£ to 2 feet of soil and silt and underlain by gumbo sand. The appearance of a considerable number of additional exposures of gumbotil in the gen- eral vicinity of the sampled outcrop suggests that the upland flats of the area are probably underlain by 2 to 4 feet of gumbotil having 3 to 5 feet of overburden. A large tonnage of gumbotil appears to be available in this general area. SAMPLES 21, 50, AND 52 Residual Clays Sees. 26, 35, and 36, T. 11 S., R. 7 E., Hardin County Samples 21, 50, and 52 were all taken from the same general locality and are therefore discussed together. Sample 21 was obtained from an outcrop in the cen. S. V2 S. V2 SW. X A SE. */£ sec. 26 in a gully on the west side of State Highway 34 and 2.3 miles north of Eichorn. The strata exposed are as follows: Ft. In. Soil 6 Silt, brown, clayey; probably loess 6 Gravel, angular, brown and yellow chert 6—9 Clay, red, plastic; contains a few chert fragments (Sample 21). A yellow zone occurs about 3l feet below the top 7 Clay, mottled red and reddish brown, silty, firm; contains scattered chert fragments. . .3 Covered 38 SURFACE CLAYS AS BONDING CLAYS The deposit occurs on the north slope and some distance below the crest of a roughly east- west ridge underlain by the St. Louis limestone. As much as 5 feet of red clay may lie between the bottom of the exposed strata and the top of the underlying limestone. The thickness of the silty overburden probably increases toward the crest of the ridge. It is believed possible, how- ever, that a relatively large tonnage of clay with an overburden 10 feet thick or less may be available along the ridge. About x /4 mile southwest of the above outcrop, in the NW. % NW. hi NE. % sec. 35, sample 50 was taken from an outcrop of 62 feet of red clay that contains chert fragments, especially in its upper 3 feet. The overburden consists of 2 feet of lighter colored silty clay, followed above by a 1 foot layer of chert pebbles which is capped by 1 foot of brown silt. This sample is from the same deposit of clay as sample 21 but is not necessarily residual from the same lime- stone strata. At the outcrop limestone does not appear below the clay, but in a nearby test pit, located higher on the hillside, limestone is reported to have been encountered beneath 10 to 15 feet of red clay. Sample 52 was obtained in the NW. ^ NW. i/i NW. x /4 sec. 36 from a deposit of red clay containing chert fragments varying locally in abundance. Exposures occur in several road-cuts along the northeastern slope of a ridge. The maximum thickness of red clay observed was 6 feet, and sample 52 represents this thickness of clay. The overburden is brown silt approximate- ly 1 foot thick. The clay is believed to have been formed from the St. Louis limestone and hence to be related to the clay in the deposit from which samples 21 and 50 were obtained. Numerous outcrops of similar red clav in several gullies in the NE. M sec. 35, T. 11 S., R. 7 E., indicate that much of the surrounding area is underlain by red clay, a considerable part of which may have 10 feet or less of overburden. SAMPLE 24 Residual Clay NE. y 4 SW. V 4 SW. % sec. 4, T. 9 S., R. 2 W., Calhoun County Eight feet of cherty red clay, probably de- veloped from the Burlinton limestone, is exposed in a ditch along a gravel road west of Kamps- ville. The outcrop is in the north end of a gently sloping hill, the top of the hill being about 75 feet above the level of the outcrop. The overburden on the clay is clayey silt 3 feet or more thick. This outcrop and numerous others nearby suggest that there is a considerable quantity of similar residual clay in the area. SAMPLE 31 Residual Clay Cen. SE. V 4 SW. % sec. 30, T. 29 N., R. 2 E., Jo Daviess County At this locality 1 to 3 feet of the reddish- brown, noncherty clay underlying l£ feet of clayey silt crops out in a cut on the south side of a road. This clay is thought to have been derived from the Galena dolomite which is exposed immediately under the clay near the place where the sample was taken. The thickness of the clay probably exceeds 3 feet at places. The deposit occurs on the gently sloping east side of a ridge which trends roughly northwest. Council Hill Station on the Illinois Central Railroad is half a mile south of the sampled locality. Other deposits of the same kind of residual clay are exposed in other road-cuts in the vicinity and a considerable tonnage of clay may be available with less than 5 feet of overburden. SAMPLE 44 Residual Clay SW. cor. NW. % NE. *4 sec. 23, T. 27 N., R. 4 E., Jo Daviess County A road-cut about 70 yards long along State Highway No. 78 about lj miles south of Stockton exposes a maximum of 4 feet of red noncherty clay resting on the Galena dolomite. The overburden consists of 1 to 3 feet of soil and silt. Other outcrops in the vicinity suggest that a deposit of workable size may be present in this area. SAMPLE 45 Glacial Clay SW. 14 NW. i/4 NE. 14 sec. 3, T. 26 N., R. 4 E., Jo Daviess County About 5 miles south of Stockton on State Highway No. 78, a cut-bank along the west side of Plum River exposes the following strata: Ft. In. Soil, black 1 Clay, light yellowish-brown, calcareous 3 6 Clay, brown and dark red, non- calcareous; contains a few pebbles of worn chert (Sample 45) 4 Limestone The clay stratum from which sample 45 was taken is of uncertain origin. It may be an old glacial till from which weathering has eliminat- ed all calcareous material or possibly a water- laid clay of glacial origin. Although the extent of the deposit is not definitely known, an area of 100 acres or more situated between the main course of Plum River and the valley of Middle Fork may be underlain by noncalcareous clay of a generally similar nature. SAMPLE 48 Till NE. cor. NW. % SE. % sec. 16, T. 35 N., R. 14 E., Cook County In the bank of a ditch near Chicago Heights, 2 feet of sandy, pebbly noncalcareous till, from which sample 48 was taken, is exposed below 10 inches of soil. The noncalcareous till grades downward into calcareous till which also con- tains a greater proportion of pebbles. A large APPENDIX 39 quantity of material similar to sample 48 is available in the vicinity of the sampled locality. Samples of noncalcareous till could have been obtained at many places in northern Illinois, but the above site was selected because it is near Chicago and also near deposits of sand which may have value as molding sand but are low in natural bond. SAMPLE 49 Loess SE. % NE. % sec. 26, T. 8 N., R. 7 E, Peoria County Sample 49 was taken from an exposure half a mile southwest of Bartonville and approxi- mately 150 yards north of a main road. It represents 2 feet 8 inches of noncalcareous loess having an overburden of 1 foot of soil. Large quantities of similar loess are available. SAMPLES 51 AND 52 (See Sample 21) SAMPLE 53 Lake Clay Cen. S. V 2 SW. *4 sec. 15, T. 9 S., R. 6 E., Saline County Sample 53 was taken from 30 inches of dark gray plastic noncalcareous silty clay covered by about 1 foot of soil which was exposed in a ditch, now filled in, on the south edge of Harrisburg. At the base of the bed of noncal- careous clay is a zone 3 inches thick containing numerous nodules of impure calcium carbonate. Buff or gray calcareous silty clay lies below this zone. It is believed that the noncalcareous stratum may possibly extend over a large part of the flat area lying east and southeast of Harrisburg and that a large tonnage of this material may be available. Because of the irregular shape of the clay bodies and the possible variability in the char- acter of the clay, careful prospecting is recom- mended to determine their extent and character. The deposits are located near the Gulf Mobile and Ohio Railroad. Detailed descriptions of the occurrence and characteristics of kaolin may be found in publications of the Survey and else- where. 1 SAMPLES 55 AND 55A Gumbotil NW. V4 SW. % NW. 14 sec. 27, T. 11 N., R. 12 W., Clark County The following succession of beds is exposed in a roadcut on the north side of U. S. Highway No. 40 where it descends the east bluff of Mill Creek approximately two miles southwest of Marshall : Ft. In. Soil, bu,F, silty 1 2 Silt, gray to light buff, silty, becoming pebbly toward base 3 6 Gumbotil, gray and buff mottled, sandy, more pebbly, noncal- careous (Sample 55) 3 Till, gray and buff mottled sandy, more pebbly, noncal- careous (Sample 55A) 2 8 Till, grayish-brown, sandy, very pebbly, calcareous 15 Road level Much of the same sequence of beds is exposed in other cuts southwest along the same highway, and it is probable that gumbotil underlies siz- able areas of flat upland in the vicinity. SAMPLE 56 Gumbotil SAMPLE 54 Cretaceous Clay Sec. 35, T. 11 S., R. 2 W., Union Co. This sample is white kaolin from a commer- cial pit near Kaolin Station. The clay is prob- ably of Cretaceous age and occurs in bodies which are believed to occupy depressions in the surface of the bedrock. The deposits contain white, pink, bluish-gray, or chocolate-colored clays which are noncalcareous and plastic. Al- though in general free from impurities, the deposits locally contain lignitic material and in places layers or irregular masses of sand. The overburden is chiefly sand, gravel, and loess ranging from 5 to about 40 feet in thickness. In recent years clay has been mined commer- cially in the area by W. E. Kreitner and Kreit- ner Kaolin Co., both of Cairo, and by the South- ern Illinois Minerals Co. of Murphysboro, and by the Eastern Clay Products Co., Eifort, Ohio. Part of the Eastern Clay Products Company's production is reported to have been bonding clay. SW. 14 NW. i/4 NW. !/4 sec. 13, T. 9 N., R. 7 E., Cumberland County Sample 56 was taken from a 5-foot thickness of noncalcareous clay exposed in a cut along the east side of a road about four miles north of Montrose. Above the clay is 2 feet, 2 inches of grayish-brown silt overlain by 2 feet of buff silty soil. Below the clay is a 1— to 4— inch heavily iron-stained zone succeeded by 5 feet of grayish-brown calcareous till. It is believed that the upper 3 feet of the sampled bed is gumbotil and that the lower 2 feet is the non- calcareous clay which characteristically occurs between the gumbotil and the underlying cal- careous till. Extensive flat areas extending north and east suggest the probable existence of an abundance of material like that sampled. 1 Parmalee, C. W.. and Shroyer. C. R., Further in- vestigations of Illinois fireclays; Illinois Geol. Survey Bull. 3sD. 1921. pp. 43-63. Piersol, R. J.. Lamar. J. E.. and Voskuil, W. H., Anna "kaolin" as a new decolorizing agent for edible oils: Illinois Geol. Survey. Rept. Inv. No. 27, 1933. Grim. R. I*'... Petrology of the kaolin deposits near Anna. Illinois: Econ. Geologv, vol. 29, No. 7, Nov. 1934, pp. 659-670. 40 SURFACE CLAYS AS BONDING CLAYS SAMPLE 57 Gumbotil Near cen. S. line, SE. *4 sec. 30, T. 10 N., R. 8 E., Cumberland County A cut along the north side of State Highway No. 121 in the east bluff of a small creek about rive miles west of Toledo exposes 4 feet of gray and buff mottled silty gumbotil from which sample 57 was taken. The gumbotil is overlain by 20 inches of dark buff silt and above this 8 inches of brown sandy soil. Beneath the gum- botil appears 5 feet of very pebbly, yellow and gray, noncalcareous till and below that 3 feet of calcareous till. A large quantity of similar gumbotil probably underlies the flat areas which continue to the east and south. SAMPLES 58 AND 58A Gumbotil West line, SW. V± NW. 14 NW. V± sec. 14, T. 7 N., R. 2 E., Fayette County Samples 58 and 58A were taken from an ex- posure of glacial clay in a cut along the east side of a gravel road about four miles north of Brownstown. Ft. In. Soil, dark gray to dark buff 1 3 Gumbotil, gray and brown mottled, sandy, contains a few small pebbles (Sample 58) 2 Till, gray and brown mottled, more sandy and pebbly than the gumbotil, noncalcareous (Sample 58A) 3 Till, gray to chocolate-brown, calcareous 4± Till, brownish-gray, calcareous, hard 5 Covered Numerous other road-cuts in this vicinity show from 2 to 1\ feet of gumbotil under 1] to 2 feet of soil and silt overburden, and it appears likely that a considerable amount of gumbotil is available. (Sample 59A from upper- most Z\ feet) 4 4 Covered An extensive flat upland north of this outcrop is probably underlain by the same type of gum- botil. SAMPLE 60 Gumbotil Near cen. N. line, NW. 14 NW. V± sec. 4, T. 1 S., R. 2 E., Jefferson County Sample 60 is from 33 inches of gray silty gum- botil appearing in an outcrop on the south side of a gravel road some 50 feet west of the bridge over a shallow creek, about three miles east of Walnut Hill. The overburden consists of 20 inches of buff to gray silt overlain by 6 inches of soil. Below the gumbotil is exposed about 12 inches of noncalcareous till, browner and more pebbly than the gumbotil. The land surface east and south of the sampled outcrop is gently rolling and probably underlain by gumbotil. Outcrops visible east- ward along the road show a greater thickness of overburden, and it seems probable that the usual thickness of overburden in this general area is 4 feet or more. SAMPLE 61 Gumbotil Near cen. E. line, NE. % NE. ^ NE. 14 sec. 33 T. 4 S., R. 4 W., Perry County This outcrop is situated on the west side of a gravel road in the south valley wall of a shallow gully about 1\ miles south of Swanwick. Sample 61 represents 28 inches of mottled gray and brown pebbly gumbotil. It is overlain by 44 inches of gray to buff noncalcareous silt and 10 inches of soil. About 10 inches of noncalcareous gray till is exposed beneath the gumbotil. Similar exposures in several nearby road-cuts show about the same thickness of gumbotil under 4 to 5 feet of overburden, and it is probable that this relation exists over a sizable area. SAMPLES 59 AND 59A Gumbotil SW. ^4 SE. % NW. 1,4 sec. 14, T. 6 N., R. 2 E., Fayette County An outcrop along the east side of a gravel road in the north bluff of a small creek approxi- mately two miles south of Brownstown exposes the following beds: Ft. In. Soil, dark gray to gray 3 4 Gumbotil, brownish-gray above, mottled gray and brown be- low, sandy, pebbly (Sample 59) 2 6 Till, gray to brown, noncal- careous, more sandy and pebbly than the gumbotil SAMPLE 62 Gumbotil Cen. N. line, NW. 14 SE. V± sec. 25, T. 4 N., R. 2 E., Marion County Sample 62 was taken from 30 inches of gray pebbly gumbotil in an exposure on the south side of a gravel road near the top of the east valley wall of a shallow gully about 3h miles west-southwest of Kinmundy. From 24 to 28 inches of gray to buff soil and silt occurs above the gumbotil, and 8 inches of noncalcareous gray till succeeded by 14 inches of mixed gray and buff slightly calcareous till lies below it. Large quantities of gumbotil like sample 62 are probably available from extensive flat up- lands in the vicinity of the sampled deposit. APPENDIX 41 SAMPLE 150 Lake Clay SE. V± NW. 14 NW. V± sec. 24, T. 42 N., R. 7 E., Kane County The abandoned pit of the Walker Clay Products Co. at Gilberts exposes 2\ feet of gray and brown, noncalcareous, silty clay from which sample 150 was obtained. The overburden con- sists of 14 inches of black soil. A considerable quantity of this clay is believed to be available in the vicinity of the pit. Illinois State Geological Survey Report of Investigations No. 104 1945