- Kolata, Huff and Bergström (1996) briefly described an Ordovician K-bentonite bed at a quarry near Aylmer, Quebec (just across the river from Ottawa) noting that this bed is as much as 17 cm thick.
- Salad Hersi (1998) reported on a Bentonite layer in a roadcut at the intersection of Tenth Line Rd. and St. Joseph Blvd. in Orleans, Ontario (now part of Ottawa), within the Hull Formation about 1 meter below the base of the Verulam Formation.
- Kierman (1999) analyzed those two K-Bentonites from the Ottawa Embayment: one at the Klock Quarry in Aylmer, Quebec, and the second near the intersection of St. Joseph Blvd. and Tenth Line Rd. in Orleans, Ontario about 1 m below the base of the Verulam Formation.
- Dix and Jolicoeur ( 2011) discuss bentonite layers in the Ordovician Billings Formation and Carlsbad Formation, Eastern Ontario.
- Oruche, Dix and Kamob (2018) report on the Millbrig K-bentonite volcanic ash bed and the bentonite bed in the Hull Formation in the Ottawa embayment, tracing both across Eastern Ontario.
- Carrier (2018) reports on two bentonite layers in the Ordovician limestone at the Clark Quarry in Stittsville in the west end of Ottawa.
On August 16, 2019 I visited the outcrop at the southeast corner of the intersection of Tenth Line Road and St. Joseph Boulevard in Orleans. The K-bentonite bed is about two centimeters thick, is concordant with the underlying and overlying strata, is a chalky white colour, is recessive, has both a gritty and soapy feel, and extends over the length of the outcrop (at least 30 meters). No visible crystals are present. Many articles report that often a K-bentonite bed can be found because plants preferentially grow in the K-bentonite, and this feature was observed at this outcrop. I took the following photographs of the K-bentonite bed at that location.
Historical References to Bentonite Clay
Many early references to what we now call bentonite clay refer to it as soap clay, mineral soap, edible clay or edible earth. Selwyn (1874), for an occurrence near Edmonton mentions “Immediately above the coal seam is a layer of a brown greasy clay six or eight inches thick. This clay works into a lather like soap, and Dr. Hector says it was used by the women at the fort for washing blankets. A sample of it, analysed by Mr. Hoffmann in the Survey laboratory, shews it to be a hydrous silicate of alumina*... * For analysis of this soap-clay see Appendix.”. McConnell (1889) in a report on the Yukon and MacKenzie Basins mentions “The most interesting part of this section was under water at the time of my visit, and can only be examined in the autumn. ... The edible clay bed ... was just visible below the surface of the water, and a specimen was dug up with the paddle. This clay is of a light yellowish color, and is highly plastic. It is used for whitewashing purposes, and in former times served the Indians as a substitute for soap.” Allan and Sanderson (1945) identify Selwyn’s and McConnell’s reports as the earliest references to bentonite in Western Canada.
Condra (1908) was the first to link bentonite with volcanic ash commenting “ Professor Todd has noted the existence of a thin but very persistent layer of clay closely resembling bentonite near the middle of the Carlile formation. It varies from 1 1/2 to 3 inches thick. .. . It is suggested that it may originally have been a thin stratum of volcanic ash.” Others to make the connection were Hewitt (1917) and Wherry (1917). Keele (1920) might have been the first in Canada to write that bentonite formed from weathered volcanic rocks commenting "The clay is deposited in a flat at the base of outcrops of volcanic rocks and is evidently composed of the weathered products of these rocks" and "volcanic rocks are the source for that gelatinous clay known as bentonite."
Over the course of three papers, Professor W. C. Knight of the University of Wyoming identified novel clay deposits in Wyoming and named the clay Bentonite. In the first paper, Knight (1893) reported on large beds of ‘fire clay’ in Wyoming, specifically mentioning localities at Rock Creek station on the railroad line (from which several carloads of clay had been shipped to New York) and at Crook County where “a bank of clay has been discovered in Cretaceous rocks which has been called mineral soap or Saponite. The clay when moistened has an unctuous feeling resembling soap; but in chemical constituents it could not be classed as a mineral soap.” He also provided chemical analyses of the two clays. In the second paper, Knight (1897a) mentions that “Since the year 1888 Mr. William Taylor of Rock Creek Station,... has shipped to various parts of the United States occasional carloads of a peculiar clay , which, for convenience, may be hereafter known as “Taylorite”. ... The present quarry operated by Mr. Taylor is a quarter mile north of the railroad, but at a point further to the eastward the railroad cuts through the bed. ... When taken from the quarry it has an unctuous feeling, and when water is added , it forms an emulsion . ... Inappropriately this clay has been called ‘mineral soap’ on account of its soapy feeling in water.” In an abstract of Knight’s second paper, Spencer (1898) noted that the proposed name taylorite is “a name already in use.” In his third paper, Knight (1898) mentions that he had learned that “the name Taylorite is preoccupied; consequently it will henceforth be known as Bentonite.” and provided four analyses of Bentonite.
Interestingly, Knight’s (1893) paper has been largely overlooked. Keele (1920) is the only paper that I found referring to Knight’s first paper.
Knechtel (1952), and Hosterman and Patterson (1992,) credit Engelmann (1858) with being the first to describe the clay that we now call bentonite. This is Engelmann’s (1858, p. 511) description of clay in the Cretaceous age strata in Carbon County, Wyoming:
“Between Medicine-Bon creek and Pass creek, south of the butte, was an exposure of sandy, argillaceous slate, and above it a layer of a yellow unctuous matter, covered on the surface with an efflorescence of salts, which seemed to be a product of the decomposition of the igneous rocks. It readily imbibes water, and thereby increases much in volume and becomes plastic. An analysis of a piece which had lost most of its soluble parts gave--
Water, 18 per cent.; silica, 51 per cent. ; alumnia, 30 per cent. ; calcia, traces.
Nearer to camp 42 were similar layers; some, also, yellowish, some green, with a talcose structure. The specimens of this variety separated in the water into a light yellow stuff like the other, and in dark colored heavier particles. Analysis gave:
Water, 14 per cent.; silica, 55.5 per cent. ; alumina, 30.5 per cent.; calcia, traces.
It is, therefore, a mineral similar in its composition and properties to the bole and pimelithe. Many crystals of gypsum were disseminated through these strata, and efflorescences of salt on the surface tasted like potash or soda.”
Knechtel (1952) comments that “Engelmann's citations of bole and pimelite for comparison seem appropriate enough, in view of the stage of development of mineralogic thought in his time. In the contemporary edition of Dana’s System of Mineralogy (1854, pp. 252, 503) bole is defined as material closely resembling halloysite both in appearance an in its large content of water; “. Halloysite is an aluminosilicate clay mineral. Pimelite is a light green, somewhat greasy or waxy, smectite clay.
Intriguingly, there are many earlier papers on Fuller’s Earth, edible clay and other clays that refer to a clay that we would now call Bentonite. Not all reports of Fuller’s earth are bentonite, but many are. For example, Sir Roderick Murchison (1839) reported on layers of saponaceous clay/Fuller’s earth in the Upper Silurian rocks of Herefordshire that are now identified as bentonite (Huff, Morgan, Rundle, 1996 ). This is Sir Roderick Murchison’s (1839) report: “these flagstones are separated from the overlying Aymestry limestone, by courses of a saponaceous clay (in many instances a complete fuller's-earth) , of a yellowish white and grey colour, which is commonly known throughout Herefordshire and the adjacent counties under the name of “Walker's earth, or soap," and is sometimes used by the country people for cleansing purposes. Beds of this " Walker's earth" are not infrequent in other parts of the Upper Silurian Rocks, particularly in the Wenlock shale; and it will afterwards appear, that from their saponaceous qualities the surfaces of these beds have frequently aided the slipping of superincumbent masses of rock.” In addition, Fitton (1847) described a Fuller’s earth bed from the Isle of Wight that has now been identified as Bentonite by Ruffell et al. (2002). As well, Fitton (1836) had earlier identified a number of Fuller’s earth beds in the southeast of England that are likely bentonite (see Hallam & Sellwood, 1968; Goldring, 1999).
One of the more interesting papers that I found was by Wynne (1878), who in a report on the geology of the Salt Range in the Punjab mentions a clay-ash/decomposed rock found with volcanic rock used as soap, commenting: “Lavender Clay. The lavender clay-ash or decomposed rock found with the volcanic rock of Nilawán, &c., is used by the natives as soap or to assist in washing.” Ball’s (1881) and Watt’s (1889) comments on the fire clays, fuller’s earth and edible clays of India are also intriguing, particularly Watt’s comment (at page 362) on the “The sabún mití or soap-earth of Colgong in the Bhagalpur Division”, Bengal. Kirwan (1794) devotes pages 174 to 206 of this very early text on mineralogy to clays and earths, a few of which might be worth following up on to determine whether they can be linked to bentonite, particularly one that ‘imbibed water strongly’ and "is often of pseudo- volcanic origin, ... and perhaps also sometimes really volcanic; but it also frequently arises from the decomposition, or disintegration, of other stones." Muir's (1878) paper on an edible clay eaten by sheep in New Zealand is interesting because it contains an analysis of the clay (and not just because the sheep were eating clay), and if the clay is Bentonite would be an early British analysis of Bentonite.
A number of authors have investigated the references to Fuller’s earth and other earths used in ancient Greece, by the Roman Empire and in the Middle Ages. For example, the Cimolian earth mentioned by Pliny the Elder (AD 79) in Naturalis Historia is said to be bentonite (Beneke and Lagaly, 2002, page 64; Williams, 2013, page 254; Pabst and Koøánová, 2009, page 89) while the gray earth at Kaaden mentioned by Agricola (1546) “is the bentonite of the Rokle deposit type, the major Czech bentonite deposit of today” (Pabst and Koøánová, 2009, page 94). Robertson (1949) mentions that Pliny the Elder recorded in Book xxxv of his Natural History that the earth saxum has the property of increasing in bulk when soaked in water, and states that “the suggestion that saxum is really the first record of bentonite is strengthened by the fact that bentonite has been worked commercially in Italy on Ponza Island near Naples since 1935.” Pittinger (1975) reviewed the mineral products of the Greek island of Melos in antiquity, and concludes that alumen of Pliny the Elder “is the bentonited mined today” on Melos, while the Melian earth of Theophrastus (c. 372-322 B.C.) “could describe certain bentonitic deposits of high silica content, extensive on Melos.” Koutsopoulou , Christidis and Marantos (2016) mention that the bentonites from the Greek Island of Samos – Samian Earth – has been utilized since ancient times, but that the bentonites are mined now only at a local scale. Christidis and Scott (1993) note that “Greek bentonites have been exploited since ancient times and the clays on the island of Milos and Kimolos are mentioned by Theophrastus in his work ‘About Stones’.” However, Caley and Richards (1956, 208-9) had different interpretations for Theophrastus’ Melian earth, Kimolian earth and Samian earth.
Christopher Brett
Ottawa
References and Suggested Reading
Agricola, Georgius, 1546
De natura fossilium. Froben, Basel. [ 1955, De Natura Fossilium - Textbook of
Mineralogy . English translation by M.C. Bandy and J.A. Bandy for the Mineralogical Society of America, Special Paper 63), Geological Society of America, New York.
http://farlang.com/books/agricola-bandy-de-natura-fossilium ]
Anonymous, 1898
Mineral Soap. American Soap Journal and Perfume Gazette, volume VIII, No. 12, page 412
Anonymous, 1922
The mineral "bentonite": its occurrence and uses. Bulletin of the Imperial Institute, vol. 20, pages 344-349
https://archive.org/details/bulletinofimperi20commuoft/page/344
https://books.google.com/books/about/Bulletin.html?id=xCQzAQAAMAAJ
Anonymous, 2019a
Loxter Ashbed Quarry. Upper Ludlow Shales over massive Aymestrey Limestone with thin bentonite horizons displaying an open anticline plunging S. [Photographs of bentonite layers.]
http://www.buildingstones.org.uk/search/nprn/quarry594
Anonymous, 2019b
Whitman’s Hill Quarry - Herefordshire & Worcestershire Earth Heritage Trust. [Photographs of bentonite layers.]
http://www.earthheritagetrust.org/pub/learning-discovery/aggregates/aggregates-of-herefordshire/site-examples-hfds/whitmans-hill-quarry/
Allan, John. A. And Sanderson, J.O.G., 1945
Geology of Red Deer and Rosebud Sheets, Alberta. Res Council Alberta Report 13, 51 pages
Bentonite at pages 49-51; clay at 52
https://ags.aer.ca/publications/REP_13.html
https://ags.aer.ca/document/REP/REP_13.pdf
Beneke, Klaus and Lagaly, Gerhard, 2002
From Fuller’s Earth to Bleaching Earth: A Historical Note. ECGA (European Clay Group Association) Newsletter No.5, July 2002, page 57-78
http://www.uni-kiel.de/anorg/lagaly/group/klausSchiver/bleachingearth.pdf
Ball, V., 1881
A Manual of the Geology of India: Part III. Economic geology . Calcutta: Office of the Geological Survey of India. London: Trübner & Co. 663 pages. clay at pages 561- 571
https://books.google.ca/books?id=1pvscyOHjQcC
Caley, E.R. and J.C. Richards, 1956,
Theophrastus on Stones, Columbus: Ohio State University.
https://pdfs.semanticscholar.org/6aea/1f77da14667d90a6f6464afe4f2fdde8a6f5.pdf
Carretero, M.Isabel, 2002
Clay minerals and their beneficial effects upon human health. Applied Clay Science, Volume 21, Issues 3–4, June 2002, Pages 155-163
https://doi.org/10.1016/S0169-1317(01)00085-0
https://www.sciencedirect.com/science/article/pii/S0169131701000850
Carrier, Maureen, 2018
Geology of the Ottawa Region with Dr. Wouter Bleeker, October 13,2018 – Macnamara Field Naturalists' Club
https://mfnc.ca/geology-of-the-ottawa-region-with-dr-wouter-bleeker-october-132018/
Christidis, George and Scott, Peter W., 1993
Laboratory evaluation of bentonites. Industrial Minerals, August 1993, pages 51-57
https://www.researchgate.net/profile/GE_Christidis/publication/284127401_Laboratory_evaluation_of_bentonites/links/5671513508ae0d8b0cc2ebf0/Laboratory-evaluation-of-bentonites.pdf
Condra, G. E., 1908,
Geology and water resources of a portion of the Missouri River valley in Northeaster Nebraska: U.S. Geol. Survey Water-Supply Paper 215, 59 pages
https://pubs.er.usgs.gov/publication/wsp215
https://pubs.usgs.gov/wsp/0215/report.pdf
Eisenhour, Don D. And Brown, Richard K., 2009
Bentonite and Its Impact on Modern Life. Elements (2009) 5 (2): 83-88.
https://doi.org/10.2113/gselements.5.2.83
Engelmann, Henry, 1858,
Report of a geological exploration from Fort Leavenworth to Bryan's Pass, made in connection with the survey of a road from Fort Riley to Bridger’s Pass, under command of Lieutenant F.T. Bryan, topographic engineer, 1856, in Report of the Secretary of War, 1857: U.S. Congress, 35th, 1st session, p. 489-517.
https://books.google.ca/books?id=0YMsAAAAIAAJ
https://books.google.ca/books?id=BlBDAQAAMAAJ
Fisher, C. A., 1905
The bentonite deposits of Wyoming. In Bulletin 260 United States Geological Survey, 1905, pp 559-563
https://digital.library.unt.edu/ark:/67531/metadc944632/m1/572/?q=bentonite
Fitton, William Henry, 1824
Inquiries respecting the Geological Relations of the Beds between the Chalk and the Purbeck Limestone in the Southeast of England. [Thomson's] Annals of Philosophy for 1824, New Series, vol. viii, 365-383
https://www.biodiversitylibrary.org/item/53939#page/5/mode/1up
Fitton, William Henry, 1836
Observations on some of the Strata between the Chalk and the Oxford Oolite, in the South-east of England. [Read June 15, 1827.] Transactions of the Geological Society, 2nd Series, vol. iv. p. 103- 388 https://www.biodiversitylibrary.org/item/111668#page/121/mode/1up
Isle of Wight starts 182
Fitton , W.H. 1847.
A stratigraphical account of the section from Atherfield to Rocken-End, in the Isle of Wight.
Quarterly Journal of the Geological Society of London, 3, 289-328.
https://www.biodiversitylibrary.org/item/113687#page/427/mode/1up
Goldring, R. 1999.
Sedimentological aspects and preservation of Lower Cretaceous (Aptian) bentonites (fuller's earth) in southern England. Neues Jahrbuch fur Geologie und Palaontologie, 214, 3-24.
DOI: 10.1127/njgpa/214/1999/3
Hallam, A. & Sellwood, B.W. 1968.
Origin of fuller's earth in the Mesozoic in southern England. Nature, 220, 1193-1195.
Hewitt, D. F., 1917
The origin of bentonite and the geologic range of related materials in Bighorn, Wyoming. Journal fo the Washington. Academy of Sciences, volume 7, 196-198
https://www.biodiversitylibrary.org/item/18415#page/202/mode/1up
Hosterman, John W. and Patterson, Sam H., 1992
Bentonite and Fuller’s Earth Resources of the United States. U.S. Geological Survey Professional Paper 1522. 45 pages
https://books.google.com/books/about/U_S_Geological_Survey_Professional_Paper.html?id=bTdSAQAAMAAJ
Huff, W.D.; Morgan, D.J.; Rundle, C.C.. 1996
Silurian K-bentonites of the Welsh Borderlands : geochemistry, mineralogy and K-ar ages of illitization . Nottingham, UK, British Geological Survey. (WG/96/045) (Unpublished)
http://nora.nerc.ac.uk/id/eprint/709
Jameson, Robert, 1820
A System of Mineralogy, in which Minerals are Arranged According to the Natural History Method, Third Edition, Volume 2. Edinburgh: Archibald Constable & Co. London: Hurst, Robinson & Co. 632 pages. Fuller’s Earth at pages 300-304 https://books.google.com/books/about/A_System_of_Mineralogy_in_which_Minerals.html?id=Bc5aEjAY5dQC
Keele, J., 1915
Clay and Shale deposits of the western provinces, part 5; Keele, J. Geological Survey of Canada, Memoir no. 66, 1915, 74 pages, https://doi.org/10.4095/101562
http://ftp.maps.canada.ca/pub/nrcan_rncan/publications/ess_sst/101/101562/me_066_en.pdf
Keele, J., 1920
Ceramic Division, 153-, in Summary Report of the Mines Branch for the Calendar Year Ending December 31, 1918.
Kirwan, Richard, 1794
Elements of Mineralogy, 2nd Edition, Volume 1,
Argillaceous Genus174-206, Fuller’s Earth p. 184
https://archive.org/details/elementsmineral01kirwgoog/page/n237
Knechtel, Maxwell M., 1952
Early Ideas on Origin of Bentonite. Bulletin of the American Association of Petroleum Geologists, Volume 36, Issues 1-6, pages 884–886
https://books.google.ca/books?id=ASv0AAAAMAAJ
Knight, W. C., 1893
Geology of the Wyoming Experiment Farms, and Notes on the Mineral Resources of the State.
Bulletin No. 14 by University of Wyoming Agricultural Experiment Station, October, 1893, pages 103-211; Fire Clays at 193-4
https://repository.uwyo.edu/ag_exp_sta_bulletins/31/
Knight, W. C., 1897a
“Mineral Soap”. Engineering and Mining Journal, Volume LXIII, June 12, 1897, 600-601
https://books.google.com/books/about/Engineering_and_Mining_Journal.html?id=y3VJAQAAMAAJ
Knight, W. C., 1897b
That “Mineral Soap.” American Soap Journal and Perfume Gazette, volume VIII, No 4, page 125, July 1, 1897
Knight, W. C. , 1898
Bentonite. Engineering and Mining Journal, vol 66, October 22, 1898, p. 491
https://books.google.ca/books?id=9Jg-AQAAMAAJ
Koutsopoulou, E. ; G.E. Christidis; and I. Marantos 2016
Mineralogy, geochemistry and physical properties of bentonites from the Western Thrace Region and the islands of Samos and Chios, East Aegean, Greece. Clay Minerals (2016) 51 (4): 563-588. https://doi.org/10.1180/claymin.2016.051.4.03
Mackenzie, R.C., 1979
Clay Mineralogy - Whence and Whither? Developments in Sedimentology, Volume 27, 1979, Pages 1-14 https://doi.org/10.1016/S0070-4571(08)70696-4
https://www.sciencedirect.com/science/article/pii/S0070457108706964
McConnell, R.G., 1889
Report On An Exploration in the Yukon and MacKenzie Basins, N.W.T., 1D-161D, in Geological Survey of Canada Report of Progress 1888-89, clay at page 99D
https://archive.org/details/vol188889reporto00geol/page/n5
https://archive.org/details/vol188889reporto00geol/page/n254
Muir, M. M. Pattison, 1878
Note on an Edible Clay from New Zealand. Proceedings of the Manchester Literary and Philosophical Society, volume 17, pages 6-7
https://books.google.ca/books?id=oZ1GAQAAMAAJ
Murchison, Roderick Impey, 1839
The Silurian System. Part 1. London: John Murray. 576 pages
https://books.google.com/books/about/The_Silurian_System.html?id=jxBfAAAAcAAJ
https://www.biodiversitylibrary.org/item/165541#page/252/mode/1up
Walker’s Earth, Walker’s soap at pages 204, 249
O'Shaughnessy, W. B., 1841
Report and Correspondence on the Manufacture of an Improved Pottery from Indian Clays. The Bengal Dispensoatory and Pharmacopoeia. 18 pages
https://books.google.com/books/about/Report_and_Correspondence_on_the_Manufac.html?id=PY9eAAAAcAAJ
Pabst, Willi and Koøánová, Renata, 2009
Prehistory of clay mineralogy – from ancient times to Agricola. Acta Geodyn. Geomater., Vol. 6, No. 1 (153), 87–100, 2009
https://www.irsm.cas.cz › materialy › acta_content › 6_Pabst
Pittinger, Jill, 1975
The Mineral Products of Melos in Antiquity and Their Identification. The Annual of the British School at Athens, Vol. 70 (1975), pp. 191-197 https://www.jstor.org/stable/30103322
Pliny the Elder, written before AD 79, printed 1469
Naturalis Historia, [The Natural History, Book XXXV. An account of paintings and colours. As translated by John Bostock.
http://www.perseus.tufts.edu/hopper/text?doc=Perseus:abo:phi,0978,001:35 ]
Also: http://perseus.uchicago.edu/perseus-cgi/citequery3.pl?dbname=PerseusLatinTexts&getid=1&query=Plin.%20Nat.%2035.56
Ries, H; and Keele, J. 1913
Report on the clay and shale deposits of the western provinces, part II. Geological Survey of Canada, Memoir no. 25, 1913, 136 pages, https://doi.org/10.4095/100499
Robertson, Robert H. S., 1949
The Fuller's Earths of the Elder Pliny. The Classical Review, Volume 63, Issue 2, September 1949 , pp. 51-52 DOI: https://doi.org/10.1017/S0009840X00094749
https://www.cambridge.org/core/journals/classical-review/article/fullers-earths-of-the-elder-pliny/65D3CB6974EF87AADCC08EAE9DFAE543
Robertson, R. H. S., 1958.
The earths of Theophrastus. Classical Rev., 8: 222-223.
Ruffell, A.H., Hesselbo, S.P., Wach, G.D., Simpson, M.I. and D.S.Wray, 2002
Fuller's earth (bentonite) in the Lower Cretaceous (Upper Aptian) of Shanklin (Isle of Wight, southern England). Proceedings of the Geologists' Association, Volume 113, Issue 4, 2002, Pages 281-290. https://doi.org/10.1016/S0016-7878(02)80034-7
Selwyn, A.R.C., 1874
Observations in the North West Territory on a Journey Across the Plains from Fort Garry to Rocky Mountain House Returning by the Saskatchewan River & Lake Winnepeg. Pages 17-62, in Geological Survey of Canada Report of Progress 1873-74,
http://archive.org/stream/annualreportgeo13canagoog#page/n6/mode/2up
Spence, H. S., 1924
Bentonite. Canada Mines Branch, Publication 626, 1924, 45 pages, https://doi.org/10.4095/307808
Spencer, L.J.., 1898
[Abstract of] “Mineral Soap” By Wilbur C. Knight. Journal of the Chemical Society, London, Volume 74, Part 2, page 610
https://books.google.com/books/about/Journal_Chemical_Society_London.html?id=96MxAAAAYAAJ
Sutherland, Wayne M., 2014
Wyoming Bentonite. Summary Report. Wyoming Geological Survey. 4 pages.
https://www.wsgs.wyo.gov/products/wsgs-2014-bentonite-summary.pdf
Theophrastus, [before] 287 BC
Περὶ λίθων [Translation: on Stones], [see Caley, E.R. and J.C. Richards, 1956, Theophrastus on Stones,Columbus: Ohio State University
https://pdfs.semanticscholar.org/6aea/1f77da14667d90a6f6464afe4f2fdde8a6f5.pdf].
Watt, George, 1889
A Dictionary of the Economic Products of India - Volume 2. Calcutta, Government Printing Office, 689 pages. Clay at pages 360-367
https://archive.org/details/in.ernet.dli.2015.31092/page/n367
Wherry, Edgar. T., 1917
Clay Derived from volcanic dust in the Pierre in South Dakota. Journal of the Washington. Academy of Sciences, volume 7, 576-583
https://www.biodiversitylibrary.org/item/18415#page/582/mode/1up
Williams, Cheryll, 2013
Medicinal Plants in Australia Volume 4: An Antipodean Apothecary . New South Wales, Australia: Rosenberg Publishing, 552 pages. Page 254 Cimolian earth probably bentonite
https://books.google.com/books/about/Medicinal_Plants_in_Australia_Volume_4.html?id=7eVUAQAAQBAJ
Winer, A. A., 1954
Acid Activation Of Saskatchewan Bentonites. Saskatchewan Department of Mineral Resources. Industrial Minerals Research Branch. Report of Investigations No. 4.
8792-RPI-4_Acid_Acitvation_Of_Sask_Bentonites.pdf
Wynne, A.B., 1878
Geology of the Salt Range in the Punjab. Memoirs of the Geological Survey of India, volume 14, 313 pages, at page 300
https://books.google.ca/books?id=x2-OcwxiS74C&dq
The additional references are provided at the end of my July 28, 2019 blog posting.
