The Origin and Development of the Source Clays Program

William F. Moll

16 October 2002




In any clay deposit, the nature of the mineral assemblage and the composition of individual clay minerals can change radically in a few centimeters.  Consequently, any given locality can contain many subtly different types of clay minerals. Results from different laboratories on ostensible the same clay mineral may not always be comparable because the samples may indeed not contain the same clay mineral.  Such confusion slows the understanding of this important group of minerals. 


Earlier collections


The first major effort to correct the situation probably was American Petroleum Institute Project 49, under the direction of Paul F. Kerr at Columbia University in the 1940s.  The goal was to collect samples of representative clays, analyze them, and publish the results.  Ralph Holmes collected materials from a large number of localities.  The data appeared in an impressive volume (API Project 49), well known to earlier practitioners in the field. API made samples of the materials available, and later Wards Natural Science Establishment assumed responsibility in selling them. As in any pioneering project, some problems eventually appeared.  The effort did not attempt to homogenize each material.  Heterogeneity became evident.  Eventually, supplies of the most popular materials ran out.  Nevertheless, this effort proved immensely valuable in furthering clay mineral research.


CMS project development


The Clay Minerals Society involvement began in 1969, when Robert W. Rex proposed a “Reference Clay Mineral” bank to be under the auspices of the Society.  Shortly thereafter, other commitments occupied his time and the project did not proceed.  In 1970, George Brindley, who supported the idea, approached William Moll at Georgia Kaolin Company to champion it.  


Brindley and Moll considered several approaches to collect, house, and distribute such a collection. They first considered the National Bureau of Standards, which they visited in January 1971.  They decided that the NBS would not be appropriate, in part because the Society would loose control of the collection.  Moll then visited William D. Johns at the University of Missouri-Columbia in March 1971.  Johns was interested in having the collection at Missouri.  The University and the Geology Department was enthusiastic, and would develop a proposal. The University of Missouri-Columbia was particularly attractive because it had two eminent clay mineralogists, Bill Johns, and Walter Keller, as well as C.E. Marshall who also worked in clays.  Further, because of the economic importance of clay mining in Missouri, all involved believed that the Geology Department would always have a strong interest in clays.


Moll then gave a report regarding the proposed “Reference Clays” project at the CMS Council meeting in Rapid City, South Dakota, in August 1971.  The Council set up an ad hoc committee to pursue establishing such a repository.  By early 1972, Johns and the University had developed a plan.  The University agreed to provide space and facilities for storage and its accounting department to handle the billing. William D. Johns volunteered to serve as curator. The start-up costs, including containers, equipment, and a graduate student as a part-time clerk, would be $4000. 


In May 1972, H. van Olphen and Moll presented the Missouri proposal to CMS Executive Committee meeting in Washington, DC.  The Executive Committee tentatively approved it, and sent out a mail ballot to the CMS Council. After final approval by the Council, preparations began.  At the Society meeting in Woods Hole, MA, in September 1972, several industrial firms agreed to provide the samples.  Participating at this time were Lin Haden of Engelhard Corporation, John (“Spike”) Jordan of Baroid Division-National Lead Company, and Haydn Murray of Georgia Kaolin.  Jordan offered the use of the Baroid pilot plant to process the material.


Collection and processing


The firms had professional geologists carefully collect and document each sample.  Note that these industrial firms invested a great deal of time and money in collecting, processing, and delivering the materials for the Society. 



Donated by

Collection location Collection supervision

Collection date




Georgia Kaolin Co.

KGa-1: 17 km west of Sandersville, GA;    

KGa-2: 14 km north of Wrens, GA

 John Smith

4 Oct 1972

 (for both)

Wyoming bentonite


Baroid Division-

National Lead Co.

50 km west of Colony, WY Richards Rowland        

3 Oct. 1972

Texas white bentonite


Southern Clay Products Co.

10 km east of Gonzales, TX

David Christian


Cheto montmorillonite


Filtrol Corp.

10 km ESE of Sanders, AZ

Robert Secor, Robert Schwenkmeyer

late 1972



Baroid Division-

National Lead Co.

5 km south of Hector, CA.  

A.J. Higgins

Nov. 1972



Engelhard Corp.

Gadsden County, FL

Jack Wilkinson

13 Oct. 1972

Synthetic Mica-montmorillonite  Syn-1

Baroid Division-

National Lead Co.

Wallisville, TX, plant William T. Grandquist

late 1972



Each raw sample would provide one metric ton of processed material.  The decision was made to homogenize the samples. Of course some things would be lost in the homogenization process, such as the fabric of the clay.  Nevertheless, more would be gained by having a large number of units of reasonably identical materials. The processing was minimal. It included drying on steam-fired tray dryers at no greater than 100° C. Heaping into a pile, and quartering ensured an even feed into the pilot plant Raymond roller mill used for pulverization. Storage of the pulverized material was in large polyethylene bags places in paperboard drums.  The Baroid pilot plant in Houston, under the capable direction of the very experienced Harry Stuchell processed all but one of the original samples.  The Southern Clay Products plant in Gonzales, Texas, processed the Texas white montmorillonite, using a rotary dryer and Raymond roller mill, under the direction of David Christian. 




The name selected for the program was “Source Clay Minerals,” to preclude the idea that a “standard” montmorillonite, for example, exists.  In 1973, the program expanded to include other types of clays not amenable to homogenization.  The first materials were rectorite and cookeite supplied by the Arkansas Geological Commission.  These materials became the “Special Clays.”


Coding system


The coding system resulted from a request in 1973 by F. J. Flanagan at the U.S.G.S. (1974). He was preparing a compendium of research materials for the earth sciences that would include such codes.  The code included a letter for the mineral type, a letter for the locality, and a sequential number. Following this procedure, the Cheto montmorillonite code, for example, became SAz-1, signifying the first smectite sample from Arizona.


Project underway


By early 1973, all the materials had reached the University, and the program was underway. A paper presented by Moll, Johns, and van Olphen at the 1975 International Clay Conference in Mexico City described the program to an international audience.  Van Olphen and Fripiat included the materials in their “Data Handbook for Clay Minerals and other Non-Metallic Minerals” (Pergamon, 1979).  This volume gave detailed descriptions of the collection localities, as well as analytical data on the samples.




Inevitably, even a metric ton proved insufficient for the very popular materials such as SWy-1 Wyoming montmorillonite, and KGa-1 low defect (formerly “well crystallized”) kaolinite. Documentation of the original collecting sites was sufficient to enable collecting additional materials of similar characteristics. 



Donated by

Collection location     Collection supervision

Collection date

Wyoming bentonite

 SWy-2, the replacement  for   SWy-1

American Colloid Co.

Adjacent to locality of  SWy-1                   I.E. Odom

June 1993

Kaolin KGa-1b, the replacement for KGa-1

Engelhard Corporation

3 km SW of collection site of KGa-1

Robert Pruett, H.L. Webb

22 Jan. 1993


Unfortunately, the Baroid pilot plant had closed by this time.  For the Wyoming bentonite, American Colloid used a rotary dryer and a Raymond roller mill, with processing suggested by I. E. Odom. For the kaolin, A. P. Green Refractories used a blower oven for drying and a hammer mill for pulverizing, under the direction of Charles Stack. 


Continuation of the program


The program has enjoyed continual improvements over the years by adding new samples to the collection.  Recent years have seen increased public interest in safety and health. To address this interest, the Society prepared Material Safety Data Sheets for each of the materials in the repository.


Johns and Keller retired from the University of Missouri-Columbia in the late 1990’s, and the Geology Department showed declining interest in clay mineralogy.  In 2001, the Department announced it would like a new arrangement.  Jessica Kogel, president of the Society, Candice Johns, chair of the Source Clays committee, and Bill Johns, curator, decided moving the collection to a different location was best.  They and the Society considered several options, and decided to accept the offer of Cliff Johnston at Purdue University.  The collection was moved to Purdue in August 2002. 


Large numbers of people, institutions, and companies have given time and effort to make the project a success.  William D. Johns deserves much of the credit for managing the repository in his position as curator for so many years.  Moll continued to chair the committee until 1981, when James Post assumed the position.  He was able to expand the offerings greatly.  Later Jessica Elzea Kogel and now Candice Johns have served as effective chairs.