UNITED STATES MINERAL RESOURCES 



DIATOMITE 



By David L. Durham 



CONTENTS 



Page 



Abstract of conclusions 191 



Introduction 191 



Uses 192 



Production 192 



Geolo^c environment 192 



Prospecting techniques 193 



Resources 194 



Problems for research 194 



References cited 194 



FIGURE 



23. Graph showing estimated diatomite produc- 

 tion, 1948-68 193 



ABSTRACT OF CONCLUSIONS 



Diatomite is a rock made of microscopic porous shells of 

 silica. Its principal domestic use is as a filtering material, for 

 purifying water and various food processing and industrial 

 fluids; other diverse uses include fillers, construction and 

 insulating materials, and mild abrasives. United States and 

 world resources of crude diatomite are adequate for the 

 foreseeable future, but the need for diatomite near markets 

 and for particular purposes encourages development of new 

 sources for the material. Studies that relate the geologic 

 setting and history of diatomite to the occurrence and prop- 

 erties of the rock can help locate important undeveloped de- 

 posits. 



INTRODUCTION 



Diatomite is a sedimentary rock composed mainly 

 of the siliceous remains of diatoms, which are 

 single-celled aquatic organisms that generally are 

 classed as algae. Diatoms depend upon a form of 

 photosynthesis; consequently they flourish only in 

 sunlit waters. They develop frustules, or shells, of 

 amorphous opaline silica (SiOa'wHaO) that com- 

 monly are complexly perforated and bear ribs, 



spines, and bristles; the combined area of holes in 

 the frustules generally ranges from 10-30 percent 

 of the total area (Lewin and Guillard, 1963, p. 378) . 

 Many valuable properties of the rock depend upon 

 the aggregate effect of the microscopically complex 

 and chemically inert diatom frustules. Papers by 

 Conger (1951), Lewin and Guillard (1963), Loh- 

 man (1960), and Patrick and Reimer (1966) in- 

 clude much general information about diatoms. 



Although the opaline silica of dead diatoms is 

 soluble in most natural waters, the rate of solution 

 is slow enough that siliceous diatom remains can 

 accumulate under favorable conditions to form the 

 substance of diatomaceous sediments and rocks. 

 Rock composed almost entirely of diatom frustules 

 generally is called diatomite; the term implies ma- 

 terial of commercial quality. Although unconsoli- 

 dated diatomaceous sediments are not properly 

 classified by the rock name "diatomite", both the 

 rock and the sediments are considered together as 

 a commodity because they both are sources of di- 

 atom products. The names "diatomaceous mud- 

 stone", "diatomaceous siltstone", and "diatomaceous 

 shale" describe rocks that contain diatom remains 

 along with a considerable amount of other sedi- 

 mentary material ; these rocks are of less commer- 

 cial interest than the more nearly pure diatomite. 

 The names "diatomaceous earth" and "kieselguhr" 

 are synonymous with the term "diatomite"; the 

 names "moler" and "moler earth" apply to impure 

 diatomite produced in Denmark. The names "infu- 

 sorial earth" and "tripoli" are used improperly for 

 diatomite. Numerous trade names identify the di- 

 atomite products of particular manufacturing com- 

 panies. Papers by Calvert (1966), Conger (1942), 

 and Lisitsyn (1967) describe the accumulation of 

 diatomaceous sediments; papers by Cummins 

 (1960), Eardley-Wilmot (1928), and Williamson 

 (1966), and an article in Industrial Minerals (1969) 

 summarize data on diatomite. 



U.S. GEOL. SURVEY PROF. PAPER 820 



191 



