UNITED STATES MINERAL RESOURCES 



TALC 



By C. Ervin Brown 



CONTENTS 



Page 



Abstract of conclusions 619 



Introduction 619 



Mineralogy and physical properties 620 



Uses 620 



Competitive minerals 621 



Exploitation 622 



Byproducts and coproducts 622 



Environmental problems 622 



Geologic environment 623 



Talc from regionally metamorphosed dolomite _- 623 

 Talc deposits formed from ultramafic and mafic 



igneous rocks 623 



Talc deposits formed by contact metamorphism of 



dolomitic sediments 624 



Resources 624 



Identified and hypothetical resources 624 



Speculative resources 624 



Prospecting techniques 625 



Problems for research 625 



References cited 625 



FIGURES 



69. Graph shoviring production and use of talc and 



soapstone in the United States, 1950-70 



70. Graph showing U.S. consumption of talc, soap- 



stone, and pyrophyllite, 1910-70 



TABLE 



128. Talc and soapstone sold or used by producers 

 in the United States, by uses 



Page 

 621 



622 



Page 

 620 



ABSTRACT OF CONCLUSIONS 



Talc as mined and used industrially is a rock containing 

 a mixture of magnesium-rich silicates and ranging in min- 

 eral composition from pure talc to predominant tremolite. 



Other minerals commonly present in talc rock are serpentine, 

 diopside, anthophyllite, and chlorite and less abundantly the 

 carbonates calcite, dolomite, and magnesite. 



Industrial talc is used in the pulverized form as a ceramic 

 base for floor and wall tile ; a paint extender ; a filler for rub- 

 ber, paper, plastics, roofing, and many other products; a 

 diluent or carrier for pesticides; and a polishing or dusting 

 agent. 



Talc is mined from metamorphosed dolomitic and quar1> 

 zose sedimentary rocks or from hydrothermally altered 

 ultramafic and mafic rocks. The main producing areas are in 

 the eastern States from New England to Alabama and 

 in the west in California, Nevada, Montana, and Texas. 



In 1969 and 1970, total consumption was over a million 

 tons — double that of 20 years ago. The projected demand 

 for the year 2,000 ranges from 2.28 to 3.36 million tons. 

 Resources of talc are large and should be adequate to meet 

 this demand, although deposits meeting the rigid chemical 

 and physical specifications of some consumer industries are 

 relatively scarce. Although all talc mining districts con- 

 tain known reserves and have a good to excellent potential 

 for the discovery of additional reserves, the great bulk of 

 reserves are in New York and Vermont. 



Most industrial areas of the United States are fairly 

 close to a source of industrial talc, except for the industries 

 of the midcontinent. There, shipping charges are a much 

 larger part of the cost of talc because most supplies are 

 shipped from Montana and Texas. Areas of metamorphic 

 rocks in Wisconsin and Michigan could contain talc de- 

 posits more favorably located for the midcontinent market. 



INTRODUCTION 



The purposes of this report are to present a cur- 

 rent picture of the resources of industrial talc in the 

 United States and to assess the potential for addi- 

 tional resources. A talc resource study by Chidester, 

 Engel, and Wright (1964) is the latest extensive 

 account giving detailed descriptions of many of the 

 talc deposits in the United States and a discussion of 

 all talc-producing districts. Subsequent studies have 

 been published for deposits in Alabama (Neathery, 

 1968; Neathery and others, 1967), California 

 (Wright, 1968), and New York (Brown, 1969). Bibli- 

 ographies of talc in the United States are available 

 in works of Engel and Wright (1960) and Merrill 



U.S. GEOL. SURVEY PROF. PAPER 820 



619 



