TALC 



625 



1961, p. 128), although this formation at most places 

 is not metamorphosed. This area is particularly im- 

 portant as a potential source of industrial talc be- 

 cause of its proximity to the industrial areas of the 

 Middle West, which are hundreds of miles from all 

 current sources of talc. 



PROSPECTING TECHNIQUES 



Detailed geologic mapping is currently the best 

 technique in prospecting for industrial talc. For 

 deposits derived from dolomite, the stratigraphy and 

 structure must be known in order to predict the 

 occurrence of talc zones in the subsurface; for in- 

 stance, previously unknown deposits were recently 

 identified in the town of DeKalb in St. Lawrence 

 County, N.Y., through use of 1 : 12,000-scale geo- 

 logic mapping (Brown, 1969; Bannerman, 1972). 

 Although these deposits are exposed at the surface, 

 estimation of continuation to depth can only be at- 

 tempted through an understanding of the geologic 

 structure. Where talc is a product of contact meta- 

 morphism, such as along the diabase sills in the 

 southern Death Valley region, detailed knowledge 

 of the location of dolomitic sediments and diabase 

 sills is important for the location of talcose zones 

 and prediction of their continuation in the subsur- 

 face. For deposits formed from ultramafic rocks, 

 too, detailed geologic mapping is important. Geo- 

 physical methods, mainly magnetic, can be applied 

 to help locate the parent ultramafic rock. Detailed 

 geologic mapping and drilling then are needed to 

 find talcose zones. 



For most of the ceramic and filler grades of talc, 

 the consumer industries have rigid chemical and 

 physical specifications for the milled rock. Therefore, 

 after a deposit is located, considerable careful test- 

 ing of chemical and physical properties is required 

 to ascertain the minable parts of a deposit. 



PROBLEMS FOR RESEARCH 



Even though the resources of talc in the United 

 States are large, restrictive specifications of color 

 and other properties make many deposits unusable 

 for high-priced grades of talc. Sampling and labora- 

 tory testing of all known talc deposits would estab- 

 lish the quality and marketability of known re- 

 sources. As already discussed, new deposits are 

 likely to be found primarily as a result of detailed 

 mapping in geologically favorable terranes. A pro- 

 gram of concurrent field and laboratory research is 

 at present being conducted by the North Carolina 

 Department of Conservation and Development for 

 deposits in Madison County, N.C. (L. S. Wiener, 

 written commun., 1972), and a similar study re- 



cently was completed for Tallapoosa and Chamber 

 Counties, Ala. (Neathery, 1968). 



Industrial talc is an extremely versatile mineral 

 product, and new uses are continually being found. 

 Close cooperation between the research laboratories 

 of the manfacturers and those of the mining com- 

 panies could probably develop even more functional 

 grades of talc depending on the demands of new 

 products. Research on new pulverizing techniques 

 capable of producing submicron particle sizes would 

 help in opening new markets, as consumers seem to 

 desire ever finer material despite the high costs. 



High reflectance or whiteness is a required qual- 

 ity of industrial talc used in the ceramic, paint, 

 paper, and a few other industries. During the quest 

 for this higher priced product, much subgrade rock 

 is discarded. Some of the waste could be sold locally 

 for mineral filler not requiring white rock, such as 

 in rubber, roofing, insecticide, and some dusting ap- 

 plications. Some progress has apparently been made 

 in improving the color of off-white talc (Wells, 

 1970). More research in this field is needed. 



REFERENCES CITED 



[Extensive bibliographies on talc were published in 1960 (Engel and 

 Wright), 1963 (Merrill) and 1964 (Chidester and others)] 



Andrews, R. W., 1970, Wollastonite : London, Inst. Geol. 

 Sciences, Natural Environment Research Council, 114 p. 



Bannerman, H. M., 1972, Geologic map of the Richville- 

 Bigelow area, St. Lawrence County, New York: U.S. 

 Geol. Survey Misc. Geol. Inv. Map, MI-664. 



Bilbrey, J. H., 1962, Cobalt, a materials survey: U.S. Bur. 

 Mines Inf. Circ. 8103, 140 p. 



BrowTi, C. E., 1969, New talc deposit in St. Lawrence County, 

 New York: U.S. Geol. Survey Bull. 1272-D, 13 p. 



Chidester, A. H., Engel, A. E. J., and Wright, L. A., 1964, 

 Talc resources of the United States: U.S. Geol. Survey 

 Bull. 1167, 61 p. 



Chidester, A. H., and Worthington, H. W., 1962, Talc and 

 soapstone in the United States, exclusive of Alaska and 

 Hawaii: U.S. Geol. Survey Mineral Inv. Map MR-31. 



Cooper, J. D., and Hartwell, J. W., 1970, Talc, soapstone, 

 and pyrophyllite, in Mineral facts and problems: U.S. 

 Bur. Mines Bull. 650, p. 1267-1281. 



Engel, A. E. J., and Wright, L. A., 1960, Talc and soap- 

 stone, in Industrial minerals and rocks [3d ed.] : New 

 York, Am. Inst. Mining, Metall., and Petroleum Engi- 

 neers, p. 835-850. 



Espenshade, G. H., 1962, Pyrophyllite, and kyanite and re- 

 lated minerals in the United States : U.S. Geol. Survey 

 Mineral Inv. Resources Map MR-18. 



Gaskins, W. W., 1952, Historical background development 

 on use of talc in ceramic bodies : Am. Ceramic Soc. Bull., 

 V. 31, no. 10, p. 392-395. 



Hess, H. H., 1933, Hydrothermal metamorphism of an ul- 

 trabasic intrusive at Schuyler, Virginia: Am. Jour. Sci., 

 5th ser., v. 26, no. 154, p. 317. 



Industrial Minerals, 1968, Talc — Mineral with a multitude 

 of uses: Indus. Min. (London), no. 5, Feb., p. 9-16. 



