Soapstone / Talc
Soapstone deposits in Arkansas were first discovered in 1888. The massive soapstone typically consists of 50 to 80 percent talc (Mg3Si4O10(OH)2) admixed with chlorite, serpentine, pyrite, quartz, calcite, magnesite, and dolomite. The rock is either massive or flaky depending on the talc and chlorite content. It is soft and has a slightly greasy or dry soapy feel when rubbed on the hands. Soapstone and talc are usually associated and are generally grouped together.
Beginning in 1953, Milwhite, Inc. operated soapstone mines at various open pits along a narrow 4-mile-long belt in northeastern Saline County and processed the rock at a grinding plant at Bryant, Saline County. The soapstone was crushed, dried, ground to a fine powder, passed through a cyclone separator, and bagged. Most Arkansas production was used as inert fillers and in vehicle brake shoes. Mine output averaged about 1,500 short tons of soapstone annually. The company permanently closed their mine and plant operations in 1999, principally due to being included as a raw materials supplier in asbestos lawsuits, even though it has never been proven that any carcinogenic mineral was a component of Arkansas soapstone.
The soapstone-serpentine deposits are probably Precambrian in age and exist as exotic lenses or masses in shale and chert beds of Ordovician age. They were most likely injected into the younger rocks by tectonic processes. Because the serpentine pinches and swells in breadth and winds sinuously, lenses of soapstone appear as isolated bodies, though in places they may join at depth. Evidence suggests that the 5 mined deposits contained more than 500,000 tons of soapstone in total initially, of which some 69,000 short tons were mined.
References
Cox, T. L., 1988, Tectonically emplaced serpentinites of the Benton uplift, Saline County, Arkansas, in Colton, G. W., ed., Proceedings of the 22nd Forum on the Geology of Industrial Minerals: Arkansas Geological Commission Miscellaneous Publication 21, p. 49-61.
Sterling, P. J., and Stone, C. G., 1961, Nickel occurrences in soapstone deposits, Saline County, Arkansas: Economic Geology, v. 56, p. 100-110.
Stone, C. G., and Sterling, P. J., 1964, Relationship of igneous activity to mineral deposits in Arkansas: Arkansas Geological Commission Miscellaneous Publication 8, 23 p.
Wicklein, P. C., 1957, Geology of the nickeliferous soapstone deposits of Saline County, Arkansas: Columbia, University of Missouri, M. S. thesis, 68 p.