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Talc investigations in Vermont, preliminary report

1951; United States Geological Survey; Linguagem: Inglês

10.3133/cir95

2332-3302

A.H. Chidester, Marland P. Billings, Wallace M. Cady,

Plant and fungal interactions

Commercial talc deposits in Vermont are derived from ultramafic igneous rocks confined chiefly.to a narrow belt that extends northward through the central part of the state from Massachusetts to Canada.This belt forms part of a more extensive belt that may be traced from Alabama to Newfoundland.It is inferred from the wide distribution of localities in which ultramafic rocks are known and the general prevalence of steatitization at those localities, that the talc reserves in Vermont are large.The geographic positions of 145 localities are indicated.Suggestions for exploration and further geologic study are made.1 A. E. J. Engel (written communication, March 29, 1950) states: *In California, for example, several economic talc deposits of appreciable size, purity, 1 and value are formed as replacements of granitic and intermediate types of igneous rock.At Natural Bridge, N.Y., also, commercial'talc' (actuaily talc and serpentine) has formed as a replacement of granite, syenite, and migmatite."2 For a definition of these terms, as used in this paper, seep.3.denseness, impermeability, and high heat-resistivity, which have made it useful to man from very early times for making pipes, ornaments, and cooking utensils.Talc has a wide variety of uses in modern industry.3/ Soapstone is sawed into crayons and pencils which are used in foundries to mark white-hot steel and in the garment ~ndustry to mark fabrics.Because "of its resistance to acids, soapstone is used extensively for laboratory tables and sinks.Its refractory properties make it suitable for molds for such materials as iron and glass.Its dielectric properties make it suitable for insulators and base plates for switchboards.The pure, dense, cryptocrystalline variety of steatite known as "lava grade" is valuable because it can be machined into intricate forms and then heat-treated to great hardness with negligible shrinkage.!/ •The soft varieties of talc which are not suitable for sawing or machining are grou...'1d to various degrees of fineness for a great variety of industrial uses.Some of the products in which ground talc is used are: paper, toilet and pharmaceutical preparations, pottery and porcelain, rope and twine, wall plaster, paints, electrical insulation, textiles, linoleum and oil cloths, soaps, roofing papers, rubber, lubricants, foundry facings, glass, agricultural insecticides, pipecoverings, leather, cement, asbestos shingles, candy, shoe polish, and crayons.Ground talc is used also to polish some articles of food, such as coffee and rice.The talc deposits of Vermont furnish varieties suitable chiefly for grinding, but small quantities of material suitable for pencils to mark structural steel are produced as a by-product.The largest producer of talc in Vermont reports the followi:q.gconsumption data, in terms of percentages of total sales, for 1949.E.!