Vermont talc

According to statistics collected by the U.S. Geological Survey (3), U.S. production of cmde talc in 1995 was 1,050,000 metric tons. Montana, Texas, Vermont, and New York were the principal producing U.S. states. Worldwide production was estimated to be 5,845,000 t. China, having 2,400,000 t, was the largest producer in the world after China and the United States, Finland, India, Brazil, France, Italy, and Canada are the next principal producers. World production of talc in 1994 is Hsted in Table 1. 

In many parts of the world, eg, China and northern Canada, block talc is used by the native artisans as a carving material and some of the sculptures produced ate widely treasured. Block talc is also used for manufacture of fireplaces in Finland and Vermont. Machined talc pencils have been used for marking steel during processing since the 1890s. 

It is found chiefly in the metamorphic rocks, often those of a more basic type due to the alteration of the minerals above mentioned. Some localities are the Austrian Tyrol, the St. Gotthard district of Switzerland, Bavaria and Cornwall, England. In Canada, talc is found in Brome County, Quebec and Hastings County, Ontario, In tire United States, well-known localities are to be found in Vermont, New Hampshire, Massachusetts, Rhode Island, New York, Pennsylvania. Maryland, and North Carolina,... 

The talc/magnesite variety of ores are derived from serpentinite hosts and are typically found in Vermont, Quebec, and Finland. This type of ore is macrocrystalline in nature and composed of approximately 45-65% talc by weight, with the remainder of the ore made up of magnesite (magnesium carbonate). In some low-cost applications, such as automotive underhood, these ores are coarsely ground and used as is. These ores are also frequently beneficiated to 93-99 wt% talc by flotation. Because talc is hydrophobic, it is easy to float with surfactants. The talc floats on an aqueous bubble, whereas the co-mineral impurities sink in the water phase. 

TALC. 3Mg0-4Si02-H20. Talc is a hydrous magnesium silicate, with the composition 63.4% SiOj, 31.9% MgO and 4.7% HjO when found in pure form. It is an extremely soft mineral with a Mohs hardness of 1, has a platy structure and it is naturally hydro-phobic. Talc occurs as a relatively pure massive mineral in Montana, Australia and China. Elsewhere it occurs in conjunction with magnesite (Vermont, Quebec, Ontario and Finland), with tremoUte and serpentine in New York and with chlorite in France and Austria. In many ceramic applications, the presence of non-talc minerals such as chlorite and tremolite are beneficial. 

Talc is mined and produced in large quantities in the United States (mostly in Montana, New York, Texas, and Vermont). Talc is also found in abundance in Canada, China, Japan, the Italian Alps, the French Pyrenees, Russia, Brazil, and South Korea. The supply of talc is rather large and is projected to meet the growth in demand. 

Vermont talc - Most crude Vermont talc is characterized by a significant content, 20-30%, of magnesite. The ore is beneficiated to produce products containing various amounts of residual magnesite and occasionally other carbonates, mainly for filler applications. High-purity cosmetic- and pharmaceutical-grade floated talc has been produced in Vermont as well. 

Figure 15. Differential thermal curves for talc samples from A— Vermont, U.S.A. B— Tijola, Spain C—Darnius, Spain (contaminated with dolomite) D—Masanet, Spain (contaminated with clilorite and/or magnesite) E—same locality, after treatment with 3 N HCl for 4 hr (Munoz Taboadela and Aleixandre Ferrandis [1957]).

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