talc


Also found in: Dictionary, Thesaurus, Medical, Financial, Acronyms, Wikipedia.

talc,

mineral ranging in color from white through various shades of gray and green to the red and brown of impure specimens, translucent to opaque, and having a greasy, soapy feel. It is a hydrous silicate of magnesium, Mg3Si4O10(OH)2, and usually contains small quantities of nickel, iron, and aluminum as impurities. It occurs commonly in folia (thin layers), but is also found in coarsely granular, finely granular, or cryptocrystalline masses. Soapstonesoapstone
or steatite
, metamorphic rock of which the characteristic and usually chief mineral is talc, but which also contains varying parts of chlorite, mica, tremolite, quartz, magnetite, and iron compounds.
..... Click the link for more information.
, or steatite, is a massive, granular form of talc. French chalk is a fine-grained variety. Talc is usually associated with chlorite schists, serpentine, dolomite, and other metamorphic rocks; it is apparently a secondary mineral formed by the alteration of other magnesium silicates. There are important deposits of talc in Austria, Italy, France, and Canada and in the United States in California, North Carolina, Texas, Georgia, and Montana. Talc is used in making paper (as a filler), paints, face and talcum powder, soap, fireproof roofing, foundry facings, lubricants, linoleum and oilcloth, electrical insulation, and pottery.
The Columbia Electronic Encyclopedia™ Copyright © 2013, Columbia University Press. Licensed from Columbia University Press. All rights reserved. www.cc.columbia.edu/cu/cup/
The following article is from The Great Soviet Encyclopedia (1979). It might be outdated or ideologically biased.

Talc

 

a widespread mineral of the class of phyllosilicates, with the formula Mg3 [Si4O10](OH)2. The magnesium may be replaced by Fe, Ni, Al, or Cr. Varieties of talc include minnesotaite, which contains Fe (50–80 atomic percent), willemseite, which is essentially nickeliferous talc, and steatite, or soapstone, which is compact massive talc.

The crystal structure of talc is a superposition of layers about 9 angstroms thick, consisting of two silicon oxide layers with Mg and OH ions between them. The charges of the atoms in the layers are balanced, and the layers are held together only by weak van der Waals’ bonds. The symmetry of the unit cell is triclinic, but any relative displacement of the layers causes a transition to a less ordered, monoclinic structure. Talc forms foliated or compact fine-grained masses and, less frequently, irregular lamellar crystals, up to 10 cm in size, which readily break into flexible transparent lamellae along cleavage planes.

Talc may be white or various shades of green. It is soft, with a hardness of 1 on Mohs’ scale, and has a greasy feel. Its density is 2,776–2,824 kg/m3; minnesotaite has a density of 3,010 kg/m3. Although talc is formed mainly at great depths under high temperatures and pressures, crystallization is possible at the earth’s surface in a strongly alkaline medium. Commercial deposits of talc are genetically associated with ultrabasic rocks or with magnesium-carbonate rocks, such as dolomite and magnesite. Talc occurs in talcose rocks, with admixtures of carbonates or chlorite, which are formed during normal metamorphism of magnesium silicate rocks, and as the more valuable pure talcites, formed by hydrometamorphic reactions involving contact between magnesium and siliceous rocks, such as gneisses, slates, or quartzites.

In the USSR, talc is obtained from the Shabrovskii talc-magnesite and the Miass talcite deposits in the Central Urals and from the Onot steatite talc deposit in the Vostochnyi Saian. A western Baikal talc-bearing region has been discovered. Abroad, major deposits of talc exist in Canada (Madoc), the USA (Gouverneur), and France (Luzenac).

Talc is used as an extender in the rubber, paper, and paint and varnish industries. It is also used in medicine and in the perfume and cosmetics industries; in technology it is used as a solid lubricant. An important application of talc is in ceramics, especially ceramic products used in radio insulation. Nonferrous steatite talc is an ornamental stone.

REFERENCE

Mestorozhdeniia tal’ka SSSR. Moscow, 1973.
P. P. SMOLIN
Inhalation of talc dust may lead to talcosis, an illness of the pneumonoconiosis group. Talcosis is observed in workers in the talc extraction and processing industries, as well as in the perfume and rubber industries. As a rule, it is a benign, slowly progressing illness, which has little effect on general health and work capacity. The most important means for its prevention are mechanization and automation of labor, dust suppression, dust collection, and the use of respirators.

REFERENCE

Borshchevskii, Iu. M., V. G. Artamonova, and V. M. Retnev. Silikatozy i gigiena iruda. Leningrad, 1974.
The Great Soviet Encyclopedia, 3rd Edition (1970-1979). © 2010 The Gale Group, Inc. All rights reserved.

talc

[talk]
(mineralogy)
Mg3Si4O10(OH)2 A whitish, greenish, or grayish hydrated magnesium silicate mineral crystallizing in the monoclinic system; it is extremely soft (hardness is 1 on Mohs scale) and has a characteristic soapy or greasy feel.
McGraw-Hill Dictionary of Scientific & Technical Terms, 6E, Copyright © 2003 by The McGraw-Hill Companies, Inc.

talc

A soft mineral composed of hydrous magnesium silicate; a major ingredient of soapstone; used on roll roofing to prevent sticking in the roll.
McGraw-Hill Dictionary of Architecture and Construction. Copyright © 2003 by McGraw-Hill Companies, Inc.

talc

a white, grey, brown, or pale green mineral, found in metamorphic rocks. It is used in the manufacture of talcum powder and electrical insulators. Composition: hydrated magnesium silicate. Formula: Mg3Si4O10(OH)2. Crystal structure: monoclinic
Collins Discovery Encyclopedia, 1st edition © HarperCollins Publishers 2005
References in periodicals archive ?
Eastern Europe was the largest region in the global talc mining market, accounting for 42% of the market in 2018.
The author has served as a consultant toplaintiff's lawyers in asbestos and talc litigation.
While earlier talc lawsuits alleged talc itself causes ovarian cancer, plaintiffs' lawyers have more recently focused on arguing asbestos contamination in talc caused ovarian cancer and mesothelioma, a form of cancer linked to asbestos exposure.
If one looks at the science, then it is true that there are studies that show no link between talc from Johnson's baby powder and ovarian cancer and various lung ailments.
Talc is used in many cosmetics: lipstick, mascara, face powder, blush, eye shadow, foundation and even children's makeup.
Global Witness has laid out a series of suggested actions to prevent the purchasing of talc-based products resulting in money being funnelled back to these groups, including giving local communities a vested interest in the success of legitimate talc mining, strengthening border controls between the two countries, and making the supply chain more transparent so that legitimate Pakistani talc can be distinguished from imported talc front Afghanistan.
In laboratory studies, exposure of rats, mice, and hamsters to asbestos-free talc resulted in mixed findings, with tumor formation in some studies.
If J&J insists on continuing to sell talc, they should mark it with a serious warning."
Their lawyers alleged the company knew its talc was contaminated with asbestos since the 1970s but failed to warn consumers about the risks.
Mondo is an integrated producer of industrial talc additives currently owned by Advent International.
About 500,000 tonnes of talc, used in products ranging from paint to baby powder, were exported from Afghanistan in the year to March, according to Afghan mining ministry figures cited in the group's report.