Amphiboles (silicates): Talcum
Diagnostic card.
In the photo - a variety of talc - steatite. Below: a classic aggregate of talc.
Mg 3 (OH) 2 Si 4 O 10
Singonia monoclinic
Hardness 1
Specific weight 2.58-2.83
Cleavage is perfect
Crack irregular
Color is colorless, different colored
Color in powder white
Shine from fat to pearly
Talc is a magnesium silicate. Translucent in thin sheets or opaque. Colors: grayish-white, light green, brownish. The line is white. The fracture is uneven. Easy to bend, but not elastic. Cleavage is very perfect. Oily to the touch. Crystals (monoclinic syngony) are rare. Usually forms scaly aggregates. Dense aggregates, reminiscent of pork lard or stearin, are called steatite (zhirovik) or pottery stone.
Talc is the softest among the known minerals. It does not form crystals of distinct form, but occurs almost exclusively in the form of lamellar, scaly or dense aggregates. Its plates sometimes have pseudo-hexagonal outlines and perfect cleavage, reminiscent of the cleavage of mica. The color is mostly white, but can be light green or light gray.
Dense masses, called steatite (wen), are mostly greenish-gray. Talc shines through, its shine in the scales is pearl, but the massive differences are oily. It is very soft, light, scaly. Its scales are flexible, but not elastic.
Diagnostic signs.
To the touch is greasy; Does not lend itself to the action of acids and does not melt in the flame of a candle.
Origin.
This is a typically metamorphic mineral. It is formed in an atmosphere of metamorphism, characterized by average temperatures (300-400 ° C) and a large amount of water as a result of the transformation of minerals from rocks rich in magnesium and iron. It can also form in dolomite marbles having impurities.
Place of Birth.
There are large talc deposits in Austria (Styria), in the Pyrenees, in India (Madras) and in many Russian, Australian and American areas. In Italy, talc is mined in Val Chinzon and Val-Geranaska (Piedmont region), in Val Malenco (Lombardy) and Orani (Sardinia). Places of distribution: Fichtel (Germany), Saxony (Germany), Alps, Norway, Ural (CIS), USA. Sample of pcs. California, USA.
Application.
Talc is used in the production of paper; As a lubricant - in the textile industry; It is also an insulating material that is resistant to temperature changes. It is used in perfumery, in the production of paints, etc. It was previously used in medicine. Isstari is used for tailor's chalks, small sculptures, for making powder and chemist's powders.
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Poisonous and radioactive dangerous stones and minerals
** - poisonous stones and minerals (mandatory check in the chemical laboratory + explicit indication of toxicity)
** - radioactive stones and minerals (mandatory check on the standard dosimeter + ban on open sales in case of radioactivity exceeding 24 milli / g / h + additional measures of population protection)
Catalog of minerals and semi-precious stones of the world by groups
** - poisonous stones and minerals
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