Talc

Talc is named after Arabic "talq" - pure (white), probably alluding to the colour of its powder.

Talc is the world's softest mineral with the Mohs hardness 1. It can be easily scratched by a fingernail. Talc is translucent to opaque with mother-of-pearl, greasy or dull lustre.

A coarse grayish-green high-talc rock soapstone or steatite is used for carvings and ornamental objects.
General Information
Varieties/Types:
Steatite - A massive variety of Talc with a greasy feeling.
Chemical Formula
Mg
 
3
Si
 
4
O
 
10
(OH)
 
2
Ulrich Henn and Claudio C. Milisenda, Gemmological Tables (2004)
Photos of natural/un-cut material from mindat.org
Physical Properties of Talc
Mohs Hardness1 to 0
Ulrich Henn and Claudio C. Milisenda, Gemmological Tables (2004)
Specific Gravity2.55 to 2.80
Walter Schumann, Gemstones of the world (2001)
More from other references
Cleavage QualityPerfect
Ulrich Henn and Claudio C. Milisenda, Gemmological Tables (2004)
Optical Properties of Talc
Refractive Index1.539 to 1.596
Ulrich Henn and Claudio C. Milisenda, Gemmological Tables (2004)
Optical CharacterBiaxial/-
Ulrich Henn and Claudio C. Milisenda, Gemmological Tables (2004)
Birefringence0.046 to 0.050
Ulrich Henn and Claudio C. Milisenda, Gemmological Tables (2004)
Colour
Colour (General)Gray-green, pearl-white, blue-green, yellowish.
Walter Schumann, Gemstones of the world (2001)
More from other references
TransparencyTranslucent,Opaque
Walter Schumann, Gemstones of the world (2001)
More from other references
LustrePearly,Greasy,Dull
Walter Schumann, Gemstones of the world (2001)
Crystallography of Talc
Crystal SystemMonoclinic
Walter Schumann, Gemstones of the world (2001) PseudohexagonalMore from other references
Further Information
Mineral information:Talc information at mindat.org
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