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Crystals o talc
Category Silicate mineral
(repeatin unit)
Strunz clessification 9.EC.05
Creestal seestem monoclinic or triclinic[1]
Space group Either monoclinic 2m or triclinic 1[2]
Unit cell a = 5.291 Å, b = 9.173 Å, c = 5.290 Å; α = 98.68°, β = 119.90°, γ = 90.09°; Z = 2 or
a = 5.287 Å, b = 9.158 Å, c = 18.95 Å, β = 99.3°; Z = 4[2]
Colour Licht tae daurk green, broun, white, gray
Creestal habit Foliatit tae fibrous masses, rare as platey tae pyramidal crystals
Cleavage Perfect on {001} basal cleavage
Fractur Flat surfaces (not cleavage), fractur in an uneven pattern
Tenacity Sectile
Mohs scale haurdness 1 (definin mineral)
Skinkle Waxlike or pearly
Streak White tae pearl black
Diaphaneity Translucent
Speceefic gravity 2.58 tae 2.83
Optical properties Biaxial (-)
Refractive index nα = 1.538 – 1.550
nβ = 1.589 – 1.594
nγ = 1.589 – 1.600
Birefringence δ = 0.051
Pleochroism Weak in dark varieties
Ultraviolet fluorescence Short UV=orange yellae, lang UV=yellae
References [2][3][4]

Talc (derived frae Persie: تالکtālk; Arabic: تلكtalk) is a meeneral componed o hydrated magnesium silicate wi the chemical formula H2Mg3(SiO3)4 or Mg3Si4O10(OH)2. In loose furm, it is the widely uised substance kent as talcum pouder. It occurs as foliatit tae fibrous masses, an in an exceptionally rare crystal furm. It haes a perfect basal cleavage, an the folia are non-elastic, awtho slichtly flexible. It is the saftest kent mineral an leetit as 1 on the Mohs hairdness scale. It can be easily scratched bi a fingernail. It is an aa sectile (can be cut wi a knife). It haes a speceefic gravity o 2.5–2.8, a clear or dusty luster, an is translucent tae opaque. Talc is nae soluble in watter, but it is slichtly soluble in dilute meeneral acids. Its colour ranges frae white tae gray or green an it haes a distinctly greasy feel. Its streak is white.

Soapstone is a metamorphic rock componed predominantly o talc.

References[eedit | eedit soorce]

  1. An Introduction to the Rock-Forming Minerals, second edition, by W.A. Deer, R.A. Howie, and J. Zussman, 1992, Prentice Hall, ISBN 0-582-30094-0.
  2. 2.0 2.1 2.2 Handbook of Mineralogy
  3. Talc at Mindat.org
  4. Talc at Webmineral