Talc

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Talc
Talc.jpg
Crystals o talc
General
CategorySilicate mineral
Formula
(repeatin unit)
Mg3Si4O10(OH)2
Strunz clessification9.EC.05
Creestal seestemmonoclinic or triclinic[1]
Space groupEither monoclinic 2m or triclinic 1[2]
Unit cella = 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]
Identification
ColourLicht tae daurk green, broun, white, gray
Creestal habitFoliatit tae fibrous masses, rare as platey tae pyramidal crystals
CleavagePerfect on {001} basal cleavage
FracturFlat surfaces (not cleavage), fractur in an uneven pattern
TenacitySectile
Mohs scale haurdness1 (definin mineral)
SkinkleWaxlike or pearly
StreakWhite tae pearl black
DiaphaneityTranslucent
Speceefic gravity2.58 tae 2.83
Optical propertiesBiaxial (-)
Refractive indexnα = 1.538 – 1.550
nβ = 1.589 – 1.594
nγ = 1.589 – 1.600
Birefringenceδ = 0.051
PleochroismWeak in dark varieties
Ultraviolet fluorescenceShort 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