Mineralogy Database

Talc Mineral Data

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General Talc Information

Help on Chemical  Formula: Chemical Formula: Mg3Si4O10(OH)2
Help on Composition: Composition: Molecular Weight = 379.27 gm
   Magnesium  19.23 %  Mg   31.88 % MgO
   Silicon    29.62 %  Si   63.37 % SiO2
   Hydrogen    0.53 %  H     4.75 % H2O
   Oxygen     50.62 %  O
             ______        ______ 
             100.00 %      100.00 % = TOTAL OXIDE
Help on Empirical Formula: Empirical Formula: Mg3Si4O10(OH)2
Help on Environment: Environment: Hydrothermal alteration of non-aluminous magnesian silicates.
Help on IMA Status: IMA Status: Valid Species (Pre-IMA) 1546
Help on Locality: Locality: Common world wide. Link to MinDat.org Location Data.
Help on Name Origin: Name Origin: From the Arabic.
Help on Name Pronunciation: Name Pronunciation: Talc Say TALC
Help on Synonym: Synonym: Kerolite
  Magnesium Talc
  Steatite - massive

Talc Image

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Comments: White Talc pseudomorphous after quartz.
Location: Johannezeche, Bavaria, Germany. Scale: Not Given.
© Lou Perloff / Photo Atlas of Minerals

Talc Crystallography

Help on Axial Ratios: Axial Ratios: a:b:c =0.5778:1:2.0668
Help on Cell Dimensions: Cell Dimensions: a = 5.27, b = 9.12, c = 18.85, Z = 4; beta = 100.016° V = 892.17 Den(Calc)= 2.82
Help on Crystal System: Crystal System: Monoclinic - Prismatic H-M Symbol (2/m) Space Group: C 2/c
Help on X Ray Diffraction: X Ray Diffraction: By Intensity(I/Io): 9.35(1), 1.53(0.55), 4.59(0.45),

Physical Properties of Talc

Help on Cleavage: Cleavage: {001} Perfect
Help on Color: Color: Pale green, White, Gray white, Yellowish white, Brownish white.
Help on Density: Density: 2.7 - 2.8, Average = 2.75
Help on Diaphaneity: Diaphaneity: Translucent
Help on Fracture: Fracture: Uneven - Flat surfaces (not cleavage) fractured in an uneven pattern.
Help on Habit: Habit: Foliated - Two dimensional platy forms.
Help on Habit: Habit: Massive - Uniformly indistinguishable crystals forming large masses.
Help on Habit: Habit: Scaly - Morphology like fish scales.
Help on Hardness: Hardness: 1 - Talc
Help on Luminescence: Luminescence: Fluorescent, Short UV=orange yellow, Long UV=yellow.
Help on Luster: Luster: Vitreous - Pearly
Help on Streak: Streak: white

Optical Properties of Talc

Help on Gladstone-Dale: Gladstone-Dale: CI meas= 0.018 (Superior) - where the CI = (1-KPDmeas/KC)
CI calc= 0.042 (Good) - where the CI = (1-KPDcalc/KC)
KPDcalc= 0.2028,KPDmeas= 0.208,KC= 0.2117
Ncalc = 1.57 - 1.6
Help on Optical Data: Optical Data: Biaxial (-), a=1.538-1.55, b=1.575-1.594, g=1.575-1.6, bire=0.0370-0.0500, 2V(Calc)=0-38, 2V(Meas)=0-30. Dispersion noticeable, r > v.
Help on Pleochroism (x): Pleochroism (x): colorless.
Help on Pleochroism (y): Pleochroism (y): pale green.

Calculated Properties of Talc

Help on Electron Density: Electron Density: Bulk Density (Electron Density)=2.76 gm/cc
note: Specific Gravity of Talc =2.75 gm/cc.
Help on Fermion Index: Fermion Index: Fermion Index = 0.03
Boson Index = 0.97
Help on Photoelectric: Photoelectric: PETalc = 1.57 barns/electron
U=PETalc x rElectron Density= 4.34 barns/cc.
Help on Radioactivity: Radioactivity: GRapi = 0 (Gamma Ray American Petroleum Institute Units)
Talc is Not Radioactive

Talc Classification

Help on  Dana Class: Dana Class: (71)Phyllosilicate Sheets of Six-Membered Rings
  (71.02)with 2:1 Layers
  (71.02.01)Pyrophyllite-talc group Pyrophyllite Al2Si4O10(OH)2 P1 1 Ferripyrophyllite Fe2Si4O10(OH)2 C 2/m 2/m Talc Mg3Si4O10(OH)2 C 2/c 2/m Willemseite (Ni,Mg)3Si4O10(OH)2 C 2/c 2/m Minnesotaite (Fe,Mg)3Si4O10(OH)2 C1 1 Brinrobertsite! (Na,K,Ca)x(Al,Fe,Mg)4(Si,Al)8O20(OH)4•3.54(H2O)[x=0.35,n=3.54] pseudo 2/m 2/m
Help on  Strunz Class: Strunz Class: 09.EC.05 09 - SILICATES (Germanates)
  09.E - Phyllosilicates
  09.EC -Phyllosilicates with mica sheets, composed of tetrahedral and octahedral nets
09.EC.05 Minnesotaite (Fe,Mg)3Si4O10(OH)2 C1 1
09.EC.05 Talc Mg3Si4O10(OH)2 C 2/c 2/m
09.EC.05 Willemseite (Ni,Mg)3Si4O10(OH)2 C 2/c 2/m

Other Talc Information

Help on See Also: See Also: Links to other databases for Talc :
1 - Am. Min. Crystal Structure Database
2 - Amethyst Galleries' Mineral Gallery
3 - Athena
4 - EUROmin Project
5 - Ecole des Mines de Paris
6 - Franklin Minerals(Dunn)
7 - Franklin Minerals(Palache)
8 - GeoScienceWorld
9 - Glendale Community College
10 - Google Images
11 - Google Scholar
12 - Handbook of Mineralogy (MinSocAm)
13 - Handbook of Mineralogy (UofA)
14 - HyperPhysics
15 - MinDAT
16 - Mineral and Gemstone Kingdom
17 - Mineralienatlas (Deutsch)
18 - Minerals in Thin Section-University of North Carolina
19 - Minerals in Thin Sections-Humboldt State
20 - Online Mineral Museum
21 - QUT Mineral Atlas
22 - Ruff.Info
23 - Scandinavian mineral gallery
24 - UCLA - Petrography Thin-Sections
26 - YupRocks

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Dana No: Strunz No: 09.EC.05





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