Talc Mineral Data

Talc Mineral Data +

General Talc Information

Chemical Formula:

Mg3Si4O10(OH)2

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

Empirical Formula:

Mg₃Si₄O₁₀(OH)₂

Environment:

Hydrothermal alteration of non-aluminous magnesian silicates.

IMA Status:

Valid Species (Pre-IMA) 1546

Locality:

Common world wide. Link to MinDat.org Location Data.

Name Origin:

From the Arabic.

Synonym:

Kerolite

Magnesium Talc

Soapstone

Steatite - massive

Talc Image

Images:

Talc

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

Talc Crystallography

Axial Ratios:

a:b:c =0.5778:1:2.0668

Cell Dimensions:

a = 5.27, b = 9.12, c = 18.85, Z = 4; beta = 100.016° V = 892.17 Den(Calc)= 2.82

Crystal System:

Monoclinic - PrismaticH-M Symbol (2/m) Space Group: C 2/c

$Help on X Ray Diffraction:$ X Ray Diffraction:

By Intensity(I/I_o): 9.35(1), 1.53(0.55), 4.59(0.45),

Crystal Structure:

Mouse
drag1 - LMB Manipulate Structure
drag2 - RMB Resize/Rotate
Keyboard
S - Stereo Pair on/off
H - Help Screen
I - Data Info
A - Atoms On/Off
P - Polyhedra On/Off
B - Bonds On/Off
Help on Above

Gruner J W , Zeitschrift fur Kristallographie , 88 (1934) p.412-419, The crystal structures of talc and pyrophyllite, Locality: Harford County, Maryland, USA

View Additional jPOWD Structure files for Talc
[1]

Physical Properties of Talc

Cleavage:

[001] Perfect

Color:

Pale green, White, Gray white, Yellowish white, Brownish white.

Density:

2.7 - 2.8, Average = 2.75

Diaphaniety:

Translucent

Fracture:

Uneven - Flat surfaces (not cleavage) fractured in an uneven pattern.

Habit:

Foliated - Two dimensional platy forms.

Habit:

Massive - Uniformly indistinguishable crystals forming large masses.

Habit:

Scaly - Morphology like fish scales.

Hardness:

1 - Talc

Luminescence:

Fluorescent.

Luster:

Vitreous - Pearly

Streak:

white

Optical Properties of Talc

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

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.

Pleochroism (x):

colorless.

Pleochroism (y):

pale green.

Pleochroism (z):

pale green.

Calculated Properties of Talc

Electron Density:

r_electron=2.76 gm/cc
note: r_Talc=2.75 gm/cc.

Fermion Index

Fermion Index = 0.0333
Boson Index = 0.9667

Photoelectric:

PE_Talc= 1.57 barns/electron
U=PE_Talc x r_electron= 4.34 barns/cc.

Radioactivity:

GRapi = 0 (Gamma Ray American Petroleum Institute Units)

Talc is Not Radioactive

Talc Classification

Dana Class:

71.2.1.3 (71)Phyllosilicate Sheets of Six-Membered Rings

(71.2)with 2:1 Layers

(71.2.1)Pyrophyllite-talc group

71.2.1.1 Pyrophyllite Al2Si4O10(OH)2 P1 1

71.2.1.2 Ferripyrophyllite Fe2Si4O10(OH)2 C 2/m 2/m

71.2.1.3 Talc Mg3Si4O10(OH)2 C 2/c 2/m

71.2.1.4 Willemseite (Ni,Mg)3Si4O10(OH)2 C 2/c 2/m

71.2.1.5 Minnesotaite (Fe,Mg)3Si4O10(OH)2 C1 1

71.2.1.6 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

Strunz Class:

VIII/H.09-40 VIII - Silicates

VIII/H - Phyllosilicates (layered) Mica like layered silicates with [Si4O10]4- and related groups

VIII/H.09 - Talc series

VIII/H.09-10 Pyrophyllite Al2Si4O10(OH)2 P1 1

VIII/H.09-20 Ferripyrophyllite Fe2Si4O10(OH)2 C 2/m 2/m

VIII/H.09-30 Macaulayite (Fe,Al)24Si4O43(OH)2 C? Mono

VIII/H.09-40 Talc Mg3Si4O10(OH)2 C 2/c 2/m

VIII/H.09-50 Minnesotaite (Fe,Mg)3Si4O10(OH)2 C1 1

VIII/H.09-60 Willemseite (Ni,Mg)3Si4O10(OH)2 C 2/c 2/m

VIII/H.09-65 Pimelite Ni3Si4O10(OH)2·4(H2O) Unk. Hex

VIII/H.09-70 Kegelite Pb8Al4Si8O20(SO4)2(CO3)4(OH)8 A2/m,A2,Am Mono

Other Talc Information

References:

NAME( Duda&Rejl90) PHYS. PROP.(Enc. of Minerals,2nd ed.,1990) OPTIC PROP.(Heinrich65)

Search for Talc using:

[ALTAVISTA] [AOL] [About.com] [All-The-Web] [HotBot] [Ixquick] [LookSmart] [MAMMA] [MSN.COM] [Netscape] [Teoma] [Wikipedia] [YAHOO]

Visit our Advertisers for Talc :
AA Mineral Specimens
A-Rocks Auction
Adams Minerals
B and L Minerals
Dakota Matrix
Dan Weinrich Fine Minerals
Dan Weinrich Auctions
e-Rocks Auctions
Excalibur Minerals
Exceptional Minerals
Fabre Minerals
Greenside Minerals
John Betts Fine Minerals
Masons Minerals
Mineral News
Mineral of the Month Club
MineralsWeb Fine Minerals
Minernet.it
Rockshop.cz Kalat Fine Minerals
T G Fine Minerals
Wrights Rock Shop

Translate Talc Mineral Data :

Ask about Talc here :
Ask-A-Mineralogist from the Mineralogical Society of America
Mindat.org's Discussion Groups
Original Rockhounds Discussion Group
Rockhounds Discussion Group on Yahoo Groups
Mineral Discussion Forum from Fabre Minerals - also available in Español

Print or Cut-and-Paste your Talc Specimen Label here :

Talc

Mg3Si4O10(OH)2
Dana No: 71.2.1.3 Strunz No: VIII/H.09-40
Locality:

Notes: