Mineralogy Database

Willemseite Mineral Data

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General Willemseite Information

Help on Chemical  Formula: Chemical Formula: (Ni,Mg)3Si4O10(OH)2
Help on Composition: Composition: Molecular Weight = 456.63 gm
   Magnesium   3.99 %  Mg    6.62 % MgO
   Silicon    24.60 %  Si   52.63 % SiO2
   Nickel     28.92 %  Ni   36.80 % NiO
   Hydrogen    0.44 %  H     3.95 % H2O
   Oxygen     42.05 %  O
             ______        ______ 
             100.00 %      100.00 % = TOTAL OXIDE
Help on Empirical Formula: Empirical Formula: Ni2.25Mg0.75Si4O10(OH)2
Help on Environment: Environment: Massive, fine-grained material.
Help on IMA Status: IMA Status: Approved IMA 1970
Help on Locality: Locality: Scotia talc mine, Bon Accord, Barberton district, Transvaal, South Africa. Link to MinDat.org Location Data.
Help on Name Origin: Name Origin: Named for Johannes Willemse (1909-?), geologist University of Pretoria, South Africa.
Help on Name Pronunciation: Name Pronunciation: Willemseite + Pronunciation Say WILLEMSEITE
Help on Synonym: Synonym: Pimelite - (Mg, H20)

Willemseite Image

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  Trevorite   Willemseite

Comments: Small trevorite crystal in massive willemseite.
Location: Bon Accord, Barberton Mountain, Mpumalanga, South Africa. Scale: See Photo.
© Jeff Weissman / Photographic Guide to Mineral Species

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  Willemseite   Trevorite

Comments: Waxy translucent green willemseite with black trevorite in schistose rock.
Location: Near Scotia Talc Mine, Barberton Mountain, Transvaal, Mpumalanga, South Africa. Scale: See Photo.
© Jeff Weissman / Photographic Guide to Mineral Species

Willemseite Crystallography

Help on Axial Ratios: Axial Ratios: a:b:c =0.581:1:2.076
Help on Cell Dimensions: Cell Dimensions: a = 5.316, b = 9.149, c = 18.994, Z = 4; beta = 99.96° V = 909.87 Den(Calc)= 3.33
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): 9.4(1), 3.12(0.28), 2.503(0.23),

Physical Properties of Willemseite

Help on Cleavage: Cleavage: {001} Perfect
Help on Color: Color: Light green.
Help on Density: Density: 3.31
Help on Hardness: Hardness: 2 - Gypsum
Help on Streak: Streak: greenish white

Optical Properties of Willemseite

Help on Gladstone-Dale: Gladstone-Dale: CI meas= 0.044 (Good) - where the CI = (1-KPDmeas/KC)
CI calc= 0.05 (Good) - where the CI = (1-KPDcalc/KC)
KPDcalc= 0.1909,KPDmeas= 0.192,KC= 0.2009
Ncalc = 1.66 - 1.67
Help on Optical Data: Optical Data: Biaxial (-), a=1.6, b=1.652, g=1.655, bire=0.0550, 2V(Calc)=26, 2V(Meas)=27.

Calculated Properties of Willemseite

Help on Electron Density: Electron Density: Bulk Density (Electron Density)=3.28 gm/cc
note: Specific Gravity of Willemseite =3.31 gm/cc.
Help on Fermion Index: Fermion Index: Fermion Index = 0.01
Boson Index = 0.99
Help on Photoelectric: Photoelectric: PEWillemseite = 12.39 barns/electron
U=PEWillemseite x rElectron Density= 40.60 barns/cc.
Help on Radioactivity: Radioactivity: GRapi = 0 (Gamma Ray American Petroleum Institute Units)
Willemseite is Not Radioactive

Willemseite 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 Willemseite Information

Help on References: References: NAME( Dana8) PHYS. PROP.(Enc. of Minerals,2nd ed.,1990) OPTIC PROP.(Enc. of Minerals,2nd ed.,1990)
Help on See Also: See Also: Links to other databases for Willemseite :
1 - Am. Min. Crystal Structure Database
2 - Athena
3 - EUROmin Project
4 - Ecole des Mines de Paris
5 - GeoScienceWorld
6 - Google Images
7 - Google Scholar
8 - Handbook of Mineralogy (MinSocAm)
9 - Handbook of Mineralogy (UofA)
10 - MinDAT
11 - Mineralienatlas (Deutsch)
12 - Online Mineral Museum
13 - QUT Mineral Atlas
14 - Ruff.Info

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Dana No: Strunz No: 09.EC.05





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