Willemseite Mineral Data

General Willemseite Information

Chemical Formula:

(Ni,Mg)3Si4O10(OH)2

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

Empirical Formula:

Ni_2.25Mg_0.75Si₄O₁₀(OH)₂

Environment:

Massive, fine-grained material.

IMA Status:

Approved IMA 1970

Locality:

Scotia talc mine, Bon Accord, Barberton district, Transvaal, South Africa. Link to MinDat.org Location Data.

Name Origin:

Named for Johannes Willemse (1909-?), geologist University of Pretoria, South Africa.

Name Pronunciation:

Willemseite + Pronunciation

Synonym:

Pimelite - (Mg, H20)

Willemseite Image

Images:

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

Images:

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

Axial Ratios:

a:b:c =0.581:1:2.076

Cell Dimensions:

a = 5.316, b = 9.149, c = 18.994, Z = 4; beta = 99.96° V = 909.87 Den(Calc)= 3.33

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/I_o): 9.4(1), 3.12(0.28), 2.503(0.23),

Physical Properties of Willemseite

Cleavage:

{001} Perfect

Color:

Light green.

Density:

3.31

Hardness:

2 - Gypsum

Streak:

greenish white

Optical Properties of Willemseite

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

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

Electron Density:

Bulk Density (Electron Density)=3.28 gm/cc
note: Specific Gravity of Willemseite =3.31 gm/cc.

Fermion Index:

Fermion Index = 0.01
Boson Index = 0.99

Photoelectric:

PE_Willemseite= 12.39 barns/electron
U=PE_Willemseite x rElectron Density= 40.60 barns/cc.

Radioactivity:

GRapi = 0 (Gamma Ray American Petroleum Institute Units)
Willemseite is Not Radioactive

Willemseite Classification

Dana Class:

71.02.01.04 (71)Phyllosilicate Sheets of Six-Membered Rings

(71.02)with 2:1 Layers

(71.02.01)Pyrophyllite-talc group

71.02.01.01 Pyrophyllite Al2Si4O10(OH)2 P1 1

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

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

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

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

71.02.01.06 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:

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

References:

NAME( Dana8) PHYS. PROP.(Enc. of Minerals,2nd ed.,1990) OPTIC PROP.(Enc. of Minerals,2nd ed.,1990)

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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Willemseite

(Ni,Mg)3Si4O10(OH)2
Dana No: 71.02.01.04 Strunz No: 09.EC.05
Locality:

Notes:

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