Willemite Mineral Data

Willemite Mineral Data +

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General Willemite Information

Chemical Formula:

Zn2SiO4

Composition:

Molecular Weight = 222.86 gm

Zinc 58.68 % Zn 73.04 % ZnO

Silicon 12.60 % Si 26.96 % SiO₂

Oxygen 28.72 % O

______ ______

100.00 % 100.00 % = TOTAL OXIDE

Empirical Formula:

Zn₂(SiO₄)

Environment:

Main ore mineral at Franklin, a metamorphosed zinc orebody.

IMA Status:

Valid Species (Pre-IMA) 1830

Locality:

Franklin, Sussex Co., New Jersey, USA. Link to MinDat.org Location Data.

Name Origin:

After Willem I, King of the Netherlands (1772-1843).

Synonym:

ICSD 2425

PDF 46-1316

Troostite

Willemite Image

Images:

Willemite Conichalcite

Comments: Conichalcite with willemite.
Location: Collected from the 30 level of the Tsumeb mine. Tsumeb, Namibia. Scale: 2.1 x 1.5 cm.
© John Veevaert

Images:

Willemite

Comments: Sky blue botryoidal willemite with dark to white dolomite.
Location: Tsumeb Mine, Namibia. Scale: 6 x 3 cm.
© John Veevaert

Images:

Willemite

Comments: Specimen of blocky willemite crystals. The lower picture shows willemite under SW UV light.
Location: Franklin, New Jersey, USA. Scale: 2.8 x 2.3 cm..
© John Veevaert

Images:

Willemite Glaucochroite Zincite

Comments: Pinkish gray crystalline glaucochroite intermixed with pale green willemite, with dark red zincite and white calcite.
Location: Franklin, Sussex County, New Jersey, USA. Scale: See Photo.
© Jeff Weissman / Photographic Guide to Mineral Species

Willemite Crystallography

Axial Ratios:

a:c = 1:0.66786

Cell Dimensions:

a = 13.94, c = 9.31, Z = 18; V = 1,566.77 Den(Calc)= 4.25

Crystal System:

Trigonal - RhombohedralH-M Symbol ( 3) Space Group: R 3

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

By Intensity(I/I_o): 2.634(1), 2.834(0.95), 3.486(0.8),

Forms:

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Forms: [ 1 0 0] [ 1 1 2]

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Crystal Structure:

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Klaska K-H , Eck J C , Pohl D , Acta Crystallographica, Section B , 34 (1978) p.3324-3325, New investigation of willemite, Locality: synthetic, Note: Anisotropic displacement parameters are from ICSD

Physical Properties of Willemite

Cleavage:

[0001] Poor, [1120] Poor

Color:

White, Yellow, Green, Reddish brown, Black.

Density:

3.9 - 4.2, Average = 4.05

Diaphaniety:

Transparent to translucent to opaque

Fracture:

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

Habit:

Massive - Granular - Common texture observed in granite and other igneous rock.

Habit:

Massive - Uniformly indistinguishable crystals forming large masses.

Habit:

Prismatic - Crystals Shaped like Slender Prisms (e.g. tourmaline).

Hardness:

5.5 - Knife Blade

Luminescence:

Fluorescent, Short UV=green.

Luster:

Vitreous - Resinous

Streak:

white

Optical Properties of Willemite

Gladstone-Dale:

CI meas= -0.03 (Excellent) - where the CI = (1-KPDmeas/KC)
CI calc= 0.019 (Superior) - where the CI = (1-KPDcalc/KC)
KPDcalc= 0.1682,KPDmeas= 0.1765,KC= 0.1715

Optical Data:

Uniaxial (+), w=1.691-1.72, e=1.719-1.73, bire=0.0100-0.0280.

Calculated Properties of Willemite

Electron Density:

r_electron=4.04 gm/cc
note: r_Willemite=4.25 gm/cc.

Fermion Index

Fermion Index = 0.03008
Boson Index = 0.96992

Photoelectric:

PE_Willemite= 29.98 barns/electron
U=PE_Willemite x r_electron= 121.21 barns/cc.

Radioactivity:

GRapi = 0 (Gamma Ray American Petroleum Institute Units)

Willemite is Not Radioactive

Willemite Classification

Dana Class:

51.1.1.2 (51)Nesosilicate Insular SiO4 Groups Only

(51.1)with cations in [4] coordination

(51.1.1)Phenakite group

51.1.1.1 Phenakite Be2SiO4 R 3 3

51.1.1.2 Willemite Zn2SiO4 R 3 3

51.1.1.3 Eucryptite LiAlSiO4 R 3 3

Strunz Class:

VIII/A.01-20 VIII - Silicates

VIII/A - Nesosilicates, with [SiO4]4- groups, cations of tetrahedric orientation [4]

VIII/A.01 - Phenakite series

VIII/A.01-10 Phenakite Be2SiO4 R 3 3

VIII/A.01-20 Willemite Zn2SiO4 R 3 3

VIII/A.01-30 Eucryptite LiAlSiO4 R 3 3

Other Willemite Information

References:

NAME( Duda&Rejl90) PHYS. PROP.(Enc. of Minerals,2nd ed.,1990) OPTIC PROP.(Mason68)

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

Willemite

Zn2SiO4
Dana No: 51.1.1.2 Strunz No: VIII/A.01-20
Locality:

Notes: