Willemite Mineral Data

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).

Name Pronunciation:

Willemite + Pronunciation

Synonym:

ICSD 2425

PDF 46-1316

Troostite

Willemite Image

Images:

Conichalcite Willemite

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:

Glaucochroite Zincite Willemite

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 - Rhombohedral H-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),

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Forms: ( 1 0 0) ( 1 1 2)

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Physical Properties of Willemite

Cleavage:

{0001} Poor, {1120} Poor

Color:

White, Yellow, Green, Reddish brown, Black.

Density:

3.9 - 4.2, Average = 4.05

Diaphaneity:

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 and phosphorescent, Short UV=green, Long 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
Ncalc = 1.67 - 1.73

Optical Data:

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

Calculated Properties of Willemite

Electron Density:

Bulk Density (Electron Density)=4.04 gm/cc
note: Specific Gravity of Willemite =4.25 gm/cc.

Fermion Index:

Fermion Index = 0.03
Boson Index = 0.97

Photoelectric:

PE_Willemite= 29.98 barns/electron
U=PE_Willemite x rElectron Density= 121.21 barns/cc.

Radioactivity:

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

Willemite Classification

Dana Class:

51.01.01.02 (51)Nesosilicate Insular SiO4 Groups Only

(51.01)with cations in [4] coordination

(51.01.01)Phenakite group

51.01.01.01 Phenakite Be2SiO4 R 3 3

51.01.01.02 Willemite Zn2SiO4 R 3 3

51.01.01.03 Eucryptite LiAlSiO4 R 3 3

Strunz Class:

09.AA.05 09 - SILICATES (Germanates)

09.A - Nesosilicates

09.AA -Nesosilicates without additional anions;

09.AA.05 Eucryptite LiAlSiO4 R 3 3

09.AA.05 Phenakite Be2SiO4 R 3 3

09.AA.05 Willemite Zn2SiO4 R 3 3

Other Willemite Information

References:

NAME( Duda&Rejl90) PHYS. PROP.(Enc. of Minerals,2nd ed.,1990;www.saint-hilaire.ca) OPTIC PROP.(Mason68)

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

Willemite

Zn2SiO4
Dana No: 51.01.01.02 Strunz No: 09.AA.05
Locality:

Notes:

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