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| Willemite | |
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 Willemite with franklinite from New Jersey
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| General | |
| Category | Silicate mineral |
| Chemical formula | Zn2SiO4 |
| Identification | |
| Color | Colorless to white, gray, flesh-red, dark brown, honey-yellow, apple-green, blue |
| Crystal habit | Fibrous, botryoidal to massive |
| Crystal system | Trigonal Rhombohedral 33 |
| Cleavage | {0001}, {1120} - imperfect |
| Fracture | Irregular to conchoidal |
| Mohs Scale hardness | 5.5 |
| Luster | Vitreous to resinous |
| Refractive index | nω = 1.691 - 1.694 nε = 1.719 - 1.725 |
| Optical Properties | Uniaxial (+) |
| Birefringence | δ = 0.028 |
| Specific gravity | 3.9 - 4.2 |
| Diaphaneity | Transparent to opaque |
| Other Characteristics | Strongly fluorescent - may be phosphorescent |
| References | 123 |
Willemite is a zinc silicate mineral (Zn2SiO4) and a minor ore of zinc. It is highly fluorescent (green) under shortwave ultraviolet light. It occurs in all different colors in daylight, in fibrous masses, solid brown masses ("troostite"), and apple green gemmy masses. Willemite is usually formed as an alteration of previously existing sphalerite ore bodies, and is usually associated with limestone. It occurs in many places, but is best known from Arizona and the zinc, iron, manganese deposits at Franklin Furnace, New Jersey. It often occurs with red zincite (zinc oxide) and franklinite (Fe,Mn,Zn)(Fe,Mn)2O4 (an iron rich zinc mineral occurring in sharp black isometric octahedral crystals and masses). Franklinite and zincite are not fluorescent.
It was discovered in 1830 and named after William I of the Netherlands.3
See also
References
- ^ http://rruff.geo.arizona.edu/doclib/hom/willemite.pdf Handbook of Mineralogy
- ^ http://www.mindat.org/min-4292.html Mindat
- ^ a b http://webmineral.com/data/Willemite.shtml Webmineral
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Wikipedia content modification information:
- This page was last modified on 14 November 2008, at 07:27.
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