Willemite | |
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General | |
Category | Silicate mineral |
Formula (repeating unit) | Zn2SiO4 |
IMA symbol | Wlm[1] |
Strunz classification | 9.AA.05 (10 ed) 8/A.01-20 (8 ed) |
Dana classification | 51.1.1.2 |
Crystal system | Trigonal |
Crystal class | Rhombohedral (3) (same H-M symbol) |
Space group | R3 |
Identification | |
Color | Colorless to white, gray, black, flesh-red, burgundy-red, pink, brown, dark brown, mahogany-brown, honey-yellow, yellow, apple-green, blue, pastel green, light blue, azure-blue |
Crystal habit | Fibrous, botryoidal to massive |
Cleavage | {0001}, {1120} – imperfect |
Fracture | Irregular to conchoidal |
Mohs scale hardness | 5.5 |
Luster | Vitreous to resinous |
Diaphaneity | Transparent to opaque |
Specific gravity | 3.9 – 4.2 |
Optical properties | Uniaxial (+) |
Refractive index | nω = 1.691 – 1.694 nε = 1.719 – 1.725 |
Birefringence | δ = 0.028 |
Other characteristics | Strongly fluorescent; may be phosphorescent |
References | [2][3][4] |
Major varieties | |
troostite | zinc is partly replaced by manganese |
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 a variety of colors in daylight, in fibrous masses and apple-green gemmy masses. Troostite is a variant in which part of the zinc is partly replaced by manganese, it occurs in solid brown masses.
It was discovered in 1829 in the Belgian Vieille-Montagne mine. Armand Lévy was shown samples by a student at the university where he was teaching. Lévy named it after William I of the Netherlands[5] (it is occasionally spelled villemite).[6][7][8] The troostite variety is named after Dutch-American mineralogist Gerard Troost.[9]
En 1829, [Armand Lévy] décrivit la willémite [...], nouvelle espèce minérale découverte à la Vieille-Montagne à Moresnet, et la dédia à Guillaume (Willem) 1er des Pays-Bas (Lévy, 1830; Lacroix, 1919; Buttgenbach, 1947a). « Ce minéral, très-abondant à Moresnet, avait échappé à l'attention des minéralogistes qui avaient visité cette localité, lorsqu'un élève de l'université de Liége en apporta plusieurs morceaux qui me parurent appartenir à une espèce différente de celles que je connaissais; en conséquence je me rendis sur les lieux, et, après avoir mûrement examiné les nombreux échantillons que j'y rencontrai, je fus convaincu que ma conjecture était fondée » (Lévy, 1843).(Translation: "In 1829, [Lévy] described willemite, a new mineral discovered at Moresnet's Vieille-Montagne and dedicated to William I of the Netherlands. "The mineral—quite abundant in Moresnet—went unnoticed by mineralogists who had visited this location. A student of the University of Liège brought me several pieces that I was unfamiliar with, so I went to these places. After carefully examining the many samples that I came across, I was convinced that my supposition was founded.")
Syn. Wihlemite, williamsite, troostite. [...] dans les amas de calamine de la Vieille-Montagne
Ainsi s'explique qu'en 1829 il ait dédié au roi des Pays-Bas, Wilhem I, la villemite, qu'il venait de découvrir à la Vieille-Montagne.("[...] in 1829 he dedicated to the king of the Netherlands, William I, the villemite, which he had just discovered at Vieille-Montagne.")