Willemite is a zinc silicate mineral () 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[
(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.")]
(it is occasionally spelled villemite).[See:
]
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From p. 71: "Bei einer Exkursion, welche ich neulich gemacht, glaube ich ein neues Mineral entdeckt zu haben; es soll Willemite heissen, nach S.M. dem König der Niederlande." (During an excursion which I made recently, I believe that I discovered a new mineral; it shall be called "Willemite", after His Majesty the King of the Netherlands.)
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[ ("... in 1829 he dedicated to the king of the Netherlands, William I, the villemite, which he had just discovered at Vieille-Montagne.")]
The troostite variety is named after Dutch-American mineralogist Gerard Troost.
Occurrence
Willemite is usually formed as an alteration of previously existing
sphalerite ore bodies, and is usually associated with
limestone. It is also found in marble and may be the result of a metamorphism of earlier
hemimorphite or
smithsonite.
[Klein, Cornelis (2007). The Manual of Mineral Science, p.484. John Wiley and Sons, Inc., Hoboken. .] Crystals have the form of hexagonal prisms terminated by rhombohedral planes: there are distinct cleavages parallel to the prism-faces and to the base. Granular and cleavage masses are of more common occurrence.
It occurs in many places, but is best known from Arizona and the zinc, iron, manganese deposits at
Franklin Furnace and Sterling Hill Mines in
New Jersey. It often occurs with red
zincite (zinc oxide) and
franklinite ( (an iron rich zinc mineral occurring in sharp black isometric octahedral crystals and masses). Franklinite and zincite are not fluorescent.
Uses
Artificial willemite was used as the basis of first-generation
fluorescent tube . When doped with manganese ions, it fluoresces with a broad white emission band. Some versions had some of the zinc replaced with
beryllium. In the 1940s it was largely replaced by second-generation halophosphors based on
fluorapatite. These, in turn have been replaced by the third-generation TriPhosphors.
See also
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List of minerals
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List of minerals named after people
External links
