Willemite is a

zinc Zinc is a chemical element with the symbol Zn and atomic number 30. Zinc is a slightly brittle metal at room temperature and has a shiny-greyish appearance when oxidation is removed. It is the first element in group 12 (IIB) of the periodi ...

silicate mineral Silicate minerals are rock-forming minerals made up of silicate groups. They are the largest and most important class of minerals and make up approximately 90 percent of Earth's crust. In mineralogy, silica (silicon dioxide, ) is usually consid ...

() and a minor ore of

. It is highly

fluorescent Fluorescence is the emission of light by a substance that has absorbed light or other electromagnetic radiation. It is a form of luminescence. In most cases, the emitted light has a longer wavelength, and therefore a lower photon energy, ...

(green) under shortwave

ultraviolet Ultraviolet (UV) is a form of electromagnetic radiation with wavelength from 10 nm (with a corresponding frequency around 30 PHz) to 400 nm (750 THz), shorter than that of visible light, but longer than X-rays. UV radiation ...

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 Manganese is a chemical element with the symbol Mn and atomic number 25. It is a hard, brittle, silvery metal, often found in minerals in combination with iron. Manganese is a transition metal with a multifaceted array of industrial alloy use ...

, it occurs in solid brown masses. It was discovered in 1829 in the Belgian

Vieille-Montagne Vieille Montagne was a zinc mine in Kelmis (La Calamine), a town in Belgium between Liège and Aachen. The mine's name is French for "old mountain", and this is also reflected in its German name, (earlier, ). The mine was once a bone of contenti ...

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 William I (Willem Frederik, Prince of Orange-Nassau; 24 August 1772 – 12 December 1843) was a Prince of Orange, the King of the Netherlands and Grand Duke of Luxembourg. He was the son of the last Stadtholder of the Dutch Republic, who went ...

(it is occasionally spelled villemite). The troostite variety is named after Dutch-American mineralogist Gerard Troost.

Occurrence

Willemite 2 variety troostite zinc orthosilicate Franklin Sussex County New Jersey 1907

Willemite is usually formed as an alteration of previously existing sphalerite ore bodies, and is usually associated with

limestone Limestone ( calcium carbonate ) is a type of carbonate sedimentary rock which is the main source of the material lime. It is composed mostly of the minerals calcite and aragonite, which are different crystal forms of . Limestone forms whe ...

. It is also found in marble and may be the result of a metamorphism of earlier

hemimorphite Hemimorphite is the chemical compound Zn4( Si2O7)( OH)2 ·H2O, a component of mineral calamine. It is a silicate mineral which, together with smithsonite (ZnCO3), has been historically mined from the upper parts of zinc and lead ores. Both ...

smithsonite Smithsonite, also known as zinc spar, is the mineral form of zinc carbonate ( Zn CO3). Historically, smithsonite was identified with hemimorphite before it was realized that they were two different minerals. The two minerals are very similar in a ...

. 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 Franklin may refer to: People * Franklin (given name) * Franklin (surname) * Franklin (class), a member of a historical English social class Places Australia * Franklin, Tasmania, a township * Division of Franklin, federal electoral d ...

and

Sterling Hill Mine The Sterling Hill Mine, now known as the Sterling Hill Mine Tour & Museum of Fluorescence, is a former iron and zinc mine in Ogdensburg, Sussex County, New Jersey, United States. It was the last working underground mine in New Jersey when it c ...

s in

New Jersey New Jersey is a state in the Mid-Atlantic and Northeastern regions of the United States. It is bordered on the north and east by the state of New York; on the east, southeast, and south by the Atlantic Ocean; on the west by the Delaware ...

. It often occurs with red

zincite Zincite is the mineral form of zinc oxide ( Zn O). Its crystal form is rare in nature; a notable exception to this is at the Franklin and Sterling Hill Mines in New Jersey, an area also famed for its many fluorescent minerals. It has a hexagon ...

(zinc oxide) and

franklinite Franklinite is an oxide mineral belonging to the normal spinel subgroup's iron (Fe) series, with the formula ZnFe3+2O4. As with another spinel member magnetite, both ferrous (2+) and ferric (3+) iron may be present in Franklinite samples. Di ...

( (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 phosphors. Doped with manganese-II, it fluoresces with a broad white emission band. Some versions had some of the zinc replaced with

beryllium Beryllium is a chemical element with the symbol Be and atomic number 4. It is a steel-gray, strong, lightweight and brittle alkaline earth metal. It is a divalent element that occurs naturally only in combination with other elements to form m ...

. In the 1940s it was largely replaced by the second-generation halophosphors based on the fluorapatite structure. These, in turn have been replaced by the third-generation TriPhosphors. Willemite in natural and ultraviolet light

Willemite in natural and ultraviolet light

References

External links

*{{Commons category-inline Nesosilicates Zinc minerals Trigonal minerals Minerals in space group 148 Luminescent minerals Minerals described in 1829

Occurrence

Uses

See also

References

External links