Willemite is a zinc

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, the crystalline forms of silica (silicon dio ...

() and a minor ore of zinc. It is highly

fluorescent Fluorescence is one of two kinds of photoluminescence, the emission of light by a substance that has absorbed light or other electromagnetic radiation. When exposed to ultraviolet radiation, many substances will glow (fluoresce) with color ...

(green) under shortwave

ultraviolet Ultraviolet radiation, also known as simply UV, is electromagnetic radiation of wavelengths of 10–400 nanometers, shorter than that of visible light, but longer than X-rays. UV radiation is present in sunlight and constitutes about 10% of ...

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; it has Symbol (chemistry), symbol Mn and atomic number 25. It is a hard, brittle, silvery metal, often found in minerals in combination with iron. Manganese was first isolated in the 1770s. It is a transition m ...

, 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" or "old mine", and this is also reflected in its German name, (earlier, ). The mine was once a ...

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; 24 August 1772 – 12 December 1843) was King of the Netherlands and List of monarchs of Luxembourg, Grand Duke of Luxembourg from 1815 until his abdication in 1840. Born as the son of William V, Prince of Orange, ...

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

Gerard Troost Gerardus Troost (March 5, 1776 – August 14, 1850) was a Dutch- American medical doctor, naturalist, mineralogist, and founding member and first president of the Philadelphia Academy of Natural Sciences.; archive.org copie Biography Troost was ...

Occurrence

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

Willemite is usually formed as an alteration of previously existing

sphalerite Sphalerite is a sulfide mineral with the chemical formula . It is the most important ore of zinc. Sphalerite is found in a variety of deposit types, but it is primarily in Sedimentary exhalative deposits, sedimentary exhalative, Carbonate-hoste ...

ore bodies, and is usually associated with

limestone Limestone is a type of carbonate rock, carbonate sedimentary rock which is the main source of the material Lime (material), lime. It is composed mostly of the minerals calcite and aragonite, which are different Polymorphism (materials science) ...

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

hemimorphite Hemimorphite is the chemical compound Zinc, Zn4(Pyrosilicate, Si2O7)(Hydroxide, OH)2Water of crystallization, ·H2O, a component of mineral Calamine (mineral), calamine. It is a silicate mineral which, together with smithsonite (ZnCO3), has bee ...

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 and characters * Franklin (given name), including list of people and characters with the name * Franklin (surname), including list of people and characters with the name * Franklin (class), a member of a historic ...

and

Sterling Hill Mine The Sterling Hill Mine, now known as the Sterling Hill Mining Museum, is a former zinc mine in Ogdensburg, New Jersey, Ogdensburg, Sussex County, New Jersey, Sussex County, New Jersey, United States. It was the last working underground mine in ...

s in

New Jersey New Jersey is a U.S. state, state located in both the Mid-Atlantic States, Mid-Atlantic and Northeastern United States, Northeastern regions of the United States. Located at the geographic hub of the urban area, heavily urbanized Northeas ...

. 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 hexago ...

(zinc oxide) and

franklinite Franklinite is an oxide mineral belonging to the normal spinel subgroup's iron (Fe) series, with the formula Zn2+Fe23+O4. As with another spinel member magnetite, both ferrous (2+) and ferric (3+) iron may be present in franklinite samples. Div ...

( (an iron rich zinc mineral occurring in sharp black

isometric The term ''isometric'' comes from the Greek for "having equal measurement". isometric may mean: * Cubic crystal system, also called isometric crystal system * Isometre, a rhythmic technique in music. * "Isometric (Intro)", a song by Madeon from ...

octahedral crystals and masses). Franklinite and zincite are not fluorescent.

Uses

Artificial willemite was used as the basis of first-generation

fluorescent tube A fluorescent lamp, or fluorescent tube, is a low-pressure mercury-vapor gas-discharge lamp that uses fluorescence to produce visible light. An electric current in the gas excites mercury vapor, to produce ultraviolet and make a phosphor ...

phosphor A phosphor is a substance that exhibits the phenomenon of luminescence; it emits light when exposed to some type of radiant energy. The term is used both for fluorescent or phosphorescent substances which glow on exposure to ultraviolet or ...

s. When doped with manganese ions, it fluoresces with a broad white emission band. Some versions had some of the zinc replaced with

beryllium Beryllium is a chemical element; it has Symbol (chemistry), symbol Be and atomic number 4. It is a steel-gray, hard, strong, lightweight and brittle alkaline earth metal. It is a divalent element that occurs naturally only in combination with ...

. In the 1940s it was largely replaced by second-generation halophosphors based on

fluorapatite Fluorapatite, often with the alternate spelling of fluoroapatite, is a phosphate mineral with the formula Ca5(PO4)3F (calcium fluorophosphate). Fluorapatite is a hard crystalline solid. Although samples can have various color (green, brown, blu ...

. These, in turn have been replaced by the third-generation TriPhosphors. 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