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, Mississippi-Valley type, and volcanogenic massive sulfide deposits. It is found in association with galena, chalcopyrite, pyrite (and other sulfides), calcite, dolomite, quartz, rhodochrosite, and fluorite.

German geologist Ernst Friedrich Glocker discovered sphalerite in 1847, naming it based on the Greek word (), meaning 'deceiving', due to the difficulty of identifying the mineral.

In addition to zinc, sphalerite is an ore of cadmium, gallium, germanium, and indium. Miners have been known to refer to sphalerite as zinc blende, black-jack, and ruby blende. Marmatite is an opaque black variety with a high iron content.

Crystal habit and structure

left|thumb|The crystal structure of sphalerite

Sphalerite crystallizes in the face-centered cubic zincblende crystal structure, which was named after the mineral. This structure is a member of the hextetrahedral crystal class (space group F3m). In the crystal structure, both the sulfur and the zinc or iron ions occupy the points of a face-centered cubic lattice, with the two lattices displaced from each other such that the zinc and iron are tetrahedrally coordinated to the sulfur ions, and vice versa. Minerals similar to sphalerite include those in the sphalerite group, consisting of sphalerite, colaradoite, hawleyite, metacinnabar, stilleite and tiemannite. The structure is closely related to the structure of diamond. The lattice constant for zinc sulfide in the zinc blende crystal structure is 0.541 nm. Sphalerite has been found as a pseudomorph, taking the crystal structure of galena, tetrahedrite, barite and calcite. Sphalerite can have Spinel Law twins, where the twin axis is [111].

The chemical formula of sphalerite is ; the iron content generally increases with increasing formation temperature and can reach up to 40%. Cadmium can replace up to 1% of zinc and manganese is generally found in sphalerite with high iron abundances. In pure form, it is a semiconductor, but transitions to a conductor as the iron content increases. It has a hardness of 3.5 to 4 on the Mohs scale of mineral hardness. In thin section, sphalerite exhibits very high positive relief and appears colorless to pale yellow or brown, with no pleochroism. Sphalerite has a characteristic triboluminescence of yellow-orange. Typically, specimens cut into end-slabs are ideal for displaying this property. An identification method based on a mineral's optical properties and powered by artificial intelligence algorithms showed good results.

Varieties

Gemmy, colorless to pale green sphalerite from Franklin, New Jersey (see Franklin Furnace), are highly fluorescent orange and/or blue under longwave ultraviolet light and are known as cleiophane, an almost pure ZnS variety. Cleiophane contains less than 0.1% of iron in the sphalerite crystal structure. Red, orange or brownish-red sphalerite is termed ruby blende or ruby zinc, whereas dark colored sphalerite is termed black-jack. hydrothermal deposits, sedimentary beds, volcanogenic massive sulfide deposits (VMS), Mississippi-valley type deposits (MVT), granite

Sedimentary exhalitive

Approximately 50% of zinc (from sphalerite) and lead comes from Sedimentary exhalative (SEDEX) deposits, which are stratiform Pb-Zn sulfides that form at seafloor vents. The metals precipitate from hydrothermal fluids and are hosted by shales, carbonates and organic-rich siltstones in back-arc basins and failed continental rifts. The main ore minerals in SEDEX deposits are sphalerite, galena, pyrite, pyrrhotite and marcasite, with minor sulfosalts such as tetrahedrite-freibergite and boulangerite; the zinc + lead grade typically ranges between 10 and 20%.

Mississippi-Valley type

Similar to SEDEX, Mississippi-Valley type (MVT) deposits are also a Pb-Zn deposit which contains sphalerite. However, they only account for 15–20% of zinc and lead, are 25% smaller in tonnage than SEDEX deposits and have lower grades of 5–10% Pb + Zn. The ore minerals are the same as SEDEX deposits: sphalerite, galena, pyrite, pyrrhotite and marcasite, with minor sulfosalts.

Volcanogenic massive sulfide

Volcanogenic massive sulfide (VMS) deposits can be Cu-Zn- or Zn-Pb-Cu-rich, and accounts for 25% of Zn in reserves. The most abundant ore minerals are pyrite, chalcopyrite, sphalerite and pyrrhotite.

Localities

The top producers of sphalerite include the United States, Russia, Mexico, Germany, Australia, Canada, China, Ireland, Peru, Kazakhstan and England.

Sources of high quality crystals include:

{|class="wikitable"

!Place!!Country

|-

|Freiberg, Saxony, <br>Neudorf, Harz Mountains||Germany

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|Lengenbach Quarry, Binntal, Valais|| Switzerland

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| Horní Slavkov and Příbram||Czech Republic

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|Rodna|| Romania

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|Madan, Smolyan Province, Rhodope Mountains|| Bulgaria

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| Aliva mine, Picos de Europa Mountains, Cantabria [Santander] Province|| Spain

|-

| Alston Moor, Cumbria|| England

|-

|Dalnegorsk, Primorskiy Kray|| Russia

|-

|Watson Lake, Yukon Territory|| Canada

|-

|Flin Flon, Manitoba||Canada

|-

|Tri-State district including deposits near<br>Baxter Springs, Cherokee County, Kansas;<br>Joplin, Jasper County, Missouri<br>and Picher, Ottawa County, Oklahoma||US

|-

|Elmwood mine, near Carthage, Smith County, Tennessee||US

|-

|Eagle mine, Gilman district, Eagle County, Colorado||US

|-

|Santa Eulalia, Chihuahua||Mexico

|-

|Naica, Chihuahua||Mexico

|-

|Cananea, Sonora||Mexico

|-

|Huaron||Peru

|-

|Casapalca||Peru

|-

|Huancavelica||Peru

|-

|Zinkgruvan|| Sweden

|}

Uses

Metal ore

Sphalerite is an important ore of zinc; around 95% of all primary zinc is extracted from sphalerite ore. However, due to its variable trace element content, sphalerite is also an important source of several other metals such as cadmium, gallium, germanium, and indium which replace zinc. The ore was originally called blende by miners (from German blind or deceiving) because it resembles galena but yields no lead.

Brass and bronze

The zinc in sphalerite is used to produce brass, an alloy of copper with 3–45% zinc. Sphalerite may have also been used during the cementation process of brass in Northern China during the 12th–13th century CE (Jin Dynasty). Besides brass, the zinc in sphalerite can also be used to produce certain types of bronze; bronze is dominantly copper which is alloyed with other metals such as tin, zinc, lead, nickel, iron and arsenic.

thumb|250x250px|Faceted sphalerite, known by the name of Étoile des Asturies, one of the largest in existence. It actually comes from the Aliva mine, Cantabria (Spain). Cantonal Museum of Geology of Lausanne.

Other

  • Yule Marble – sphalerite is found as inclusions in yule marble, which is used as a building material for the Lincoln Memorial and Tomb of the Unknown.
  • Galvanized iron – zinc from sphalerite is used as a protective coating to prevent corrosion and rusting; it is used on power transmission towers, nails and automobiles.
  • Gemstone. - Sphalerite has a high refractive index, close to that of diamond, and an even greater dispersion. The yellowish-green or intense orange color of the variety known as ruby blende allows for the cutting of very beautiful collector’s gems. The problems preventing its use in jewelry are its low hardness (3.5–4 on the Mohs scale) and its fragility, due to its perfect cleavage. This cleavage, with six distinct planes, also makes it difficult to facet. Gem-quality sphalerite has been extracted mainly from the Áliva mine, in the Picos de Europa (Spain), although it has also occasionally been found in other localities.

<gallery widths="165px" heights="140px">

File:Sphalerite-barite (Cumberland Mine, Smith County, Tennessee, USA).jpg|Sphalerite and barite from Cumberland Mine, Tennessee, US

File:Sphalerite on dolostone (Millersville Quarry, Sandusky County, Ohio, USA).jpg|Sphalerite on dolostone, from Millersville Quarry, Ohio, US

File:Calcite-Sphalerite-elm05b.jpg|Tan crystal of calcite attached to a cluster of black sphalerite crystals

File:Sphalerite-221270.jpg|Sharp, tetrahedral sphalerite crystals with minor associated chalcopyrite from the Idarado Mine, Telluride, Ouray District, Colorado, US

File:Sphalerite-Quartz-261762.jpg|Gem quality twinned cherry-red sphalerite crystal (1.8&nbsp;cm) from Hunan Province, China

File:Esfalerita (Blenda acaramelada) Áliva, Cantabria.jpg|Sphalerite crystals from Áliva, Camaleño, Cantabria (Spain)

File:Fluorite and sphalerite J1.jpg|Purple fluorite and sphalerite, from the Elmwood mine, Smith county, Tennessee, US

File:Geodized brachiopod.jpg|Sphalerite crystal in geodized brachiopod

</gallery>

See also

  • List of minerals

References

Further reading

  • Dana's Manual of Mineralogy
  • Webster, R., Read, P. G. (Ed.) (2000). Gems: Their sources, descriptions and identification (5th ed.), p.&nbsp;386. Butterworth-Heinemann, Great Britain.
  • The sphalerite structure
  • Possible relation of Sphalerite to origins of life and precursor chemicals in 'Primordial Soup'
  • Minerals.net
  • Minerals of Franklin, NJ