Sphalerite

Sphalerite-unit-cell-depth-fade-3D-balls

Sphalerite fluorescing

Etoile d'Asturies, sphalerite

Sphalerite-barite (Cumberland Mine, Smith County, Tennessee, USA)

Sphalerite on dolostone (Millersville Quarry, Sandusky County, Ohio, USA)

Calcite-Sphalerite-elm05b

Sphalerite is a mineral that serves as the chief ore of zinc. It consists largely of zinc sulfide in crystalline form but almost always contains variable iron. When iron content is high, sphalerite is an opaque black variety called marmatite. It is usually found in association with galena, pyrite, and other sulfides along with calcite, dolomite, and fluorite. Miners have also been known to refer to sphalerite as zinc blende, black-jack, and ruby zinc.

Properties

Sphalerite has a chemical formula of (Zn,Fe)S. It crystallizes in the cubic crystal system and has a tetrahedral crystal structure. The mineral has a hardness of 3.5-4 on the Mohs scale of mineral hardness and a specific gravity of about 3.9 to 4.1, which is high for a non-metallic mineral. The refractive index of sphalerite can be as high as 2.369, which is unusually high for a mineral and gives it a diamond-like luster. This property is known as dispersion and is particularly noticeable in clear, high-quality crystals, which can display a range of spectral colors.

Occurrence

Sphalerite is found in many parts of the world. Major sphalerite deposits are located in Australia, Canada, the United States, and Central and Eastern Europe. It forms in hydrothermal veins when zinc ions in solution are deposited by hot, acidic volcanic fluids. These hydrothermal veins often contain other valuable metals such as lead, silver, and copper, making sphalerite a key mineral in the mining industry.

Uses

The primary use of sphalerite is in the production of zinc metal. The zinc extracted from sphalerite is used for galvanization to protect steel from corrosion, in the manufacture of brass and bronze, in batteries, and as a pigment in paints and coatings. Zinc is also an essential element for human health, playing a crucial role in enzyme function, protein synthesis, and immune system health.

Environmental and Health Concerns

Mining and processing sphalerite can lead to environmental issues, including water pollution from mine runoff and air pollution from the release of sulfur dioxide during the smelting process. Exposure to high levels of zinc can cause health problems, such as stomach cramps, skin irritations, and vomiting. However, zinc is also a trace element necessary for human health, and deficiency can lead to a variety of health issues.

Gallery

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See Also

• Galena
• Pyrite
• Calcite
• Dolomite
• Fluorite

References

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