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Sphalerite has been found as a pseudomorph, taking the crystal structure of galena, tetrahedrite, barite and calcite. [13] [15] Sphalerite can have Spinel Law twins, where the twin axis is [111]. The chemical formula of sphalerite is (Zn,Fe)S; the iron content generally increases with increasing formation temperature and can reach up to 40%. [6]
This is the main form of zinc found in nature, where it mainly occurs as the mineral sphalerite. Although this mineral is usually black because of various impurities, the pure material is white, and it is widely used as a pigment.
English: Geologic context: sphalerite crystals atop sucrosic dolostone, Lockport Dolomite, upper Niagaran Series, Wenlockian, upper Middle Silurian Locality: Millersville Quarry, northern side of the town of Millersville, southwestern Sandusky County, northwestern Ohio, USA. Photo taken by James St. John.
Galena is the main ore of lead, used since ancient times, [6] since lead can be smelted from galena in an ordinary wood fire. [7] Galena typically is found in hydrothermal veins in association with sphalerite, marcasite, chalcopyrite, cerussite, anglesite, dolomite, calcite, quartz, barite, and fluorite.
Streak can be used when properties between pyrrhotite and other sulfide minerals are similar. Pyrrhotite displays a dark grey to black streak. [ 15 ] Pyrite will display a greenish black to brownish black streak, [ 16 ] chalcopyrite will display a greenish black streak, [ 17 ] and pentlandite leaves a pale bronze-brown streak. [ 18 ]
At temperatures typically used for smelting metals, zinc is a gas that will escape from a furnace with the flue gas and be lost, unless specific measures are taken to prevent it. The most common zinc concentrate processed is zinc sulfide, [1] which is obtained by concentrating sphalerite using the froth flotation method.
The zinc in sphalerite is also used to produce brass. This sample was extracted in Creede, Colorado , and features black tetrahedral crystals of sphalerite up to 8 mm (0.31 in) in size, with minor chalcopyrite and calcite, in a 4.5 cm × 3.0 cm × 2.0 cm (1.77 in × 1.18 in × 0.79 in) matrix .
Gem-quality material is usually a strong yellow to honey brown, orange, red, or green; its very high RI (2.37) and dispersion (0.156) make for an extremely lustrous and fiery gem, and it is also isotropic. But here again, its low hardness (2.5–4) and perfect dodecahedral cleavage preclude sphalerite's wide use in jewelry.