sphalerite

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Related to Black-jack ore: wurtzite, Marmatite

sphalerite

(sfăl`ərīt, sfā`–), mineral composed of zinc sulfide, usually containing some iron and a little cadmium. It occurs in crystals of the isometric system but more generally in cleavable, compact masses. It is transparent to translucent and varies greatly in color, iron-free specimens being pale yellow and those with iron being brown, red, black, or green. The most important source of zinczinc,
metallic chemical element; symbol Zn; at. no. 30; at. wt. 65.38; m.p. 419.58°C;; b.p. 907°C;; sp. gr. 7.133 at 25°C;; valence +2. Zinc is a lustrous bluish-white metal. It is found in Group 12 of the periodic table.
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, sphalerite is a widely distributed mineral that commonly occurs in association with galena. It is found in large deposits in many parts of the world.

Sphalerite

 

(also blende), a mineral of the sulfide class with the chemical composition ZnS (67.1 percent Zn and 32.9 percent S). Sphalerite contains isomorphous admixtures of Fe (up to 26 percent), Mn, Cd, Ga, Ge, In, Co, and Hg. Varieties rich in Fe are known as marmatite, while the colorless and nearly colorless varieties are known as cleiophane. The structure of sphalerite is one of very dense cubic packing of S atoms with the tetrahedral interstices occupied by Zn atoms. The hexagonal modification of ZnS is called wurtzite. Certain sphalerites occur as banded inter-growths of cubic and hexagonal polytypic varieties.

Sphalerite occurs as granular masses, and the mineral frequently forms tetrahedral or dodecahedral crystals. In the absence of admixtures, it is colorless. The variations in color between brown and black are explained by the content of Fe. If Fe is present in small quantities, the greenish yellow color is caused by Cd, and the red color by Mn, Cu, and Ag and by In and Tl. Sphalerite has an adamantine luster, a hardness on Mohs’ scale of 3.5–1.0, and a density of 3,900–4,100 kg/m3, and it possesses piezoelectric and pyroelectric properties. It is formed in hydrothermal deposits together with galena, pyrite, chalcopyrite, arseno-pyrite, quartz, calcite, barite, and dolomite and in sedimentary deposits. In the zone of oxidation, sphalerite alters to zinc sulfate (goslarite) and smithsonite. Sphalerite is an important zinc ore.

A. S. MARFUNIN

sphalerite

[′sfal·ə‚rīt]
(mineralogy)
(Zn,Fe)S The low-temperature form and common polymorph of zinc sulfide; a usually brown or black mineral that crystallizes in the hextetrahedral class of the isometric system, occurs most commonly in coarse to fine, granular, cleanable masses, has resinous luster, hardness of 3.5 on Mohs scale, and specific gravity of 4.1. Also known as blende; false galena; jack; lead marcasite; mock lead; mock ore; pseudogalena; steel jack.