Sphalerite
Sphalerite (sometimes spelled sphaelerite) is a sulfide mineral with the chemical formula (Zn,Fe)S. 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.
| Sphalerite | |
|---|---|
Black crystals of sphalerite with minor chalcopyrite and calcite | |
| General | |
| Category | Sulfide mineral |
| Formula (repeating unit) | (Zn,Fe)S |
| IMA symbol | Sp |
| Strunz classification | 2.CB.05a |
| Dana classification | 02.08.02.01 |
| Crystal system | Cubic |
| Crystal class | Hextetrahedral (43m) H-M symbol: (4 3m) |
| Space group | F43m (No. 216) |
| Unit cell | a = 5.406 Å; Z = 4 |
| Structure | |
| Jmol (3D) | Interactive image |
| Identification | |
| Color | Light to dark brown, red-brown, yellow, red, green, light blue, black and colourless. |
| Crystal habit | Euhedral crystals – occurs as well-formed crystals showing good external form. Granular – generally occurs as anhedral to subhedral crystals in matrix. |
| Twinning | Simple contact twins or complex lamellar forms, twin axis [111] |
| Cleavage | perfect dodecahedral on [011] |
| Fracture | Uneven to conchoidal |
| Mohs scale hardness | 3.5–4 |
| Luster | Adamantine, resinous, greasy |
| Streak | brownish white, pale yellow |
| Diaphaneity | Transparent to translucent, opaque when iron-rich |
| Specific gravity | 3.9–4.2 |
| Optical properties | Isotropic |
| Refractive index | nα = 2.369 |
| Other characteristics | non-radioactive, non-magnetic, fluorescent and triboluminescent. |
| References | |
German geologist Ernst Friedrich Glocker discovered sphalerite in 1847, naming it based on the Greek word sphaleros, 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.