| Tennantite | |
|---|---|
A sample of tennantite |
|
| General | |
| Category | Sulfosalt minerals |
| Chemical formula | Cu12As4S13 |
| Strunz classification | 02.GB.05 |
| Identification | |
| Molar mass | 1,471.40 gm |
| Color | Flint-gray to iron-black, cherry-red in transmitted light |
| Crystal habit | massive to well formed crystals |
| Crystal system | Cubic Hextetrahedral H-M Symbol (43m) Space Group: I 43m |
| Twinning | Contact and penetration twins |
| Cleavage | None |
| Fracture | Subconchoidal to uneven |
| Tenacity | Somewhat brittle |
| Mohs scale hardness | 3 - 4.5 |
| Luster | Metallic, commonly splendent |
| Streak | reddish gray |
| Diaphaneity | Opaque, except in very thin fragments |
| Specific gravity | 4.65 |
| Polish luster | gray, inclining to black to brown to cherry-red |
| Optical properties | Isotropic |
| Refractive index | n greater than 2.72 |
| References | [1][2][3] |
Tennantite is a copper arsenic sulfosalt mineral. Its chemical formula is Cu12As4S13. It is grey-black, steel-gray, iron-gray or black in color. A closely related mineral, tetrahedrite (Cu12Sb4S13) has antimony substituting for arsenic and the two form a solid solution series. The two have very similar properties and is often difficult to distinguish between tennantite and tetrahedrite. Iron, zinc, and silver substitute up to about 15% for the copper site.[2][1]
The mineral was first described for an occurrence in Cornwall, England in 1819 and named after the English chemist Smithson Tennant (1761-1815).[2]
It is found in hydrothermal veins and contact metamorphic deposits in association with other Cu–Pb–Zn–Ag sulfides and sulfosalts, pyrite, calcite, dolomite, siderite, barite, fluorite and quartz.[1]