| Greenockite | |
|---|---|
Greenockite crystals from Tsumeb Mine, Namibia (Picture width 1 mm) |
|
| General | |
| Category | mineral |
| Chemical formula | CdS |
| Strunz classification | 02.CB.45 |
| Identification | |
| Molar mass | 144.48 |
| Color | Honey yellow, Citron yellow, Orange yellow. |
| Crystal habit | Colloform - Forming from a gel or colloidal mass; Encrustations - Forms crust-like aggregates on matrix; Radial - Crystals radiate from a center without producing stellar forms (e.g. stibnite) |
| Crystal system | Hexagonal (6mm) Space Group: P 63mc |
| Cleavage | [1120] Distinct, [0001] Imperfect |
| Fracture | Uneven - Flat surfaces (not cleavage) fractured in an uneven pattern. |
| Mohs scale hardness | 3.5-4 |
| Luster | Adamantine - Resinous |
| Streak | orange yellow |
| Specific gravity | 3.98 - 5, Average = 4.49 |
| Optical properties | Uniaxial, a=2.506, b=2.529, bire=0.0230 |
| Other characteristics | Nonmagnetic, non-radioactive |
Greenockite is a rare cadmium mineral that consists of cadmium sulfide, CdS, in crystalline form. Greenockite crystallizes in the hexagonal system. It occurs as massive encrustations and as six-sided pyramidal crystals which vary in color from a honey yellow through shades of red to brown. The Mohs hardness is 3 to 3.5 and the specific gravity is 4.5 to 5.
Greenockite occurs with other sulfide minerals such as sphalerite and galena. It is the only ore mineral of cadmium, most cadmium is recovered as a byproduct of zinc and lead mining.
It was first recognized in 1840 in Bishopton, Scotland, during the cutting of a tunnel for the Glasgow, Paisley and Greenock Railway. The mineral was named after the land owner Lord Greenock. It is also known from the lead-zinc districts of the central United States.