Greenockite
General
Category	mineral
Chemical formula	CdS
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.

[edit] References

• Mindat
• Webmineral
• Mineral galleries
• Glasgow museum site

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