Greenockite from Arkansas, USA. (public display, Carnegie Museum of Natural History, Pittsburgh, Pennsylvania, USA) A mineral is a naturally-occurring, solid, i — Photo: James St. John · CC BY 2.0
Greenockite
Cadmium sulfide — a rare hexagonal yellow mineral once called cadmium blende.
Intro adapted from Wikipedia (CC BY-SA).
Greenockite is an IMA-recognized mineral species in the sulfide class, with the chemical formula CdS.
It crystallizes in the hexagonal crystal system (space group P6_3mc). It is a member of the Wurtzite structural group.
Key properties: Mohs hardness 3–3.5; specific gravity 4.82; typically yellow or orange; Yellow-orange to brick-red streak; Adamantine to resinous luster; optically uniaxial.
IMA symbol Gnk, grandfathered status — known before the IMA’s founding, named in 1840.
Occurs as earthy coatings, especially on sphalerite, in which it is also found as a substituent; also rarely as crystals in cavities in mafic igneous rocks; in high-temerature hydrothermal vein deposits.
It is found associated with Sphalerite, smithsonite, prehnite, other zeolites (low temperature); cassiterite, tetrahedrite, herzenbergite, chalcopyrite, other sulfides (high temperature).
In honor of Charles Murray Cathcart (1783–1859), Lord Greenock.
Collections: Collector Favorites, Rare & Remarkable.