Mineral Information and Data:

CdS [CNMNC approved formula]

Named in honor of Charles Murray Cathcart (1783–1859), Lord Greenock.

IMA status : Valid species (Pre-IMA 1840) Grandfathered
(8th edition) :  
  (02) Sulfides - Including Selenides and Tellurides
  (02.08) where Am Bn Xp, with (m+n):p=1:1
  (02.08.07) Wurtzite Group (Hexagonal: P63mc)
(10th edition) :
  (02) Sulfides
  (02.C) Metal Sulfides, M:S = 1:1 (and similar)
  (02.CB) With Zn, Fe, Cu, Ag, etc.
Crystal system: Hexagonal System
Point group (H-M): 6mm — dihexagonal-pyramidal
Space group: P63mc
Unit cell: a = 4.136Å, c = 6.713Å, Z=2
Crystal Habit: Crystals hemimorphic pyramidal, to 3 cm; most commonly as earthy coatings.
Twinning: Twin plane {1122} rare, forming fourlings
Color: Shades of yellow and orange, rarely deep red; in polished section, very pale lemon-yellow to red-brown and blood-red
Diaphaneity: Nearly opaque to translucent
Luster: Adamantine to resinous
Hardness (Mohs): 3 - 3.5
Measured Density: 4.820 g/cm3
Cleavage: Distinct on {1122}, imperfect on {0001}
Tenacity: Brittle
Fracture: Conchoidal
Streak: Yellow-orange to brick-red
Polymorphism and Series: Dimorphous with hawleyite.
Geologic Setting: As earthy coatings, especially on sphalerite, in which it also occurs as a substituent; also rarely as crystals in cavities in mafic igneous rocks; in high-temerature hydrothermal vein deposits.
Mineral Association: Sphalerite, smithsonite, prehnite, other zeolites (low temperature); cassiterite, tetrahedrite, herzenbergite, chalcopyrite, other sulfides (high temperature)
Other Properties: Gemstone Unlikely Available.


Greenockite on prehnite
Origin: Summit, Union Co., New Jersey, U.S.A.
Sample size: Microscopic image
Photo and Owner: Lou Perloff


Bright yellow-orange crust on sphalerite matrix and included in tiny 1 mm hemimorphite crystals spread across the surface.
Origin: New Glencrieff mine, Wanlockhead, Dumfriesshare, Scotland
Sample size: 4.5 x 3.5 x 1 cm
Photo: Tom Loomis


(zoom-in of above)