Mineral Information and Data:

Digenite
Cu1.8S [CNMNC approved formula]

Named from Greek digenus = of two origins, because it is related to chalcocite and covellite. First published in 1844. Approved and defined (IMA, 1960).

IMA status : Approved Species 1960 ()
CLASSIFICATION 
Dana
(8th edition) :
02.04.07.03  
  (02) Sulfides - Including Selenides and Tellurides
  (02.04) where Am Bn Xp, with (m+n):p=2:1
  (02.04.07) Chalcocite Group ([Cu]2-x S] formulae)
  
Nickel-Strunz
(10th edition) :
02.BA.05e
  (02) Sulfides
  (02.B) Metal Sulfides, M:S > 1:1 (mainly 2:1)
  (02.BA) With Cu, Ag, Au
  
Crystal system: Trigonal System
Point group (H-M): 3m (or 3 2/m) — hexagonal-scalenohedral
Space group: R3m
Unit cell: a = 3.92Å, c = 48Å, Z=15
Crystal Habit: Rarely in pseudocubic crystals, to 3 cm; more commonly as intergrowths with other copper sulfides. Above 73°C, cubic with space group Fm3m, a = 5.57 A, Z = 4.
  
Color: Blue to black; distinctly blue in polished section
Diaphaneity: Opaque
Hardness (Mohs): 2.5 - 3
Measured Density: 5.546 g/cm3
Cleavage: {111} (synthetic)
Tenacity: Brittle
Fracture: Conchoidal
  
Geologic Setting: In hydrothermal copper deposits of primary and secondary origin. Formed under a wide range of conditions; reported from mafic intrusives, as a volcanic exhalation product, and in pegmatites.
Mineral Association: Chalcocite, djurleite, bornite, chalcopyrite, other copper minerals, pyrite
  
Comments: A recent study showed the existence of a complete solid-solution series between high digenite [cubic, high-temperature digenite] and berzelianite (Pirard & Hatert, 2008).

 

Digenite
Origin: Butte, Silver Bow Co., Montana, U.S.A.
Sample size: Microscopic image
Photo and Owner: Lou Perloff

 

Digenite
Origin: Butte, Montana, United States
Sample size: 5.5 x 4.5 x 4 cm
Photo: Tom Loomis

 

Digenite
(zoom-in of above)

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