Covellite

Covellite
General
Category	Sulfide mineral
Formula (repeating unit)	CuS (copper monosulfide)
IMA symbol	Cv[1]
Strunz classification	2.CA.05a
Dana classification	02.08.12.01
Crystal system	Hexagonal
Crystal class	Dihexagonal dipyramidal (6/mmm) H–M Symbol (6/m 2/m 2/m)
Space group	P63/mmc
Unit cell	a = 3.7938 Å, c = 16.341 Å; Z = 6
Identification
Color	Indigo-blue or darker, commonly highly iridescent, brass-yellow to deep red
Crystal habit	Thin platy hexagonal crystals and rosettes also massive to granular.
Cleavage	Perfect on {0001}
Tenacity	Flexible
Mohs scale hardness	1.5–2
Luster	Submetallic, inclining to resinous to dull
Streak	Lead gray
Diaphaneity	Opaque
Specific gravity	4.6–4.8
Optical properties	Uniaxial (+)
Refractive index	nω = 1.450 nε = 2.620
Pleochroism	Marked, deep blue to pale blue
Fusibility	2.5
Other characteristics	Micaceous cleavage
References	[2][3][4]

Covellite (also known as covelline) is a rare copper sulfide mineral with the formula CuS.^[4] This indigo blue mineral is commonly a secondary mineral in limited abundance and although it is not an important ore of copper itself, it is well known to mineral collectors.^[4]

The mineral is generally found in zones of secondary enrichment (supergene) of copper sulfide deposits. Commonly found as coatings on chalcocite, chalcopyrite, bornite, enargite, pyrite, and other sulfides, it often occurs as pseudomorphic replacements of other minerals.^[5] The first records are from Mount Vesuvius, formally named in 1832 after N. Covelli.^[4]