Fletcherite

Fletcherite is a rare thiospinel sulfide mineral with formula Cu(Ni,Co)₂S₄. It is an opaque metallic steel gray mineral which crystallizes in the cubic crystal system. It is a member of the linnaeite group.

This article is about the mineral. For the followers of fletcherism, see Horace Fletcher.

Fletcherite
General
Category	Sulfide mineral Thiospinel group Spinel structural group
Formula (repeating unit)	Cu(Ni,Co)2S4
Strunz classification	2.DA.05
Crystal system	Cubic
Crystal class	Hexoctahedral (m3m) H–M Symbol: (4/m 3 2/m)
Space group	Fd3m
Unit cell	a = 9.520 Å; Z = 8
Identification
Color	Steel gray, creamy white in polished section
Crystal habit	Minute subhedral to euhedral crystals typically enclosed within other sulfide minerals
Mohs scale hardness	5
Luster	Metallic
Diaphaneity	Opaque
Specific gravity	4.76 calculated
Polish luster	Good polish with moderate reflectivity
Optical properties	Isotropic
References	[1][2][3][4]

It was first described in 1977 for an occurrence in the Fletcher Mine, Viburnum Trend (New Lead Belt), near Centerville, Reynolds County, Missouri.[2][1]

It occurs as a dissemination within copper sulfide minerals in mineralization replacing dolomite at the type locality in the Fletcher mine where it is associated with vaesite, pyrite, covellite, chalcopyrite, bornite and digenite. In an occurrence in Kalgoorlie, Australia it is found in black slate associated with pyrrhotite.[1]

References

1. Handbook of Mineralogy
2. Mindat
3. Webmineral data
4. Craig, J. R.; Carpenter, A. B. (1 May 1977). "Fletcherite, Cu(Ni,Co)₂S₄, a new thiospinel from the Viburnum Trend (New Lead Belt), Missouri". Economic Geology. 72 (3): 480–486. doi:10.2113/gsecongeo.72.3.480.