carrollite

{{Infobox mineral | name = Carrollite | category = Sulfide mineral Thiospinel group (Spinel structural group) | boxwidth = 24 | image = Carrollite02.jpg | imagesize = 260px | caption = Carrollite from Kambove, Katanga. This specimen is 4.3 cm wide, with a 1.2 cm carrollite crystal partly covered by pyrite, between calcite crystals. | formula = CuCo2S4 | IMAsymbol=Cli | molweight = | strunz = 2.DA.05 | dana = 2.10.1.2 | system = Isometric | class = Hexoctahedral (mm) H-M symbol: (4/m 2/m) | symmetry = Fdm | color = Light to dark gray, rarely tarnishes to copper red or violet gray | habit = Octahedral and cubic crystals, also massive, granular or compact | lattice = | twinning = {111} Polysynthetic or spinel twins | cleavage = Imperfect on {001} | fracture = Conchoidal, subconchoidal or uneven | tenacity = Very brittle | mohs = 4.5 to 5.5 | luster = Metallic | refractive = n is not determined for an opaque mineral | opticalprop = | birefringence = | pleochroism = | streak = Grey black | gravity = 4.5 to 4.8 measured, 4.83 calculated | density = | melt = | fusibility = | diagnostic = | solubility = Minerals of the linneite group are partly etched by nitric acid, with slight effervescence. | diaphaneity = Opaque. R is 43% to 45% for lambda = 560 nm | other = Not radioactive, not fluorescent | references = }}

Carrollite, CuCo2S4, is a sulfide of copper and cobalt, often with substantial substitution of nickel for the metal ions, and a member of the linnaeite group. It is named after the type locality in Carroll County, Maryland, US, at the Patapsco mine, Sykesville.