digenite

{{Infobox mineral | name = Digenite | category = Sulfide mineral | boxwidth = 24 | boxbgcolor = | image = Digenite.jpg | imagesize = 260px | caption = Digenite from the East Colusa Mine, Butte, Montana, US. Specimen size = 4.3 cm | formula = Cu9S5 | IMAsymbol = Dg | molweight = 146.45 g/mol | strunz = 2.BA.05e | dana = 02.04.07.03 | system = Trigonal | class = Hexagonal scalenohedral (m) H-M symbol: ( 2/m) | symmetry = Rm | color = Blue to black | habit = Pseudocubic crystals are rare, usually as intergrowths with other copper sulfides | lattice = | twinning = | cleavage = {111} (observed in synthetic material) | fracture = Conchoidal | tenacity = Brittle | mohs = 2.5 to 3 | luster = Submetallic to metallic | refractive = | opticalprop = Reflectivity: 21.6 at 540 nm | birefringence = | pleochroism = | streak = Black | gravity = 5.5 to 5.7 observed, 5.628 calculated | density = | melt = | fusibility = | diagnostic = | solubility = | diaphaneity = Opaque | other = Distinctly blue in polished sections | references = }}

Digenite is a copper sulfide mineral with formula: Cu9S5. Digenite is a black to dark blue opaque mineral that crystallizes with a trigonal–hexagonal scalenohedral structure. In habit it is usually massive, but does often show pseudo-cubic forms. It has poor to indistinct cleavage and a brittle fracture. It has a Mohs hardness of 2.5 to 3 and a specific gravity of 5.6. It is found in copper sulfide deposits of both primary and supergene occurrences. It is typically associated with and often intergrown with chalcocite, covellite, djurleite, bornite, chalcopyrite and pyrite. The type locality is Sangerhausen, Thuringia, Germany, in copper slate deposits.