covellite

{{Infobox mineral | name = Covellite | category = Sulfide mineral | boxwidth = | boxbgcolor = | image = Covellite-252597.jpg | imagesize = 260px | caption = | formula = CuS (copper monosulfide) | IMAsymbol = Cv | molweight = | strunz = 2.CA.05a | dana = 02.08.12.01 | system = Hexagonal | class = Dihexagonal dipyramidal (6/mmm) H–M Symbol (6/m 2/m 2/m) | symmetry = P63/mmc | unit cell = a = 3.7938 Å, c = 16.341 Å; Z = 6 | color = Indigo-blue or darker, commonly highly iridescent, brass-yellow to deep red | habit = Thin platy hexagonal crystals and rosettes also massive to granular. | twinning = | cleavage = Perfect on {0001} | fracture = | tenacity = Flexible | mohs = 1.5–2 | luster = Submetallic, inclining to resinous to dull | refractive = nω = 1.450 nε = 2.620 | opticalprop = Uniaxial (+) | birefringence = | pleochroism = Marked, deep blue to pale blue | streak = Lead gray | gravity = 4.6–4.8 | melt = | fusibility = 2.5 | diagnostic = | solubility = | diaphaneity = Opaque | other = Micaceous cleavage | references = }}

thumb|Covellite (gray) replacing and embaying chalcopyrite (light), polished section from Horn Silver Mine, San Francisco Mining District, Utah. Enlarged to 210 diameters. |alt= Covellite (also known as covelline) is a rare copper sulfide mineral with the formula CuS. 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.