bixbyite

{{Infobox mineral | name = Bixbyite | image = Bixbyite-160214.jpg | imagesize = 260px | alt = | caption = | category = Oxide minerals | formula = | IMAsymbol=Bxb | molweight = 158.33 g/mol | strunz = 4.CB.10 | dana = 4.3.7.2 | system = Cubic | class = Diploidal (m) H-M symbol: (2/m ) | symmetry = Ia | unit cell = a = 9.411 Å; Z = 16 | colour = | color = Black | habit = Massive to crystalline | twinning = On {111}, as penetration twins | cleavage = Imperfect on {111}, in traces | fracture = Irregular to uneven | tenacity = | mohs = 6 – | luster = Metallic | streak = Black | diaphaneity = Opaque | gravity = 5.12 | density = 4.95 | polish = | opticalprop = Isotropic | refractive =2.51 – 2.56 | birefringence = | pleochroism = | 2V = | dispersion = | extinction = | length fast/slow = | fluorescence = | absorption = | melt = | fusibility = | diagnostic = | solubility = | impurities = Al, Mg, Si, Ti | alteration = | other = | prop1 = | prop1text = | references = }}

Bixbyite is a manganese iron oxide mineral with chemical formula: . The iron/manganese ratio is quite variable and many specimens have almost no iron. It is a metallic dark black with a Mohs hardness of 6.0 – 6.5. It is a somewhat rare mineral sought after by collectors as it typically forms euhedral isometric crystals exhibiting various cubes, octahedra, and dodecahedra.