Bixbyite is a manganese oxide mineral : (Mn,Fe)2O3. 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.
It is commonly associated with beryl , spessartine, hausmannite in pneumatolytic or hydrothermal veins and cavities and in metamorphic rocks cavities in rhyolite Typical localities are Jhabua districts, India in Juab County, Utah. It is also reported from San Luis Potosi, Argentina , Spain, Zimbabwe
Bixbyite was named for the American mineralogist Maynard Bixby (1853–1935), responsible for its discovery in 1897. It should not be confused with bixbite, a red form of beryl; to avoid confusion, this name has been deprecated from the CIBJO and the IMA.