Bixbyite
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Bixbyite is a manganese iron oxide mineral with formula: (Fe,Mn)2O3. The iron:manganese ratio is quite variable and many specimens have almost no iron. It is a somewhat rare mineral sought after by collectors as it typically forms euhedral isometric crystals exhibiting various cubes, octahedrons, and dodecahedrons. It is a metallic dark black with a Mohs hardness of 6.0 - 6.5 and a specific gravity of 4.9 - 5.0. It is commonly associated with beryl, quartz, spessartine, hematite, pseudobrookite, hausmannite, braunite and topaz in pneumatolytic or hydrothermal veins and cavities and in metamorphic rocks. Type localities are Siapa and Chhindwara, India and the Thomas Range in Juab County, Utah. It is also reported from San Luis Potosi, Mexico; northern Patagonia, Argentina; Gerona, Spain; Sweden and South Africa. Bixbyite was named for the American mineralogist Maynard Bixby.
