Pyrophanite
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Pyrophanite is a manganese titanium oxide mineral with formula: MnTiO₃. It is a member of the ilmenite group. It is a deep red to greenish black mineral which crystallizes in the trigonal system. Wikipedia
Color: Deep blood-red to greenish black
Optical properties: Uniaxial (-)
Refractive index: nω = 2.481 nε = 2.210
Space group: R3