Jacobsite
Chemical Formula	MnFe2O4
Species	Oxides & Hydroxides
Crystal System	Isometric
Mohs Scale	5-6
Specific Gravity	5.03
Color	Black to brownish black
Streak	reddish black to brown
Luster	Sub-Metallic
Refractive Index	~?2.3
Diaphaneity	Opaque
Cleavage	, probably a parting
Fracture	Conchoidal
Crystal Habit：Disseminated to massive, rarely as octahedral crystals