Biotite, P. Tarasoff sp. Photo by Violet Anderson Royal Ontario Museum Biotite, one of the several members of the mica group found at MSH is fairly abundant in many environments and as a rock-forming mineral. It is difficult to distinguish from annite.
Color is usually dark red brown to black.
Luster is vitreous to submetallic. Diaphaneity is transparent to opaque. Crystal Habits include short to long pseudohexagonal prisms to several centimeters across. Fracture is not apparent due to cleavage. Hardness is 2.5 - 3.