It can be found in pegmatite dikes up to 20cm and as black prisms in marble xenoliths. Fresh crystals are black and display a vitreous to dull luster, while in altered pegmatites the crystals may be partially altered or etched. Magnesio -arfvedsonite is also found at MSH, it is indistinguishable without chemical analysis.
Color is dark green to gray, black.
Luster is vitreous to dull. Diaphaneity is opaque. Crystal Habits include excellent prismatic crystals, prisms and pitted somewhat fibrous crystals. Fracture is uneven to subconchoidal. Hardness is 5 to 6.