The two octahedron faces parallel to the twin plane are equilateral triangles. Each point of the triangles is doubled across the twin plane with an indentation between them. The crystal looks like it has trigonal symmetry, but the three indentations are a clue that this crystal is a twin. Twins of spinel are rare, but their popularity makes them readily available on the market. Luster is vitreous.
Crystals are transparent to translucent and sometimes nearly opaque.
Also as rounded grains in alluvial placer deposits. None Fracture is conchoidal. Associated Minerals include calcite , dolomite , corundum and garnets . Notable Occurrences include Burma, Sri Lanka, Brazil and Afghanistan. Best Field Indicators are twinned crystals if present, color, hardness, density and locality.