Luster is vitreous. Crystals are transparent to translucent. The crystals are typically pseudo-octahedrons, some of which are twinned in a special twin called the spinel twin . The more commonly observed habit is radiating clusters and spherical aggregates. Cleavage is absent.
Fracture is conchoidal.
Streak is clear. Refractive index is approximately 1.48 Associated Minerals include tridymite , sanadine , hornblende , beta quartz , olivine , pseudobrookite and augite .