Color is commonly yellow, but also brown, reddish brown and red. Luster is bright vitreous to resinous. Crystals are translucent with some unusual specimens being transparent. Good crystals show multiple facets without discernible symmetry. Also found massive.
Fracture is subconchoidal.
Twinning may be seen as lamellar striations and some specimens display yellow fluorescence. Best Field Indicators are crystal habit, color, luster, cleavage, environment of formation and hardness.