Luster is greasy to dull, but pearly on cleavage surfaces. Crystals are mostly translucent to opaque. Crystal Habits include the typical fine grained, fibrous and lamellar masses, stellate aggregates and radiating spherules. Individual crystals are rare, but usually have a tabular subhedral or distorted form. Cleavage is perfect in one direction.
Fracture is uneven or splintery.
Streak is white. Cleavage sheets are flexible, but inelastic. A distinctive greasy feel to the touch. Best Field Indicators are crystal habit, color, cleavage, softness, aluminum test and feel.