It forms in nodules and as crusts in altered granite pegmatites. Crystals tend to be prismatic and are often aggregated together into bundles. Color is brown to white or colorless. Luster is vitreous. Crystals tend to be prismatic and are often aggregated together into bundles.
Cleavage is perfect in one direction.
Fracture is uneven. Hardness is 3.5. Streak is off white. Tip Top Mine, Custer Co., South Dakota, USA, Francois Lake, British Columbia, Canada and at other localities.