Color is most commonly white, colorless, greenish or gray but also yellow, brown, reddish, pink, violet or blue colors are possible. Luster is vitreous on freshly exposed crystals or surfaces but weathering causes a dulling of the luster. Crystals are translucent to transparent. Complete crystals are rare and often the crystals will have distorted shapes with uneven faces. Cleavage is distinct in several prismatic directions producing a splintery almost fibrous appearance in cleaved massive specimens.
Fracture is subconchoidal to uneven.
Streak is white. Associated Minerals include hornblende , the garnet minerals almandine and andradite , actinolite , microcline , pyroxenes , apatite , andalusite , zircon , sphene , diopside and muscovite . Best Field Indicators include color, crystal habit, cleavage surface features, fluorescence and hardness.