Color is white, colorless, yellowish, reddish, gray, brown and green. Luster is vitreous to greasy. Crystals are transparent to translucent. Also in porcelain-like masses that form nodules. Aggregates can be fibrous or granular.
Cleavage is absent.
Fracture is conchoidal to uneven. Associated Minerals are prehnite , danburite , babingtonite , epidote , copper , calcite , quartz and zeolites . Best Field Indicators are crystal habit, absence of cleavage, hardness and color.