Luster is vitreous. Crystals are transparent to translucent. Aggregates form crusts and granular masses. Twinning is common with the penetration twin rotated around the c-axis. Cleavage is poor in three directions parallel to the faces of the rhombohedron.
Fracture is uneven.
Hardness is 4 - 5. Streak is white. Unlike calcite, does not react to acids. Associated Minerals are quartz , calcite , scolecite , apophyllite , natrolite , heulandite , stilbite and other zeolites . Best Field Indicators are crystal habit and symmetry, density, hardness, luster, lack of reaction to acids and associations.