It is the monoclinic dimorph of epididymite. Color is usually colorless to white, rarely pale pink. Luster is vitreous to silky. Diaphaneity is transparent to translucent. Crystal Habits include thin tabular euhedral crystals, the twinned crystals sometimes form attractive stellate groups ressembling the epididymite trillings.
Fracture is uneven.
Hardness is 6 - 7. Streak is white. Associated Minerals include aegirine, analcime, catapleiite, microcline, natrolite and rhodochrosite.