The symmetry of alunite is the same as the members of the Tourmaline Group . Crystals of alunite however do not form prismatic crystals like those of the typical tourmaline mineral. Alunite's crystals are more flattened and resemble nearly cubic rhombohedrons. Color is white or gray to reddish. Luster is vitreous to pearly.
Crystals are transparent to translucent.
Crystals are somewhat scarce, small and usually line the fissures in alunite rocks, more commonly as earthy masses, films or crusts, botryoidal and granular. Fracture is conchoidal to uneven. Hardness is 3.5 - 4. Streak is white. Does not react to acids except to slowly dissolve, unlike dolomite and calcite.