Tags: Chemical Substance, Mineral.
Prehnite is a inosilicate of calcium and aluminium with the formula: Ca2Al(AlSi3O10)(OH)2. Limited Fe3+ substitutes for aluminium in the structure. Prehnite crystallizes in the orthorhombic crystal system and most oftens forms as stalactitic or botryoidal aggregates with only just the crests of small crystals showing any faces which are almost always curved or composite.
