Prehnite

Prehnite is an inosilicate of calcium and aluminium. It most often forms as stalactitic or botryoidal aggregates, with only just the crests of small crystals showing any faces, which are almost always curved or composite. Prehnite is brittle with an uneven fracture and a vitreous to pearly luster. Its hardness is 6-6.5, In April 2000, rare orange prehnite was discovered in the Kalahari Manganese Fields, South Africa. Prehnite is mostly translucent, and rarely transparent.