Prehnite is a phyllosilicate of calcium and aluminium. Prehnite crystallizes in the orthorhombic system. Very rarely it does form distinct and individualized crystals-showing a square cross-section.

It is brittle with an uneven fracture. Prehnite has a hardness of 6 to 6.5 on Moh’s scale of hardness. It has a pearly vitreous luster and varies from semitransparent to translucent.

It can be colorless, blue or white or may vary from light green to yellow. It is mostly translucent and rarely transparent. In April 2000, a rare orange Prehnite was discovered at the famous South African Kalahari Manganese Fields.

It is the first mineral to be named after a person. Perhnite was first described in 1789 for an occurrence in Germany and was named after Colonel Hendrik Von Prehn. Extensive deposits of gem quality Prehnite occur in the basalt tableland surrounding Wave Hill Station in Australia.