Group: Silicates - phyllosilicates
Chemical composition: Ca2Al2Si3O10(OH)2
Colors: green, yellow, tan or white
Hardness: 6 to 6.5
Formation: Orthorhombic crystal; forms in tabular, botryoidal masses
Principal Sources: Australia, Scotland, Canada
Special Notes: Prehnite crystallizes in the orthorhombic crystal system, and most oftens forms as stalactitic or botryoidal aggregates, similar to a pom-pom and resulting in ball like crystals. It is the first mineral to be named after someone, was first described in 1789 and named for Colonel Hendrik Von Prehn. Phrenite is often found in conjunction with epidote.