Characteristics of Prehnite:

Chemical Name: Calcium A\aluminum silicate hydroxide

Formula: Ca2Al2Si3O10(OH)2 

Colors: Green, yellow, tan, white

Structure: Orthorhombic

Hardness: 6-6.5

Specific Gravity: 2.8-2.9

Refractive Index: 1.61-1.67

Lustre: Vitreous

Streak: White

Locations: Canada, Portugal, Germany, Japan, USA, Australia, Scotland

What is Prehnite? 

Prehnite is usually found as globular, spherical, or stalactitical aggregates of fine to coarse crystals. Rare individual crystals are often short and stumpy, and have square cross-sections, while some pale yellow-brown fibrous materials shows a cat’s-eye effect when cut en cabochon. Prehnite is sometimes faceted, but the stones are almost always translucent rather than transparent; faceted stones tend to be small and are cut only for collectors and museums. Semi-transparent Prehnite comes from Australia and Scotland, where the occasional near-transparent piece is found.