Prehnite is calcium alumosilicate that forms in transparent colorless to translucent yellow, yellow-green, and blue-green orthorhombic crystals. It often forms in stalactitic aggregates of globular bubbly crystals clusters. Prehnite has a fascinating crystal formation and the individual crystals sometimes form as perfectly round balls or cylindrical fingers with rounded terminations. It is a relatively durable mineral with a hardness of 6 - 6.5 Mohs. Prehnite has a distinctive pearly luster when it is faceted or polished that helps to distinguish it from Peridot, or Chrysoprase.

Prehnite can often have needles of Epidote inclusions which is misidentified as Rutile or Black Tourmaline. Epidote is a green to black mineral that often forms in tandem with Prehnite. Many other minerals form in clusters with Prehnite including Quartz, Calcite, Apophyllite, Copper and Babingtonite. Prehnite is an affordable gemstone when cut although fine natural specimens can be of higher value if they are of exceptional quality.