Prehnite
Prehnite is an apple-green to pale green calcium aluminum silicate that fills vesicles (gas bubbles) in basaltic lava. New Jersey's Paterson trap rock quarries are world-famous for producing exceptional prehnite alongside zeolites, datolite, and stilbite — one of the richest zeolite and mineral-in-basalt localities in the world. Prehnite was the first mineral named after a person (Dutch colonel Hendrik von Prehn).
Physical Properties
Chemical Formula
Ca₂Al(AlSi₃O₁₀)(OH)₂
Hardness (Mohs)
6–6.5
Color
Pale green, apple green, yellow-green, rarely colorless
Luster
Vitreous to pearly
Crystal System
Orthorhombic
Streak
White
Cleavage
Good in one direction
Specific Gravity
2.80–2.95
🔍 Field Identification Tips
Apple-green color, vitreous to waxy luster, and barrel-shaped botryoidal masses filling basalt cavities are characteristic. Hardness 6–6.5. Often associated with white/colorless zeolites (stilbite, heulandite) and epidote. Distinguished from jade by luster and crystal habit. The rounded globular surface texture (mammillary habit) is very characteristic.
Varieties & Forms
📍 Where to Find Prehnite in the US
Uses & Applications
Cabochons, carvings, collectors specimens. Highly regarded in the Chinese collector market.
💰 Collector Value Guide
Common rough: $5–$40/lb. Exceptional New Jersey specimens: $30–$300. Gem transparent material: $20–$200/ct.
Find Prehnite With Our Tools
Use the We Lick Rocks app to identify specimens, find dig sites, and connect with local rockhounds.