Prehnite
Cedar Mountain Stone Quarry
Mitchells, Virginia

This specimen measures 52cm x 35.5cm x 23cm

Prehnite Ca₂Al₂Si₃O₁₀(OH)₂

Complex silicate; calcium aluminum silicate, often with some iron

Color and Luster: Light green, oil-green, gray, white, colorless; frequently fading upon exposure; vitreous, waxy; streak colorless

Hardness: 6-6.5

Cleavage: Distinct, one direction

Fracture: Uneven

Crystals: Orthorhombic; crystals rare, usually in botryoidal masses, with ridged surfaces marked by edges of curving crystals; also stalactitic, radial fibrous

Note: This "grape cluster" mass of botryoidal crystals weighs 74 lbs

Collected by David Lipscomb

Photo by Mary Sutherland

Descriptions taken from
The Audubon Society Field Guide to North American Rocks and Minerals