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Prehnite
Cedar Mountain Stone Quarry
Mitchells, Virginia
This specimen measures 52cm x 35.5cm x 23cm
![](minerals\+Grapecluster.jpg)
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