Cassiterite
Herbb II Pegmatite
Powhattan Co, Virginia
This specimen measures 8.5cm x 7cm
Cassiterite SnO2
Simple Oxide; tin oxide, often with some iron
Color and Luster: Brown, black; rarely yellow, gray; greasy or adamantine to dull; streak white to light brown
Hardness: 6-7
Cleavage: Distinct
Fracture: Uneven, brittle
Crystals: Tetragonal, generally in short prismatic twinned crystals; also can be granular, desseminated, reniform with radiating fibrous structure(wood-tin)
Note: Largest known single crystal to come from North America
Photo by Mary Sutherland
Descriptions taken from
The Audubon Society Field Guide to North American Rocks and Minerals