Datolite
Luck Quarry
Loudoun Co, Virginia
The largest individual crystal on this specimen is 2cm in height
Datolite CaBSiO4(OH)
Complex silicate; calcium borosilicate
Color and Luster: Greenish to colorless white, with yellowish reddish, grayish tinge; viteous, dull, greasy; streak colorless
Hardness: 5-5.5
Cleavage: None
Fracture: Uneven, conchoidal
Crystals: Monoclinic, usually shortprismatic to blunt wedge-shaped complex crystals; also fine-grained porcelain-like masses often botryoidal
Photo by Mary Sutherland
Descriptions taken from
The Audubon Society Field Guide to North American Rocks and Minerals