Spinel
Amity, Orange County
New York
This specimen measures 18cm x 12cm
Spinel MgAl2O4
Oxides; magnesium aluminum oxide, in which magnesium can be partly or completely replaced by iron, zinc, or manganese
Color and Luster: Red, green, blue, brown, black; vitreous, dull; streak white
Hardness: 7.5-8
Cleavage: None
Fracture: Conchoidal, brittle
Crystals: Isometeric; usually octahedrons; cubes and dodecahedrons rare; also granular, compact, disseminate
Photo by Mary Sutherland
Descriptions taken from
The Audubon Society Field Guide to North American Rocks and Minerals