Barite
Norman, Oklahoma
This specimen measures 16cm x 13cm
Barite BaSO4
Sulfates; Barium sulfate, often with small amounts of strontium
Color and Luster: White, gray, colorless, or shades of yellow, brown, red, blue; vitreous, pearly; streak white
Hardness: 3-3.5
Cleavage: Perfect in one direction, good in a second, and distinct in a third
Fracture: Uneven
Crystals: Orthorhombic; usually thin to thick tabular crystals; also prismatic crystals, divergent groups, compact, lamellar, fibrous, granular
Photo by Mary Sutherland
Descriptions taken from
The Audubon Society Field Guide to North American Rocks and Minerals