Fluorite and Sphalerite
Elmwood, Tennessee
This specimen measures 14cm x 13cm x 9cm
Flourite CaF2
Halide; Calcium fluoride, with small amounts of yttrium and cerium
Color and Luster: Violet, blue, green, yellow, brown, bluish black, pink, rose-red, colorless, white; vitreous; streak white
Hardness: 4
Cleavage: Perfect in four directions, forming and octahedron
Fracture: Uneven, brittle
Crystals: Isometeric; usually cubic or as penetration twins; less frequently octahedral and rarely dodecahedral; also cleavage masses, granular, columnar; penetration twins common
Sphalerite ZnS
Sulfide; zinc sulfide, usually with some iron, manganese and cadmium
Color and Luster: Yellow, brown, red, green, black; rarely white or pale gray(Var. cleiophane); resinous, adamantine, submetallic; streak light brown (streak lighter than specimen)
Hardness: 3.5-4
Cleavage: Perfect in six directions
Fracture: Conchoidal; brittle
Crystals: Isometric; tetrahedral and dodecahedral forms common; faces often rounded; also cleavage masses, granular, compact, botryoidal
Photo by Mary Sutherland
Descriptions taken from
The Audubon Society Field Guide to North American Rocks and Minerals