Fluorite, Sphalerite and Barite
Elmwood, Tennessee

This single crystal of fluorite measures 5cm on edge


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


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

Note: Specimen donated by W. A. N. Severance

Photo by Mary Sutherland


Descriptions taken from
The Audubon Society Field Guide to North American Rocks and Minerals