Mineral Identification

Hardness, luster, cleavage, and streak tests for common minerals

Minerals are identified by physical properties, not appearance alone. Mohs hardness scale (1-10) ranks scratch resistance: talc (1), gypsum (2), calcite (3), fluorite (4), apatite (5), feldspar (6), quartz (7), topaz (8), corundum (9), diamond (10). Luster describes how light reflects: metallic, vitreous (glassy), pearly, silky, or earthy. Streak is the color of powdered mineral on unglazed porcelain — often different from the mineral's apparent color. Cleavage describes how minerals break along flat planes determined by crystal structure; fracture describes irregular breaking. These properties together form a diagnostic fingerprint for each mineral.