Mineral Identification
Hardness, luster, cleavage, and streak tests for common minerals
How it works
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.
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Step-by-step
- Select a mineral sample and perform tests.
- Compare results against the mineral database to identify the unknown.
- Complete all four tests for the most accurate identification.
Frequently asked questions
- A mineral scratches glass (hardness ~5.5) but not quartz. What is its approximate hardness?
- Between 5.5 and 7 on the Mohs scale — could be feldspar (6) or similar.
- A gold-colored mineral has a black streak. Is it gold or pyrite?
- Pyrite — real gold has a golden-yellow streak, while pyrite ('fool's gold') has a dark greenish-black streak.