Identifying Property

• Color — the visible surface color of the mineral. Useful, but not always reliable because impurities can change color.
• Streak — the color of the mineral in powdered form, usually tested on an unglazed porcelain plate.
• Hardness — resistance to scratching, measured with the Mohs scale from 1 to 10.
• Luster — how the surface reflects light, such as metallic, glassy, pearly, silky, greasy, or dull.
• Cleavage — the tendency to break along flat, predictable planes in the crystal structure.
• Fracture — how a mineral breaks when it does not break along cleavage planes. Examples include conchoidal, uneven, splintery, or fibrous fracture.
• Crystal form / habit — the typical external shape or growth pattern of the crystals, such as cubic, hexagonal, prismatic, fibrous, or massive.
• Specific gravity / heft — how heavy the mineral feels compared with another mineral of similar size. Galena, for example, feels unusually heavy.
• Those eight properties would make a very solid foundation for identifying unknown minerals.