Zinc-Schefferite

Resistance to being scratched, ranked on the Mohs scale from 1 (talc, marked by a fingernail) to 10 (diamond, scratches everything below it). The classic field test.

Whether and how much light passes through a mineral, from transparent (you can see through it) to translucent, then opaque.

The hue of the mineral itself. Often unreliable for identification — many species occur in several colours depending on trace impurities or radiation damage.

How a mineral resists breaking, bending, or crushing. Brittle snaps cleanly, malleable hammers into sheets, sectile slices like soft metal.

The tendency to split along flat planes that match the crystal's atomic structure. Described by quality (perfect, good, poor) and direction.

The shape of a broken surface that doesn't follow cleavage — conchoidal (curved, like broken glass), uneven, hackly, or splintery.

How the mineral glows under short- and long-wave ultraviolet lamps. Some species fluoresce in spectacular colours invisible to the naked eye.

Splitting along planes of weakness that aren't true cleavage — usually caused by twinning or solid-state pressure.

Chemical elements that make up the mineral's ideal formula, listed by atomic symbol with their share of the total mass.