Glossary Category: Identification Tests (Mohs, etc.)

Applying dilute acid to see if a mineral fizzes (effervesces), indicating carbonate content; commonly used to distinguish calcite and other carbonates from look‑alikes.

Internal crystals, fluids, fractures, or growth features trapped inside a mineral; used to interpret formation conditions and to judge clarity, stability, and aesthetics.

A check for attraction to a magnet (or effect on a compass), which quickly flags strongly magnetic minerals like magnetite and some weakly magnetic species.

A mineral’s scratch hardness on the Mohs scale (1–10), used to compare specimens and narrow identification with simple scratch tests in the field or shop.

How strongly a mineral bends light; measured with a refractometer on a polished surface to separate minerals with similar color, luster, and hardness.

A mineral’s relative density compared to water; ‘heft’ plus a simple specific‑gravity measurement helps separate minerals that look similar.

The color of a mineral’s powdered form left on an unglazed porcelain streak plate; often more reliable than surface color for hand-sample identification.

How a mineral behaves when bent, cut, or crushed (brittle, malleable, sectile, flexible); helpful for distinguishing minerals during hands-on testing.