Crystal Identification Guide: Identify Your Crystal by Color & Hardness

Found a crystal in a drawer, inherited a collection, or bought something unlabeled at a market? This tool narrows it down the way mineralogists do: start with color, then confirm with hardness, luster, and a few simple tests you can run at home. No lab required.

The Four Field Tests

Color alone is never enough — many minerals share a shade. These four tests separate look-alikes:

• Scratch test (Mohs hardness). A fingernail scratches up to about 2.5, a copper coin about 3.5, a steel blade about 5.5. Anything that scratches glass is roughly 5.5 or harder — the whole quartz family (amethyst, citrine, rose quartz, smoky quartz) passes this easily, while calcite, selenite, and fluorite fail it. Always test an inconspicuous spot.
• Streak test. Drag the stone across unglazed ceramic (the back of a tile works). Hematite leaves a red-brown streak no matter how silver it looks; pyrite leaves greenish black, while real gold streaks yellow.
• Weight and temperature. Real stone feels cold and dense in the hand. Resin and plastic imitations feel warm and light; glass warms quickly.
• Loupe and UV. Round air bubbles under 10x magnification mean glass, not crystal. A UV lamp helps too — mangano calcite, for example, glows bright pink.

Common Imposters to Rule Out

Some of the most-sold "crystals" aren't what the label says. Bright orange "citrine" points are usually heat-treated amethyst. Perfectly swirled lightweight "malachite" is often resin — our malachite guide covers the tells. Nearly all bargain "moldavite" is molded green glass, and dyed howlite frequently stands in for turquoise and lapis. For the full methodology we use when buying inventory, see the 2026 mineralogical authenticity guide.