Collector-friendly mineral terms covering crystal forms, properties, formation settings, and chemistry basics. Great for accurate IDs, labeling, and comparing specimens.
Applying dilute acid to see if a mineral fizzes (effervesces), indicating carbonate content; commonly used to distinguish calcite and other carbonates from look‑alikes.
A star-shaped light pattern (often 4 or 6 rays) produced by oriented inclusions; typically visible on cabochon-cut stones and used as a descriptive/valuing feature.
Double refraction where light splits into two rays, sometimes producing doubled edges through transparent crystals; an optical clue tied to crystal structure.
A moving ‘cat’s‑eye’ band of light caused by aligned fibers or needle-like inclusions; commonly seen on cabochons and used to describe gemstone appearance.
