Pearl

Physical Properties

Hardness: 2.5-4.5; Color: White, cream, silver, black, pink; Luster: Pearly (iridescent); Crystal structure: Orthorhombic (Aragonite plates); Specific gravity: 2.60-2.85

Formation & Geological History

Biogenic formation; formed within the soft tissue of a living shelled mollusk as a defense mechanism against irritants by secreting layers of nacre.

Uses & Applications

Predominantly used in jewelry, fashion ornamentation, and historically in cosmetics or medicine (pearl powder).

Geological Facts

Unlike minerals formed in the earth, pearls are organic gemstones. The 'tooth test'—rubbing a pearl against your teeth—is a classic way to detect grittiness, which indicates a real pearl versus a smooth plastic fake.

Field Identification & Locations

Identify by its unique luster (orient) and surface temperature (cool to the touch). Found in oceans and freshwater lakes/rivers worldwide. Highly valued for its symmetry and 'clean' surface.

Identified on: 4/21/2026

Mode: Standard