Pearl

Physical Properties

Hardness: 2.5-4.5 Mohs; Color: White, cream, pink, silver; Luster: Pearly (nacreous); Crystal structure: Orthorhombic (microcrystalline); Cleavage: None; Specific Gravity: 2.60-2.85

Formation & Geological History

Biogenic formation within the soft tissue of a living shelled mollusk. Formed when an irritant is trapped inside the shell, causing the mantle to secrete layers of nacre. Age varies by harvest, typically 6 months to several years.

Uses & Applications

Primarily used in jewelry (necklaces, earrings, rings) and as a traditional gemstone. Historically used in medicine and cosmetics in powdered form.

Geological Facts

Pearls are the only gemstones produced by living organisms. The oldest pearl jewelry ever found dates back over 2,000 years to a Persian princess's tomb.

Field Identification & Locations

Identify by the 'tooth test' (feels gritty against teeth) or by looking for overtones of color on the surface. Found in both saltwater and freshwater environments globally, especially in Japan, China, and the South Pacific.

Identified on: 5/1/2026

Mode: Standard