gemstone

Cultured pearls

Pearl; predominantly aragonite (CaCO₃) in nacre with organic conchiolin

AI-generated identification · may be incorrect

Hardness about 2.5–4.5 Mohs; cream-white, pearly luster, concentric nacreous layers, and generally round to near-round beads. Pearls are not crystalline masses like ordinary minerals; their aragonite platelets form a layered composite around a cultured nucleus.

Identified September 11, 2026More gemstone →

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Physical properties

Formation & geological history

Cultured in freshwater or marine mollusks when an inserted nucleus or tissue stimulates nacre deposition over roughly 6 months–4 years. They are modern biological gemstones rather than geological rocks, though they qualify here as geological specimens under the requested broad definition.

Uses & applications

Used primarily in jewelry, including necklaces, earrings, and bracelets; value depends on luster, nacre thickness, surface quality, shape, size, and matching. They have little industrial or construction use.

Geological facts

The pictured strand appears to contain cultured pearls, likely freshwater, based on irregular shapes and strong surface luster. Pearls can be damaged by acids, cosmetics, abrasion, heat, and prolonged dryness.

Field identification & locations

Identify by cool, slightly gritty nacre under a gentle tooth test—not recommended for valuable pieces—rather than smooth glassy imitation beads; X-ray testing confirms cultured structure. Common sources include China, Japan, Australia, Indonesia, and French Polynesia.