gemstone

Pearl

Nacre (aragonite, CaCO₃, in an organic conchiolin matrix)

AI-generated identification · may be incorrect

A smooth, near-round cream-white bead with strong pearly luster and orient; nacre has Mohs hardness about 2.5–4.5, imperfect cleavage, and specific gravity about 2.60–2.85. The image alone cannot confirm whether it is natural, cultured, freshwater, saltwater, or imitation.

Identified September 12, 2026More gemstone →

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Physical properties

Formation & geological history

Pearls form when mollusks deposit concentric nacre layers around an irritant; cultured pearls are nucleated by humans. Growth commonly takes months to several years in modern freshwater or marine aquaculture, rather than forming as an igneous, sedimentary, or metamorphic rock.

Uses & applications

Used primarily in jewelry and ornamental objects; high-quality natural pearls can be valuable, while common cultured pearls are widely affordable. They are drilled, polished, and sometimes dyed or coated.

Geological facts

Its iridescence results from light interference within microscopic aragonite platelets. A genuine pearl feels gritty against the teeth, whereas glass or plastic imitations usually feel smooth—though this test can damage jewelry.

Field identification & locations

Common sources include Japan, Australia, French Polynesia, China, and the Persian Gulf historically. Check nacre thickness, surface blemishes, drill-hole edges, X-ray structure, and fluorescence; professional testing is needed for authentication.