
gemstone
Pearl oyster shell with cultured pearls
Mollusk shell (likely Pinctada spp.) containing aragonite pearls, CaCO₃
AI-generated identification · may be incorrectThe specimen appears to be a polished, nacre-lined shell holding small cultured pearls. Nacre is aragonite with organic conchiolin; hardness about 3–4 Mohs, pearly luster, iridescent white-to-cream colors, and no true cleavage.
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Physical properties
The specimen appears to be a polished, nacre-lined shell holding small cultured pearls. Nacre is aragonite with organic conchiolin; hardness about 3–4 Mohs, pearly luster, iridescent white-to-cream colors, and no true cleavage.
Formation & geological history
Pearls form when a foreign irritant or implanted nucleus is enclosed by successive nacre layers inside a pearl oyster; the shell is biogenic calcium carbonate. Cultured pearls generally form over months to several years in modern aquaculture, rather than representing an ancient geological deposit.
Uses & applications
Pearls are used in jewelry and ornament, while shells are used decoratively and historically as buttons or inlay. Value depends strongly on pearl size, roundness, surface quality, nacre thickness, and provenance.
Geological facts
Pearl color can be altered by species, water chemistry, diet, and treatments. The visible shell and pearls are biological geological materials, though the displayed pearls may be human-cultured.
Field identification & locations
Identify by layered nacre, pearly luster, concentric growth lines, and pearls that feel gritty rather than glass-smooth against a tooth; avoid this test on valuable pieces. Common sources include Japan, China, French Polynesia, Australia, and Southeast Asia.
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