gemstone

Natural freshwater pearls

Pearl (nacreous calcium carbonate; chiefly aragonite, CaCO₃)

AI-generated identification · may be incorrect

Hardness about 2.5–4.5 Mohs; rounded, strongly iridescent bronze-gold surfaces with characteristic overlapping nacre layers and mostly nonuniform shapes. Pearls have no crystal form visible externally and are relatively light, with specific gravity about 2.60–2.85.

Identified August 17, 2026More gemstone →

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Physical properties

Formation & geological history

Formed when a freshwater mussel deposits concentric nacre around an irritant or tissue fragment; usually cultivated over several years in rivers, lakes, and ponds, commonly from modern Holocene deposits.

Uses & applications

Used primarily in jewelry and ornamental beadwork; valuable for luster, surface quality, size, color, and matching. They are organic gemstones rather than igneous, sedimentary, or metamorphic rocks.

Geological facts

The pictured beads appear to be baroque or near-round freshwater pearls, possibly dyed or naturally bronze-colored. Nacre is made of microscopic aragonite platelets bound by conchiolin.

Field identification & locations

Identify by a gritty feel when gently rubbed against a tooth, layered nacre, and lack of glassy uniformity; avoid damaging tests. Common sources include China, Japan, and the Mississippi basin.