gemstone

Natural Freshwater Pearl

Calcium Carbonate (Aragonite and Calcite), CaCO3

Hardness: 2.5 - 4.5 on the Mohs scale. Color: White, cream, silver, or iridescent. Luster: Pearlescent, nacreous. Crystal Structure: Orthorhombic (aragonite platelets). Cleavage: None. Specific gravity: 2.60 - 2.85.

Hardness: 2
Color: White, cream, silver, or iridescent
Luster: Pearlescent, nacreous

Identified August 2, 2026More gemstone →

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Physical properties

Formation & geological history

Formed organically within the soft tissue (mantle) of a mollusk (specifically freshwater mussels in family Unionidae) as a defense mechanism against a foreign irritant, secreting layers of nacre over time.

Uses & applications

Used primarily in fine jewelry, necklaces, rings, and earrings. High value among collectors of natural pearls.

Geological facts

Unlike saltwater pearls which are predominantly cultured with bead nuclei, many freshwater pearls are non-nucleated 'tissue-nucleated' pearls, resulting in solid nacre. Natural pearls are exceedingly rare compared to cultured varieties.

Field identification & locations

Identified by its organic nacreous luster, irregular baroque shape, and warm tactile feel. Found globally in freshwater rivers and lakes, particularly historically in North American rivers.

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