mineral

Spiny Oyster Shell

Spondylus (Calcium Carbonate, CaCO3)

Hardness: 3.5-4.0 (Mohs scale), Color: Orange, red, purple, white; Luster: Pearly to Vitreous; Crystal Structure: Trigonal (as Calcite) or Orthorhombic (as Aragonite); Specific Gravity: 2.7-2.9

Hardness: 3
Color: Orange, red, purple, white
Luster: Pearly to Vitreous

Identified May 9, 2026More mineral →

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Physical properties

Hardness: 3.5-4.0 (Mohs scale), Color: Orange, red, purple, white; Luster: Pearly to Vitreous; Crystal Structure: Trigonal (as Calcite) or Orthorhombic (as Aragonite); Specific Gravity: 2.7-2.9

Formation & geological history

Biogenic formation through marine mollusk shell growth in tropical waters. While not a mineral in the geological sense, it is treated as a biogenic gemstone used alongside minerals in jewelry.

Uses & applications

Used primarily in jewelry, lapidary arts, and Southwestern/Native American beadwork and inlay.

Geological facts

Spiny Oyster is not an oyster but a 'thorny oyster' or Spondylus, more closely related to scallops. It has been used as a form of currency and high-status jewelry for over 2,000 years in Andean and Mesoamerican cultures.

Field identification & locations

Identify by its vibrant tiered color bands and shell-like texture. In its raw form, it is covered in long spines. Commonly found in the Sea of Cortez off Baja California and the Gulf of Mexico.

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