Red Coral (with Hematite and Black Pearl accents)

Physical Properties

Hardness: 3.5-4.0 (Mohs); Color: Salmon pink to deep oxblood red; Luster: Dull to vitreous; Crystal Structure: Amorphous/Organic; Cleavage: None; Specific Gravity: 2.6-2.7

Formation & Geological History

Biogenic formation created by marine polyps in deep-sea colonies. They secrete a hard calcium carbonate skeleton over decades to centuries, primarily in Mediterranean and Pacific waters.

Uses & Applications

Primarily used in jewelry (beads, cabochons), carvings, and ornamental art. Historically used in talismans and traditional medicine.

Geological Facts

Precious coral is considered an organic gemstone, similar to pearls or amber. It has been harvested since antiquity, and 'Oxblood' is the most coveted shade of red.

Field Identification & Locations

Field identification: Look for faint wood-grain-like striations under magnification. It will effervesce (fizz) if touched with a tiny drop of mild acid due to its calcium carbonate composition. Modern specimens are often dyed; check for color concentration in cracks.

Identified on: 4/25/2026

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