Organic gemstone / Sedimentary mineraloid
Precious Coral
Corallium rubrum (Calcium carbonate with trace carotene)
Hardness: 3.5 - 4 on Mohs scale; Color: Pink to deep red (oxblood); Luster: Dull (natural) to vitreous/waxy (polished); Structure: Branching skeletal forms; Specific Gravity: 2.6 - 2.7
- Hardness
- 3
- Color
- Pink to deep red (oxblood)
- Luster
- Dull (natural) to vitreous/waxy (polished)
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Physical properties
Hardness: 3.5 - 4 on Mohs scale; Color: Pink to deep red (oxblood); Luster: Dull (natural) to vitreous/waxy (polished); Structure: Branching skeletal forms; Specific Gravity: 2.6 - 2.7
Formation & geological history
Formed by marine polyps in deep-sea colonies. The calcium carbonate skeletons accumulate over hundreds of years. Most commercial sources are from the Mediterranean Sea or the Pacific Ocean near Japan and Taiwan.
Uses & applications
Primary use in fine jewelry (beads, cabochons, carvings) and as a traditional organic gemstone. High-quality pieces are central to Mediterranean and Tibetan jewelry arts.
Geological facts
Unlike surface reef corals, precious coral grows in darkness at depths of 10 to 300 meters. It has been used as a protective amulet and currency since ancient Roman times.
Field identification & locations
Identify by looking for small 'wood grain' striations on the surface under magnification; dyed imitations will lack this structure. Found in deep marine environments. Avoid pieces that look excessively uniform or display air bubbles, which indicate glass or plastic fakes.
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