sedimentary
Red Coral (Precious Coral)
Corallium rubrum (Calcium Carbonate, CaCO3)
Hardness: 3.5-4.0 (Mohs); Color: Salmon pink to deep red; Luster: Vitreous to dull; Crystal structure: Trigonal (microcrystalline); Cleavage: None; Specific Gravity: 2.6-2.7
- Hardness
- 3
- Color
- Salmon pink to deep red
- Luster
- Vitreous to dull
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Physical properties
Hardness: 3.5-4.0 (Mohs); Color: Salmon pink to deep red; Luster: Vitreous to dull; Crystal structure: Trigonal (microcrystalline); Cleavage: None; Specific Gravity: 2.6-2.7
Formation & geological history
Formed by marine polyps that secrete calcium carbonate to build their skeletons. Over centuries, these secretions accumulate into branch-like structures in subtropical/tropical marine environments.
Uses & applications
Primarily used in fine jewelry (necklaces, beads, cabochons), carvings, and as a collectible gemstone.
Geological facts
Natural red coral has been harvested and traded since ancient times. It is an organic gemstone, meaning it is derived from living organisms rather than geological processes alone.
Field identification & locations
Identify by looking for faint wood-grain patterns or 'growth rings' on the surface of beads. Beware of dyed plastic or glass imitations; real coral may react with weak acids (effervesce).
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