Crystal & mineral guide
Coral
CaCO₃ (organic)
Organic gem of Mediterranean and Asian jewelry trade — soft and acid-sensitive.
Identify Coral with RockScanAbout Coral
Precious coral (especially red Corallium) has long been cut for beads and carvings. Mediterranean red coral remains a classic reference in Italian and Middle Eastern jewelry. Softness and acid reaction require careful wear. Trade is increasingly regulated for conservation — verify legality and CITES where applicable.
Coral belongs in a crystal identifier workflow because photo cues — color zoning, crystal habit, and surface luster — combine with measurable traits like Mohs 3–4 and specific gravity 2.6–2.7. Use RockScan’s camera to get a first-pass ID, then confirm with the checklist below.
Coral properties
| Mohs hardness | 3–4 |
|---|---|
| Crystal system | Organic aggregate |
| Luster | Dull to vitreous when polished |
| Color | Red, pink, orange, white, black |
| Composition | Calcium carbonate secreted by marine coral polyps |
| Formation | Biological growth in warm shallow seas |
| Occurrence | Mediterranean (Sciacca/Torre del Greco trade), Pacific, Japan |
| Specific gravity | 2.6–2.7 |
| Cleavage | None |
How to identify Coral
- Tree-like growth structures under loupe
- Reacts to dilute acid
- Warm organic feel; softer than glass imitations
Collector notes
- Italian Torre del Greco was a historic coral-cutting center
- Dyed bone and plastic are common coral simulants
Value context: Fine even red Mediterranean material commands the highest jewelry prices.
Coral FAQ
How do you identify Coral?
Coral (CaCO₃ (organic)) is typically recognized by red, pink, orange, white, black color, dull to vitreous when polished luster, Mohs hardness 3–4, and organic aggregate crystal system. RockScan can suggest Coral from a photo and surface these checks on the result card.
What is Coral made of?
Coral composition: Calcium carbonate secreted by marine coral polyps. It forms via biological growth in warm shallow seas and is found in Mediterranean (Sciacca/Torre del Greco trade), Pacific, Japan.
Is Coral valuable?
Fine even red Mediterranean material commands the highest jewelry prices.
