Coral
What is Coral?
Coral is an organic material that is often found in tropical and subtropical oceans. It’s primarily used as a gemstone and is popular for its range of colors including red, pink, and white.
Coral is a unique gemstone that comes in a range of colors including red, pink, and white. Its vibrant hue and unique appearance make it a popular choice for jewelry and decorative items, especially beads and pendants.
| Chemical Classification | Organic - Calcium carbonate (from marine organisms) |
| Color | Coral can be white, pink, red, blue, black, and brown. The most prized is the deep red variety, often called 'ox blood.' |
| Streak | Dark Blue to Black |
| Luster | Waxy to dull. |
| Transparency | Opaque. |
| Occurrence | Italy (especially the Mediterranean), Japan, and Taiwan. |
| Formation | Coral forms in tropical and subtropical ocean waters through the accumulation of calcareous skeletons of marine polyps. |
| Diaphaneity | Opaque |
| Cleavage | None |
| Mohs Hardness | 3 to 4. |
| Specific Gravity | 2.60 to 2.70. |
| Diagnostic Properties | Organic, often red or pink. |
| Chemical Composition | CaCO3 |
| Pleochroism | None. |
| Crystal System | Organic, not applicable |
| Optical Properties | Isotropic (due to its organic nature) |
| Refractive Index | 1.486 |
| Birefringence | None (isotropic due to organic nature) |
| 2V angle | Not applicable (organic) |
| Dispersion | Not applicable, as coral is organic. |