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.

Gemstone Properties

Chemical ClassificationOrganic - Calcium carbonate (from marine organisms)
ColorCoral can be white, pink, red, blue, black, and brown. The most prized is the deep red variety, often called 'ox blood.'
StreakDark Blue to Black
LusterWaxy to dull.
OccurrenceItaly (especially the Mediterranean), Japan, and Taiwan.
FormationCoral forms in tropical and subtropical ocean waters through the accumulation of calcareous skeletons of marine polyps.
Mohs Hardness3 to 4.
Specific Gravity2.60 to 2.70.
Diagnostic PropertiesOrganic, often red or pink.
Chemical CompositionCaCO3
Crystal SystemOrganic, not applicable
Optical PropertiesIsotropic (due to its organic nature)
Refractive Index1.486
BirefringenceNone (isotropic due to organic nature)
2V angleNot applicable (organic)
DispersionNot applicable, as coral is organic.