By Chisom Ibemere
Coral is an organic gemstone formed by living organisms compared to other gemstones that are of mineral origin. It is the external skeleton of a tiny, plant-like marine animal called the coral polyp. It occurs from branching, antler-like structures that are created from coral polyps in tropical and subtropical ocean waters. After the death of coral polyps, the skeleton hardened which is used as a gemstone.
Corals are mostly white, but may occur in several other colours, including the popular orange to red forms.
Coral has Amorphous Crystal System with a refractive Index of 1.48 – 1.65 and double Refraction of 172. It is transparent, translucent to opaque with Specific gravity between 2.6 – 2.7 and a vitreous and Waxy Luster and no Cleavage. It has a mohs hardness of 3-4 and made up of Calcium Carbonate.
The Red Coral, also known as Precious Coral is the most used Coral for gemstone. In fact, the color known as coral is derived from the typical pinkish-orange color of many red Coral gemstones.
Coral has been in existence and has been used for thousands of years. It has a very lovely solid colours, it can also have colour zones or swirls, with white, pink, orange, and red being the most prevalent. It has a natural dull appearance and needs to be polished to bring out its glassy lustre. Coral gemstones can be either solid or porous, depending on the polyp formation. Despite Coral’s pretty colours, it is very soft and brittle, and not a durable gemstone. It can be easily scratched and chipped.
Coral has several uses, it is used as cabochons and beads. It can be sculpted into small carvings such as flowers for pins and brooches. Small branches of Coral are sometimes stranded into spiky, dangling necklaces.
Coral occurs in tropical and subtropical saltwater environments. Locations where Corals are produced include the Red Sea, the Midway Islands, the Canary Islands, the Taiwan and Malaysian Coast, the coast of Australia, Italy and Hawaii.
