Coral

General Information

Precious coral has been loved and worn by people since the agricultural revolution approximately ten thousand years ago. When groups of people began transitioning from hunting/gathering and began settling, planting crops, and harvesting from the sea, they discovered the beautifully coloured corals washed up on shore and being pulled up in their nets. As it carves easily, it was soon worn as ornaments to display wealth and status. Today, coral is becoming more rare and precious as environmental changes reduce the coral’s habitat.

Quality

Coral belongs to a gemstone group know as organics, as they have a biological origin. There are two forms of gem coral, one in colours of pink, orange, red and white that form when tiny marine creatures called marine polyps secrete a calcium carbonate shell to protect themselves. Coral polyps cluster in enormous colonies, and all of these shells are joined together to form the coral masses. The other form, in colours of black, white or gold, grow like plants or trees.

As coral reefs are a vital part of the world’s ecosystems, it is illegal in many areas to harvest coral directly; coral that has broken away is able to be used in jewellery and decorative items

Treatment

Coral is often waxed to protect the surface of the material; the wax is colourless and does not affect the colour of the coral. A high percentage of coral is treated in this way and so you will always assume this has occurred. Corals can also be dyed, bleached, or glass or plastic impregnated.

Folklore

In Scotland, it is said that coral brings beauty and prosperity to young girls.

Care

As an organic gem material, care must be taken in the cleaning and maintenance of coral. Warm soapy water is an acceptable cleaning solution and an ultrasonic or steam cleaner must never be used. Coral may burn if exposed to a jewellers torch, and is very susceptible to attack by chemicals or solvents. Coral may discolour if worn frequently, so a closed back setting is best to protect the stone.

Scientific Information

Chemical Composition     CaCO₃ (Calcium Carbonate)

Crystal System                N/A

Refractive Index              1.486 - 1.658

Specific Gravity                2.60 - 2.70

Hardness                         3.5 - 4

Cleavage                         None

Fracture                           Irregular, splintery

Lustre                              Dull