Hardness : 3
Specific Gravity : 2.68
Refractive index : 1.49 - 1.6
Doubly Refracting (bi-refraction) : Not Availa
Coral is among the most ancient of gem materials, used for adornment since prehistoric times. Coral inlays and ornaments have been found in Celtic tombs from the Iron Age. It's also the height of fashion today; its bold tones, so flattering against the skin, add a modern shot of strong color that adds drama to everything you wear. Always effective complementing black, white, brown, and khaki shades, coral is unforgettable when worn with other strong colors.
Coral is an organic gem, calcium carbonate with a trace of carotene, deposited by tiny sea creatures living in the depths of warm seas in huge colonies. It grows in branches that look like underwater trees. Most coral used in jewelry is found in the Mediterranean Sea or in the Pacific off Japan and Taiwan.
Coral was long thought to be a powerful talisman that could stop bleeding, protect from evil spirits, and ward off hurricanes. The ancient belief in the protective and invigorating powers of coral lives on in the traditional present of red coral necklaces for small children. Coral is one of the seven treasures in Buddhist scriptures and Tibetan Lamas use coral rosaries.
When you say the word coral, most people think of the coral reefs in the South Pacific like the Great Barrier Reef off Australia. However, these coral reefs are formed by a different species than the coral traditionally used in jewelry.
Fragile Coral trees were once brought to the surface by means of drag nets. But today, the harvesters use more environmentally sound methods: deep-sea divers collect the branches by hand. In the next step, the pieces are cleaned, sorted, and sawed into pieces. Most coral is set into inlays, beads, carvings, or cabochon shapes.
The most valuable colors of coral are red, black, and pale pink, which is known as angel skin coral.
Good quality Coral has an even color and has no fissures, spots, bands or cavities. Since genuine untreated Coral is rare, it is valuable.
Coral is commonly enhanced to improve its color and durability. White coral is bleached. Pink coral is permeated with a colorless wax and orange coral is stabilized with plastic. Black coral is sometimes bleached to create gold coral. Occasionally, red coral is dyed to deepen or uniform its color. All commonly used forms of coral enhancement are stable.
Special care is required for coral regardless of whether it is enhanced. A soft and porous gem, coral scratches and abrades easily and chlorine, alcohol, ammonia, nail polish remover, and other chemicals can damage it. Remove coral rings when washing and moisturizing your hands. Avoid exposing your coral to extreme temperatures. It may gradually change color from everyday wear.
As an organic gem, coral is softer than other gem materials and should be stored away from other gemstones to prevent scratches. To clean coral, wipe it gently with a moist soft cloth.