Another biogenic gem, coral comes from colonies of marine invertebrates whose exterior shell, made of calcium carbonate, can be fashioned into jewelry and other ornaments.
The most popular coral gemstone is red coral, which exhibits a durable pink or red skeleton. Found mainly in the Mediterranean Sea, red coral is extremely soft, and is often made into beads. Red coral has been found in ornaments from ancient Egyptian and prehistoric European burial sites. Today, red coral is increasingly rare due to over harvesting.
Hawaii’s state gem is black coral, another variation that supposedly wards off injury and evil. Black coral species grow all over the world, and the skeletons can be bleached to create gold coral for a unique look.