The hard skeleton of red coral branches is naturally matte, but can be polished to a glassy shine. It exhibits a range of warm reddish pink colors from pale pink to deep red. Owing to its intense and permanent coloration and glossiness, precious coral skeletons have been harvested since antiquity for decorative use. Coral jewellery has been found in ancient Egyptian and prehistoric European burial sites and continues to be made to the present day.
The two precious gemstones derived from biologigal sources, coral and pearl, although drastically different in appearance, are chemically very similar. Both are mostly calcium carbonate deposited by marine invertebrates.