Black coral is a term given to a group of deep water, tree-like tropical coral related to sea anemone. Though its living tissue is brilliantly colored, black coral takes its name from the distinctive black or dark brown color of its skeleton. Also unique to black coral are the tiny spines that cover the surface of the skeleton, the origin of the nickname little thorn coral. In the Hawaiian language, black coral is called ‘ēkaha kū moana and is the official state gem of Hawaii.