The loss of coral to such animals is usually balanced by the development of new coral colonies and the growth of old ones. Scientists are trying to determine what has caused this starfish to become so numerous. Precious and gorgonian corals. Other kinds of coral, in addition to stony corals, are found in the world's oceans. These corals are also colonies of polyps, but the skeletons they form are internal rather than external.
Precious coral is a species valued for jewelry.
It has a hard core that can be polished. Polishing brings out beautiful red, rose, or pink colors. Craftworkers carve it into beads and other ornaments. Precious coral grows in bushlike formations in the Mediterranean Sea and Sea of Japan. Gorgonian corals have internal skeletons of a flexible, horny substance.