The Romans awarded the rich red coral found off the coast of North Africa as prizes. Black coral is highly sought after in India and the shell-pink coral of Japan is used as a most expensive decoration.

Corals, in varying shapes and colors, are treasured throughout the world, according to biologists. They are particularly beautiful when they form the coral reefs that harbor an encyclopedia of marine life.The reefs are formed as new, living coral grows in classic finger-like projections from the calcified, porous skeletons of dead coral.

Since reefs can live only under restricted conditions, they are usually found only in tropical areas in the world - the Caribbean, the coast of Brazil the southeastern Pacific, the Indian ocean and Australia.

They live between 150 feet to 300 feet below the ocean surface and flourish in temperatures between 77 and 86 degrees Fahrenheit.

There are three types of reef, according to biologists. The barrier reef usually blocks the lagoon of an island, but may have channels that can be navigated.

Fringing reefs are flat and project outwards from stretches of land, while atolls are curved reefs that protect flat sandy ocean bottom within the ring.

The ancient past of corals is murky. Some evolutionary theorists believe they once creeped along the bottom of the ocean, but then settled for a more sedentary life.