Coral are marine invertebrates that secrete calcium carbonate to favorably regulate the pH of the ocean water that surrounds them. This creates a hard skeleton around them, with many coral building coral reefs. They get their energy and nutrients from single-cell algae that inhabit their tissues. Such algae need sunlight to grow, meaning coral lives in shallow clear waters. The mineral skeleton secreted by coral also contains magnesium and many other trace minerals naturally found in the ocean, making coral minerals a broad spectrum mineral supplement.
Plain calcium carbonate is found in most rocks. High amounts occur in limestone, chalk, and granite. It is in many ocean shells. And it can readily be synthesized from calcium oxide.
Coral minerals, even though they are carbonates, are different than rock-based calcium carbonate. They are geometrically structured mineral arrangements created by a living organism, making them organic minerals with unique properties. The latest advanced imaging science shows they have organic matrix molecules embedded in the mineral crystals; this is far different than calcium from rock. A second group of researchers has also confirmed the transfer of organic molecules into the calcium structure. Technically, this means that coral minerals are the highest mineral content food that is known, sort of like picking a mineralized apple from a coral tree.