Fossilized Coral Jewelry: Beneficial in healing pancreatic disorders Fossil Coral is a naturally occurring gemstone which is a result of corals getting replaced with agate. Corals are marine animals whose skeletons are fossilized and preserved to be further used in jewelry pieces. These fossil coral form through a natural process which can take around 20 million years to complete. People address this unique variety with the name tag “agatized Coral” or “agatized fossil coral.” Unlike precious corals, fossil coral is not endangered and is much harder in structure.