The genus of marine corals known as Corallium are commonly called Red Coral Jewelry or precious corals. This gem is an organic material found in the ocean, and technically speaking, it cannot be classified as a gemstone. We bet you won’t allow your favorite piece of red coral jewelry to sit for long in your jewelry box, as this stone differs from most of the minerals obtained from rock formations. How? Well, red corals are a byproduct of marine polyps. Marine polyps live in both shallow and deep waters and continuously secrete substances to form a hard exterior skeleton to protect themselves.