By general definition, organic minerals are compounds containing carbon. In other words, they are minerals formed as a result of biological processes. They are not often described as true miranal by mineralogists due to their organic origin.
Coral is skeletal material produced by marine animals. Coral is organic and created by living organisms. When coral polyps die, the hardened skeleton remains and this material is used as a gemstone. Most corals are white, but nature can create coral in many other colors, including the popular orange to red forms. Usually its compound is calcium carbonate.