Many organisms can produce minerals or mineralized tissue. A well-known example is nacre, which is used in jewelry because of its iridescent colors. Chemically speaking, its formation begins with a mollusk extracting calcium and carbonate ions from water. However, the exact processes and conditions that lead to nacre, a composite of biopolymers and platelets of crystalline calcium carbonate, are the subject of intense debate among experts, and different theories exist.
