Bioferrite

Bioferrite refers to a wide family of iron-laced protein chains which are naturally produced by much of Oceanyka's fauna, either for defence (as armour plating) or for offense (as claws and fangs). Because iron is hard to work with for biological beings, which don't usually come equipped with a blast furnace, bioferrite is rarer than calcium in terms of biologically useful minerals. Trace amounts of it are, however, rather common in maritime and insect chitin.