This chiton, a marine mollusc the size of a fingernail called Chaetopleura apiculata, has teeth made of magnetite, the hardest material made by a living organism. It has a single muscular foot and a shell made of eight plates. Some species live up to 20 years. Magnetite is an iron oxide, and Chaetopleura apiculata have been able to produce the material in benign ocean water conditions with the iron available from the algae they consume.
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