Chitons' magnetite teeth

Chitons scrape algae from hard surfaces with a radula, a ribbon bearing many rows of teeth. In several species, the tips of the major teeth are mineralized with magnetite, forming a very hard, wear-resistant composite. Chitons commonly graze on coastal rocks, often in the intertidal zone, so saying they do this “at depth” is misleading; magnetite is also only one component of the tooth. [1–3]