A limpet has teeth made from the strongest known natural biological material.
Limpet teeth are tiny structures on a ribbon-like feeding organ called the radula. The teeth scrape algae from hard rocks, so they must withstand repeated abrasion. Research has shown that their iron-mineral fibres are stronger, by tensile strength, than spider silk and many engineered materials.
The strength comes from densely packed goethite fibres embedded in a protein framework. The fibres are extremely small, allowing the material to avoid the flaws that weaken larger structures. Limpets continually replace worn teeth as they feed.
Limpets are marine gastropod molluscs, not clams or insects. Their conical shells help them cling tightly to rocks in the intertidal zone. The impressive tooth material is useful because their grazing lifestyle exposes the radula to constant contact with stone.