The radular teeth of Cryptochiton stelleri were studied in great detail over fifty years ago. Ultrastructure and development of iron mineralization in the radular teeth of Cryptochiton stelleri (Mollusca) ... Authors. K M Towe, H A Lowenstam.
The predominant mineral is magnetite Fe3O4., with the iron derived from the storage iron protein, ferritin. What these authors have found is a crystographically amorphous hydrous iron phosphate that is not as hard as magnetite. This paper adds very little to what was already known about this mollusk.