For the first time, a rare iron mineral has been found in the teeth of an animal - a mollusk also known as a "wanderng meatloaf."

The mollusk chiton, formally known as Cryptochiton stelleri, got its name from its strange appearance: a large, reddish-brown mass that looks like its namesake food out of place. Researchers behind the discovery were surprised to find santabarbaraite - a rare iron mineral - in the chiton's tooth especially since it was only found in rocks, until now. Named for the locality of Santa Barbara in Tuscany, Italy and the patron saint of miners, santabarabaraite is commonly orange, orange-brown, or yellowish-brown when found in nature, according to mining data portal Mindat.

They believe that the discovery is justified since a wandering meatloaf needs especially tough teeth to chew on rocks and scrape of algae growing on its surface, as well as other food materials. A chiton is known for having one of the hardest teeth in nature, as evidenced in a 2010 study in the journal Materials Today, with rows of them attached to a flexible, tongue-like structure called a radula.

Researchers from the Northwestern University present the incredible find in the article "Persistent polyamorphism in the chiton tooth: From a new biomaterial to inks for additive manufacturing" set to appear in the latest Proceedings of the National Academy of Sciences.

Cryptochiton stelleri
(Photo: Jerry Kirkhart via Wikimedia Commons)
Cryptochiton stelleri. You can see the dorsal plates that are hidden by this mollusk. Most Chitons have very visible 8 dorsal plates.

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Never Before in a Biological Context

"This mineral has only been observed in geological specimens in very tiny amounts and has never before been seen in a biological context," says Derk Joester, senior author of the study, in a press release from Northwestern University. He adds that this rare iron mineral has high water content, making it stronger with lower density. Also, researchers believe that this helps strengthen the teeth of the wandering meatloaf without adding too much to the weight.

Joester is a Material Science and Engineering Associate professor in the University's McCormick School of Engineering. The first author of the paper is Linus Stegbauer, a former postdoc fellow in Joester's lab and now a principal investigator at the University of Stuttgart's Institute of Interfacial Process Engineering and Plasma Technology.

Researchers used a variety of analytical processes with help from the Argonne National Laboratory's Advanced Photon Source, as well as with Northwestern's Atomic and Nanoscale Characterization and Experiment Center, both located in Illinois. The tests showed that the teeth of the wandering meatloaf actually contain santabarbaraite, particularly in its upper stylus. The stylus connects the tooth to the radula in the chiton.

Joester likens the chiton's stylus as the root of the human tooth, connecting the tooth cusp to the jaw. He adds that the stylus is "a tough material" that contains extremely small nanoparticles in a structure similar to human bones.

Taking Inspiration from Nature

Drawing inspiration from the incredible structure of the chiton stylus infused with the rare iron mineral, researchers are looking to recreate the material as ink for 3D printing. They plan to fabricate an ink that contains iron and phosphate mixed with a natural substance that comes from a chiton. Once the ink dries up, it creates a hard and durable material.

Explaining how mechanical structures are "only as good as their weakest link," Joester adds how interesting it might be to learn how the wandering meatloaf solves the challenge of connecting an ultrahard material to a soft underlying structure.


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