The Snail With an Iron Shell That Survives Volcanoes
The scaly-foot snail builds its shell out of actual iron and lives beside boiling volcanic vents nearly 2,000 metres underwater. Here's how it survives conditions that would kill almost anything else.
Most animal armor is built from calcium, chitin, or keratin. One snail decided none of that was tough enough and builds its shell out of actual iron instead, then goes and lives right next to underwater volcanoes for good measure, in the same crushing, lightless depths covered in our look at deep-sea animals with terrifying adaptations.
Meet the Scaly-Foot Snail
The scaly-foot snail, scientific name Chrysomallon squamiferum, lives exclusively around hydrothermal vents in the Indian Ocean, at depths of roughly 2,400 to 2,900 metres, according to Australian Geographic. It’s been found at just three vent fields on the entire planet, a total habitat area roughly the size of two football fields.
Living Metal Armor
The snail’s shell incorporates iron sulfide minerals, primarily pyrite (the mineral known as fool’s gold) and greigite, layered over its normal shell material, according to Forbes. It doesn’t stop at the shell either. The foot the snail uses to move is covered in hundreds of overlapping armored scales called sclerites, also plated with iron sulfide, giving it a look that’s earned it the nickname “sea pangolin.”
The result is genuinely magnetic. The iron content is dense enough that the shell responds to a magnet, an almost unheard-of trait in the animal kingdom.
Why Build a Shell Out of Metal?
Hydrothermal vents are an extraordinarily hostile place to live. The water pouring out of nearby vent chimneys can exceed 350°C, and it’s saturated with dissolved metals and sulfides that would poison most animals, according to Forbes. The scaly-foot snail doesn’t live directly in that scalding water, but it does live close enough that its iron-reinforced armor is thought to help protect it from both the chemical environment and predators navigating the same harsh terrain.
Researchers studying its genome have also found that the same genes responsible for forming its scales and shell are related to genes found in other mollusks, like the beak of a squid or the shell of a chiton, according to ScienceDaily. The scaly-foot snail didn’t invent a new biological trick from scratch, it repurposed existing machinery to build something no other known animal has.
An Endangered Metal Snail
Despite thriving in one of the most extreme environments on Earth, the scaly-foot snail is now listed as Endangered by the IUCN, the first hydrothermal vent species ever assessed that way, according to a 2025 population study. The threat isn’t temperature or toxicity, it’s deep-sea mining. The same vent fields the snail depends on are being targeted for their mineral deposits, and because the species lives in only three known locations, losing even one vent field could be catastrophic for its total population.
Frequently Asked Questions
Is the scaly-foot snail’s shell really made of metal? Yes. Its shell and foot scales incorporate iron sulfide minerals, primarily pyrite and greigite, making it the only known animal to build iron directly into its skeleton.
Where does the scaly-foot snail live? It’s found only at three hydrothermal vent fields in the Indian Ocean, at depths between roughly 2,400 and 2,900 metres.
The scaly-foot snail remains one of the clearest examples in nature of an animal solving an extreme survival problem in a way nothing else on Earth has managed to replicate.
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