the scaly-foot gastropod or magneto snail
is a species of deep-sea hydrothermal-vent snail
This vent-endemic gastropod is known only from deep-sea hydrothermal vents in the Indian Ocean, where it has been found at depths of about 2,400–2,800 m (1.5–1.7 mi).
The shell is of a unique construction, with three layers; the outer layer consists of iron sulfides, the middle layer is equivalent to the organic periostracum found in other gastropods, and the innermost layer is made of aragonite. The foot is also unusual, being armored at the sides with iron-mineralised sclerites.
it is the only known extant animal that incorporates iron sulfide into its skeleton (into both its sclerites and into its shell as an exoskeleton).
https://en.wikipedia.org/wiki/Scaly-foot_gastropod 
