I'm just going to quote
Wiki straight because it really says it all:
"The scaly-foot gastropod, tentatively Crysomallon squamiferum, is an unusual snail armored with iron-mineral scales. It was discovered in 2001 on the bases of black smokers at the Kairei hydrothermal vent field, on the Central Indian Ridge, just north of the Rodrigues Triple Point; about 2420 meters below the surface. The snail's foot is protected by scale-shaped sclerites composed of the iron sulfides greigite and pyrite; no other animal is known to use iron sulfides in this way."
SCALE MAIL SNAAAAIIILLS
More info at the NatGeo article
here.