The "scaly-foot gastropod" is a type of snail that thrives in the hydrothermal vents found deep in the Indian Ocean. And it has a unique property: a magnetic outer shell.
These snails were first discovered during a 2001 survey. It took researchers a while to find the snails because they (the snails) were at the bottom of the ocean, next to hydrothermal vents. It's those vents that gave the snails their special outer shells.
The core of the scaly-foot gastropod looks like the core of any other snail — disgusting and slimy. Go out one layer and it still looks like a common snail, with a calcium carbonate layer around the central goo. In fact, it looks just like a regular snail until you get to the outermost layer.
This layer consists of Fe3S4 and FeS2. The first is a substance called greigite, the other is the well-known pyrite, or "fool's gold." Both of them contain iron, which means that if you wanted to pick this snail up, all you'd have to do is wave a sufficiently strong magnet over it. No other gastropod on Earth has managed to make a shell out of these materials.
The key to the snail's shell is probably the sulphur. It lives near hydrothermal vents, which give off a great deal of hydrogen sulfide. The snails have used this element to make a stronger outer layer to their shells. Until a predator learns to manipulate magnetic fields, they're safe.