Most shells come from soft-bodied mollusks. Snails, clams, oysters, and others need the hard protection of their shells. This tough outer covering protects the tasty body hiding inside. Other animals, such as crabs and lobsters, also make a tough outer covering, but here we focus on mollusk shells.

How are shells created?

As mollusks develop in the sea, their mantle tissue absorbs salt and chemicals. They secrete calcium carbonate, which hardens on the outside of their bodies, creating a hard shell. ... When a mollusk dies it discards its shell, which eventually washes up on the shore. This is how seashells end up on the beach.

How long does it take for a seashell to form?

Seashells are like that. Some mature mollusks appear simply as bigger versions of their younger selves. Others are so different in grownup guise that even experts mistake them for altogether different shell species. On average, it takes a seashell from one to six years to reach full size and anatomical maturity.