Shell

Shell jewelry

Etymology and history

Mollusk (Sea Shell), common name for members of a phylum of soft-bodied animals are usually with a hard external shell. Familiar Mollusks (Sea Shells) include the clam, oyster, snail, slug, octopus, and squid. The mollusk phylum is the second largest in the animal kingdom, after the arthropods. Earlier estimates of the number of mollusk species sometimes exceeded 100,000, but more recently this figure has been reduced to less than 50,000; the new estimates are

Shell description

A shell is typically made up of three distinct layers. The outer layer, called periostracum, is made up of a protein-like material called conchiolin. The two layers under the periostracum are composed of a framework of conchiolin in which is deposited calcium carbonate (the chief component of limestone) with traces of calcium phosphate and magnesium carbonate. In some mollusks, the molecules of the innermost layer are arranged in such a way that it is hard and iridescent; such a layer is commonly called mother-of-pearl.

Shell in jewelry

Shells have many uses in the arts. Their designs appear in many paintings and other works of art. Jewelry and decorative inlays on musical instruments and other objects are made from mother-of-pearl. Shells can be used as ornaments in themselves or to decorate various objects.

Occurrence

Shell-bearing mollusks are found in sea-water and freshwater, on land, and on plants. Univalves can be found in almost any type of habitat. Bivalves are mostly marine, although some species such as certain clams and mussels are found only in fresh water.