Why Are Seashells Different Colors?

The seashells we find on the beach come in all shapes, sizes, and colors. Before they washed up on shore, those shells were the exoskeletons of marine invertebrates, mollusks, built by the animal to provide protection and a place to live.

Mollusks build and enlarge their shells as they grow. The shells are made largely of calcium carbonate with a pinch of protein (think of a construction site: the protein is the rebar that reinforces and supports everything, while the calcium carbonate is the cement poured over it to fill out the structure). Unlike the shells other animals, seashells are not made of living cells, nor do they have blood vessels or nerves.

Calcium carbonate, the main shell ingredient, is white. The different colors of shells come from the water in which the organism lives and its diet. For example, shells found in the warm waters of the Caribbean are more colorful than those of Maine thought largely due to the greater diversity of food sources in tropical waters. In addition, the color of a mollusk’s shell can also serve as camouflage, keeping it safe from predators. There are also shells that are colorful and shiny; this iridescent coating is called nacre and is produced by some bivalves (mussels, oysters, and clams) to protect their soft bodies from irritants and parasites. It is also the same material that creates a pearl – for more information on how a pearl is made, click here.

The next time you stroll along a beach, remember that every shell has a story to tell!