Are shells rocks?
Shale is a rock composed mainly of clay-size mineral grains. These tiny grains are usually clay minerals such as illite, kaolinite, and smectite. Shale usually contains other clay-size mineral particles such as quartz, chert, and feldspar. One of the most striking features of our beaches is seashells. Their whorls, curves, and shiny iridescent insides are …