Publisher's Synopsis
With grains smaller than 4 micrometers (m), clay is a soft, loose, earthy substance. Rocks containing the mineral group feldspar, also referred to as the "mother of clay," weather and erode over extremely long periods of time, resulting in its formation. As a result of hydrolysis, or the reaction of water with feldspar, clay minerals like kaolinites and smectites, which are the main minerals in kaolin clays, are created (the principal minerals in bentonite clays).