1. n. [Geology]
A type of clay mineral from the kaolin group that forms through the weathering of feldspar and mica group minerals. Unlike some clay minerals like montmorillonite, kaolinite is not prone to shrinking or swelling with changes in water content.
2. n. [Drilling Fluids]
A common two-layer clay that does not swell when exposed to water. Kaolinite is used to make paper, pottery and bricks. It occurs naturally in shale and claystone, and therefore is a common component of drill solids in muds.