Clastic rock rich in lithics are called lithic sandstones. Siliciclastic sedimentary rocks are composed of mainly silicate particles derived by the weathering of older rocks and pyroclastic volcanism. While grain size, clast and cementing material (matrix) composition, and texture are important factors when regarding composition, siliciclastic sedimentary rocks are classified according to grain size into three major categories; conglomerates, sandstones, and mudrocks. The term clay is used to classify particles smaller than .0039 millimeters. However, term can also be used to refer to a family of sheet silicate minerals. Silt refers to particles that have a diameter between .062 and .0039 millimeters.
Soil specific surface area and its unbalanced negative electric charges, clay is the most active mineral component of soil. It is a colloidal and most often a crystalline material. In soils, clay is a soil textural class and is defined in a physical sense as any mineral particle less than in effective diameter. Many soil minerals, such as gypsum, carbonates, or quartz, are small enough to be classified as clay based on their physical size, but chemically they do not afford the same utility as do mineralogically-defined clay minerals. Chemically, clay minerals are a range of phyllosilicate minerals with certain reactive