according to blatt, middleton and murray mudrocks that are composed mainly of silt particles are classified as siltstones. in turn, rocks that possess clay as the majority particle are called claystones. in geology, a mixture of both silt and clay is called mud. rocks that possess large amounts of both clay and silt are called mudstones. in some cases the term shale is also used to refer to mudrocks and is still widely accepted by most. however, others have used the term shale to further divide mudrocks based on the percentage of clay constituents. the plate-like shape of clay allows its particles to stack up one on top of another, creating laminae or beds. the more clay present in a given specimen, the more laminated a rock is. shale, in this case, is reserved for mudrocks that are laminated, while mudstone refers those that are not.