Clastic rock The term "mud" is used when clay and silt particles are mixed in the sediment; "mudrock" is the name of the rock created with these sediments. Furthermore, particles that reach diameters between .062 and 2 millimeters fall into the category of sand. When sand is cemented together and lithified it becomes known as sandstone. Any particle that is larger than two millimeters is considered gravel. This category includes pebbles, cobbles and boulders. Like sandstone, when gravels are lithified they are considered conglomerates. Conglomerates are coarse grained rocks dominantly composed of gravel sized particles that are typically held together by a
Parent material eventually settle near the mouth of the river. Lake deposited parent material is called lacustrine parent material. Beach ridges may be present where glacial lakes once washed up sand. Lacustrine material is well sorted and fine-textured, having finer silts and clays. Soils formed from lacustrine parent material have low permeability in part because of this high clay content. Ocean deposited parent materials, called marine sediments, are collections of material that have been carried by rivers and streams to the ocean and eventually sink to the bottom. Such materials can vary in texture. Collections of large rock fragments that have traveled