Definition: A group of hydrous aluminium phyllosilicate (phyllosilicates being a subgroup of silicate minerals) minerals (see clay minerals), that are typically less than 2micrometres in diameter. Clay consists of a variety of phyllosilicate minerals rich in silicon and aluminium oxides and hydroxides which include variable amounts of structural water.
Definition: Natural freshwater surface streams of considerable volume and a permanent or seasonal flow, moving in a definite channel toward a sea, lake, or another river; any large streams, or ones larger than brooks or creeks, such as the trunk stream and larger branches of a drainage system.
