:For the town in the United States, see Clay, New York.Clay is a generic term for an aggregate of hydrous silicate particles less than 4 micrometers in diameter. It consists of small crystals of the minerals silica (SiO2) and alumina (Al2O3). These elements, silicon, oxygen and aluminium are the most abundant in the earth's crust. Clay is generally formed by the chemical weathering of silicate-bearing rocks by carbonic acid, but some are formed by hydrothermal activity. Clays are distinguished from other small particles present in soils such as silt by their oblong shape, affinity for water and high plasticity index.
There are three main groups of clays: Kaolinite- SerpentineSerpentine is a group of common rock-forming hydrous magnesium iron phyllosilicate ((Mg,Fe)SiO(OH)) minerals. In mineralogy, serpentine may refer to any of 20 minerals belonging to the serpentine group. Owing to admixture, these minerals are not always ea, Illite , and Smectite . Altogether, there are about thirty different types of "pure" clays in these categories, but most natural clays are mixtures of these different types, as well as other weathered minerals.
Montmorillonite, with a chemical formula of (Na,Ca)0.33(Al,Mg)2Si4O10(OH)2.nH2O, is typically formed as a weathering product of low silica rocks. Montmorillonite is a member of the smectite group.
Clays hardened by fire were the first ceramic, and remain one of the cheapest and most widely used materials to produce even in the present day. Bricks, cooking pots, art objects, spark plugA spark plug is an electrical device that fits into the cylinder head of some internal combustion engines and ignites compressed aerosol gasoline by means of an electric spark. Spark plugs have an insulated wire which is connected with a induction coil or tips, and even musical instruments such as the ocarinaAn ocarina is a wind instrument, closed at both ends to produce an enclosed space, and punctured with four to thirteen finger holes. A mouth tube projects from it, often from the side, and one sound hole is added, usually on the underside of the instrumen are all made with clay. Clay is also used in many industrial processes, such as paperPaper is a thin, flat material produced by the compression of fibres. The fibers used are usually natural and based upon cellulose. The most common material is wood pulp from pulpwood (largely softwood) trees such as pines, but other vegetable fiber mater making, concreteIn general, a concept is considered concrete if it is not abstract: it must be both particular and an individual, and hence occupy both space and time. To say that a physical object is concrete is to say, approximately, that it is a particular individual production, and chemical filterThe term filter may refer to: Filter (chemistry) — a device to separate mixtures Electrostatic Dust Filter Filter (mathematics) — a certain kind of subset of a partially ordered set Filter program — in Unix, any program with standard I/O streams. Any softing.
Varve (or varved clay) is clay with visible annual layers, formed by seasonal differences in erosion and organic content. This type of deposit is common in former glacial lakes from the ice age.
See also
Sedimentary rocks
Silicate minerals
Materials
Art materials
