Clays exhibit plasticity when mixed with water in certain proportions.
However, when dry, clay becomes firm and when fired in a kiln , permanent physical and chemical changes occur. These changes convert the clay into a ceramic material. Because of these properties, clay is used for making pottery , both utilitarian and decorative, and construction products, such as bricks, wall and floor tiles. Different types of clay, when used with different minerals and firing conditions, are used to produce earthenware , stoneware , and porcelain. Prehistoric humans discovered the useful properties of clay.
Some of the earliest pottery shards recovered are from central Honshu , Japan.
Clay tablets were the first known writing medium. Purpose-made clay balls were also used as sling ammunition.
Clays sintered in fire were the first form of ceramic. Bricks , cooking pots, art objects, dishware , smoking pipes , and even musical instruments such as the ocarina can all be shaped from clay before being fired. Clay is also used in many industrial processes, such as paper making, cement production, and chemical filtering.
Until the late 20th century, bentonite clay was widely used as a mold binder in the manufacture of sand castings. Clay, being relatively impermeable to water, is also used where natural seals are needed, such as in the cores of dams , or as a barrier in landfills against toxic seepage lining the landfill, preferably in combination with geotextiles. Studies in the early 21st century have investigated clay's absorption capacities in various applications, such as the removal of heavy metals from waste water and air purification.
Traditional uses of clay as medicine goes back to prehistoric times. An example is Armenian bole , which is used to soothe an upset stomach. Some animals such as parrots and pigs ingest clay for similar reasons.
Journal list menu
Clay as the defining ingredient of loam is one of the oldest building materials on Earth , among other ancient, naturally-occurring geologic materials such as stone and organic materials like wood. Also a primary ingredient in many natural building techniques, clay is used to create adobe , cob , cordwood , and rammed earth structures and building elements such as wattle and daub , clay plaster, clay render case, clay floors and clay paints and ceramic building material.
Clay was used as a mortar in brick chimneys and stone walls where protected from water. From Wikipedia, the free encyclopedia. A finely-grained natural rock or soil containing mainly clay minerals. For other uses, see Clay disambiguation. This section needs expansion. You can help by adding to it.
April Main article: Clay mineral X-ray diffraction. Earth Sciences department, University College London. Archived from the original on 27 January Open Access.
Clay | geology | oguzoperip.ga
Ilgen, R. Common silicate materials such as quartz, feldspars, and volcanic glasses, as well as carbonates, noncrystalline iron oxides, and primary clay minerals, are transformed during diagenesis into more stable clay minerals mainly by dissolution and recrystallization. The formation of bentonite beds containing smectite-group clay minerals including montmorillonite and fuller's earth a type of clay mineral deposit that has high capacity to absorb water may occur primarily by diagenesis, although some deposits may also form by hydrothermal processes.
Bentonite beds usually form from altered volcanic ash, but other types of rock may also serve as sources. The absorptive properties of bentonites and fuller's earth make them ideal for such diverse uses as drilling mud; foundry-sand bond; binder for pelletizing iron ore and bleaching liquids; absorbents for oil, grease, and animal waste; and carriers for pesticides and fertilizers.
Bentonite is also used as a soil liner for environmental containment applications and with polyacrylamide for making paper. Weathering of rocks and soil is the primary way that clays and clay minerals form at the Earth's surface today.
Clay Minerals Group
The weathering process involves physical disaggregation and chemical decomposition that change original minerals to clay minerals; weathering is uneven, and many stages of breakdown may be found in the same clay sample. Factors governing rock weathering and soil formation include the initial type of rock, the ratio of water to rock, the temperature, the presence of organisms and organic material, and the amount of time.
The types of clay minerals found in weathering rocks strongly control how the weathered rock behaves under various climatic conditions such as humid-tropical, dry-tropical, and temperate conditions. Kaolinite is found in most weathering zones and soil profiles. Montmorillonites, which are chemically more complex than kaolinites, are common in the lower parts of weathering profiles, nearer the rock, where chemistry exerts a strong control on mineralogy.
Complex mixed-layer clay minerals such as illite-smectites are abundant in clay assemblages that develop from mica-bearing precursor rocks, such as the granite plutons that occur in temperate regions of the Northeastern United States. For example, a large component of soils formed by weathering of granites may consist of metastable muscovite, biotite, and chlorite.
These minerals will alter progressively to clay minerals. Industrial minerals, such as clays, sand, gravel, and crushed stone, are raw materials used for building and maintaining infrastructure, agriculture, and mitigation of environmental problems.
Because of the many uses for industrial minerals in our society, land management agencies have an increasing need for better geologic and mineralogic data on industrial minerals. The USGS supports studies to understand the geology of these deposits, the surficial environments, and the processes by which these deposits form. The USGS and industry cooperators are initiating petrologic, mineralogic, and geochemical studies to better determine how economic clay deposits form. A special emphasis of these studies is to characterize the weathering portion of the life cycle of a clay deposit.
Regional data bases such as the Southeastern United States clay deposit data base are being developed that contain geologic and geochemical information necessary to establish environmental characteristics that affect the use of clays and clay minerals. Environmental characteristics include the nature and distribution of inorganic contaminants, such as metals and metalloids like arsenic, iron, and lead, in clay-bearing rocks.
These environmental factors have the potential to affect the use of clays in natural and industrial applications.