Sedimentary clay

Secondary clay, also known as sedimentary clay, transported clay, or potter s clay, is a mixture of clay and nonclay particles. After it is formed, much clay is... 

Hamilton (1959) has shown that a 150-700 meter-thick layer of unconsolidated sediments exists even on most deep sea floors. Let us consider a little more closely then the difference between the "open" sea situation, where sedimentary clays are in contact with sea water of roughly constant composition and an unconsolidated sediment which contains a pore fluid. 

Primary clay, known as kaolin, is found in the same place as the parent rock. Kaolin is formed by the weathering of feldspar. Kaolins are coarse in particle size and therefore nonplastic compared to most sedimentary clays. Kaolins are relatively free of mineral impurities such as iron. 

Aluminum is present in many primary minerals. The weathering of these primary minerals over time results in the deposition of sedimentary clay minerals, such as the aluminosilicates kaolinite and montmorillonite. The weathering of soil results in the more rapid release of silicon, and aluminum precipitates as hydrated aluminum oxides such as gibbsite and boehmite, which are constituents of bauxites and laterites (Bodek et al. 1988). Aluminum is found in the soil complexed with other electron rich species such as fluoride, sulfate, and phosphate. 

Pottery is produced by the conversion of sedimentary clay (produced by the weathering of rocks) into hard rocklike objects. The clay minerals, which were formed by the chemical decomposition of certain rock-forming minerals, contain trace elements. The sediments in which these clays are found, however, also contain fragments of the primary minerals from the parent rock (including grains of silica sand). These detrital components, which result from the physical and chemical breakdown of minerals, are often accompanied by authigenic minerals that are chemically precipitated from aqueous solutions. In some ceramics, additional components were added as temper during production. 

In the HNO3 extract of Austrian soils above the crystalline in the Bohemian massive, a mean of 0.5 mg/kg was found. Above sedimentary clays and gravels from the tertiary between the Alps and the Danube, a medium value of 0.2 mg/kg was found, and in the Northern limestone Alpine region, a somehow broadened distribution with a mean of 0.36 mg/kg (Hofer et al., 1990). 

Other clay minerals are also able to bear a clear climatic message, as for instance the amount of random mixed layers and altered smectite in temperate regions, the crystalline status of illite in temperate to warm regions, and the abundance of soilforming Al-Fe smectite in subarid regions. Detailed measurements on X-ray diffraction diagrams, electron microscope observations and geochemical analyses allow precise characterization of the different continental climatic environments from data obtained on detrital sedimentary clays. 

The geologist recognizes two main types of clay, residual and sedimentary. Residual clays are those which have not been transported by natural agencies, but have remained in their place of origin, such as the Cornish china clays, that are found with the granite rock from which they were formed by hypogenic action. Sedimentary clays are those that have been removed from their... 

The method adopted for extracting sedimentary clays depends on the depth of the clay seam, the hardness of the clay, the depth... 

Fireclays are sedimentary clays that were laid down in the Carboniferous Period, most of them being found in the Coal Measures. Although the name fireclay suggests a clay that can withstand heat (i.e. a refractory clay) a large proportion of the so-called fireclays are not very refractory, but are used for making sanitary fireclay, buff tiles, engineering bricks, etc. 

The clay minerals are basically described as hydrous silicates and can be divided into two types on the basis of their natural locations, i.e., (i) residual clay, which is produced during surface weathering of rock by various means and is generally found in the place of origin, (ii) transported clay (or) sedimentary clay, which is produced by the chemical decomposition of rock and could be separated out from the original deposit through erosion... 

Primary Clay or Residual Clay. A clay still remaining in the geographical location where it was formed in the UK such a clay is typified by the china clay (q.v.) of Cornwall (cf. SEDIMENTARY CLAY). 

Most of the domestic supply of residual kaolin is obtained from western North Carohna, and most of the sedimentary clay comes from Georgia, South Carohna and Northern California. The South Carohna kaohns are widely used in the refractory and elastomeric industries. Although some of the South Carohna kaohn deposits have a naturaUy occurring large particle size which makes them excellent casting clays, most... 

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