Minerals in clay

Shirozu, H. (1969) Chlorite minerals. In Clay of Japan. Tokyo Japan Geol. Survey, pp. 64-67. 

The silicates are divided into five subgroups, which differ in the structures of their silicate anions. Each silicate anion consists of one or more Si04 tetrahedrons which are linked in various ways. This group of substances is discussed more elaborately than the other ones because these minerals are most abundant in the lithosphere and because the clay minerals in clay also belong to the silicates. 

Some silicate minerals are also formed in a similar manner. The process is very slow, slower than even carbonate formation, because of the very low solubility of silicate minerals. In clay minerals, or in lateritic soils, silicates dissolve very slowly to form an intermediate product, silicic acid (H4Si04), which subsequently will react with other sparsely soluble compounds and form silicate bonding phases. Thus, a dissolution-precipitation process seems to be crucial to forming some silicate minerals. 

Over 150,000 unique powder diffraction data sets have been collected from organic, organometallic, inorganic and mineral samples. These have been compiled into a database known as the JCPDS (Joint Committee on Powder Diffraction Standards). The experimental diffraction data can be cross-matched by on-line search or by comparing the three most intense reflections. This methodology is used as a quick method for the identification of impure materials, and it is also used widely in industry, e.g. for quality control in drug samples or the partition of minerals in clays. 

Cement is made from a mix ture of limestone and clay. The most important minerals in clay are the combinations of aluminum, oxygen, and silicon known as aluminum silicates. 

P.F. Kerr, Formation and occurrence of clay minerals, in Clays and Clay Technology, Proceedings of the First National Conference on Clays and Clay Technology, J.A. Pask and M.D. Turner (eds.), California Division of Mines, San Francisco, 1955, pp. 19-32. 

Biogenic activity. In sandy soils, rapid microbial decomposition of organic matter is facilitated up to its mineralization. In clay soils, anaerobic processes are prevalent with humic substances occurring as decomposition products, and under extremely anaerobic conditions, insufficiently decomposed organic matter may be accumulated. 

Illites often occur as an accessory mineral in clays, to the extent of 40% or more. 

H. Heystek [1954] has summarized his investigations of mixed-layer minerals in clays and shales of South African origin. He mentions an illite from Gollel, Swaziland (10.26 A 001 reflection), and two mixed-layer clays, from Addo and Albertina (Bokkeveld Series, C.P.). 

The quantitative determination of minerals in clays. Univ. Carol. Geol. Suppl. 

Kodama, H., and K. Oinuma, 1962. Identification of kaolin minerals in clays by X-ray and infrared absorption spectra. Clay Sci. 1 113. 

Washing and dewatering by air displacement of cakes are possible. AppHcations are in the treatment of minerals, in the sugar industry, and in the treatment of municipal sewage sludge and fillers like talc, clay, whiting, etc. 

Table 6. Rare-Earth Oxide Distribution in Mineral and Clay Sources, wt ...

The multitude of variation in clay minerals is caused by substitution in the octahedral and tetrahedral layers resulting in charge deficits. The manner in which the charge deficit is balanced leads to many of the useful and unique properties of clay minerals. 

Talc and Pyrophyllite. Talc (qv) and pyrophjlhte are 2 1 layer clay minerals having no substitution in either the tetrahedral or octahedral layer. These are electrostatically neutral particles (x = 0) and may be considered ideal 2 1 layer hydrous phyUosiHcates. The stmctural formula of talc, the trioctahedral form, is Mg3Si402Q(0H)2 and the stmctural formula of pyrophylUte, the dioctahedral form, is Al2Si402Q (OH)2 (106). Ferripyrophyllite has the same stmcture as pyrophylUte, but has ferric iron instead of aluminum in the octahedral layer. Because these are electrostatically neutral they do not contain interlayer materials. These minerals are important in clay mineralogy because they can be thought of as pure 2 1 layer minerals (106). 

Palygorskite and sepioHte are different from other clay minerals in the manner in which the 2 1 layers are joined. Rather than being joined in a continuous manner, the tetrahedral sheets are joined to an adjacent inverted tetrahedral layer, making the octahedral layers noncontinuous and leaving an open channel in the mineral stmcture (37,38,148). The dimension of palygorskite is teI.S nm (18 E) the dimension of sepioHte is 9e2.7 nm (27 E) (37). 

An alternative description of iUite—smectite mixed-layer clays begins with megacrystals of smectite that incorporate smaller packets of iUite (163). These constituents are observed as mixed-layer minerals in x-ray analysis. Diagenesis increases the percentage of iUite layer and with increasing alteration the mixed-layer mineral takes on the characteristics of an iUite dominated iUite—smectite. 

B. Velde, Clcys and Clay Minerals In Natural and Synthetic Systems, Elsevier, New York, 1977. 

In the production of ceramic ware the shape of the ware must be retained after drying and the ware must be free from cracks and other defects. Controlled drying helps to minimize defects. In general, clays containing moderate amounts of nonclay minerals are easier to dry than those composed whoUy of clay minerals. Furthermore, clays composed of iUite, chlorite, and kaolinite are relatively easier to dry than those composed of montmorillonite. 

When the ore contains a large amount of clay minerals, these form difficult to separate slimes, which hinder the recovery of the minerals (see Clays). The tailing from the scavenger cells can be cycloned to remove the slimes before the coarse material is floated in a tailings retreatment plant. The flotation product from the rougher cells of this plant can be reground and cleaned. This additional treatment of the tailings from the main copper flotation plant may improve the recovery of metal values by 1—3%. 

Variations in interlayer cation sites in clay minerals as studied by Cs MAS nuclear magnetic resonance spectroscopy. Am. Mineral. 75 970 (1990). ... 

Ceramics and minerals present many common problems, but ceramics warrant special treatment because elements of low atomic number predominate in them and they consequently offer x-ray emission spectrog-raphy of the light elements an excellent opportunity to prove its usefulness. Scott,8 in making this clear, emphasized the absorption and enhancement effects to be expected, and pointed out the need for careful sample preparation. By use of a General Electric XRD-5 spectrograph and associated equipment, he set up working curves for alumina, silica, potash, lime, phosphate, titania, and iron oxide in clays, refractories, and other ceramic materials. 

Discuss the significance of clay minerals in a description of the solid phase of a sediment. 

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