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The Silicate Minerals

Most of the minerals that constitute rocks and soil are silicates, which usually also contain aluminum. Many of these minerals have complex formulas, corresponding to the complex condensed silicic acids from which they are derived. These minerals can be divided into three principal classes the framework minerals, with three-dimensional covalent bonding (hard minerals similar in their properties to quartz), the layer minerals, with two-dimensional bonding (such as mica), and the fibrous minerals, with one-dimensional bonding (such as asbestos). [Pg.610]

A characteristic feature of these tetrahedral framework minerals is that the number of oxygen atoms is just twice the sum of the number of aluminum and silicon atoms. In some of these minerals the framework is an open one, through which corridors run that are sufficiently large to permit ions to move in and out. The zeolite minerals, used for softening water, are of this nature. As the hard water, containing Ca++ and Fe ions, passes around the grains of the mineral, these cations enter the mineral, replacing an equivalent number of sodium ions. [Pg.610]

Some of the important minerals in soil are aluminosilicate minerals that have the property of base exchange, and that, because of this property, serve a useful function in the nutrition of the plant. [Pg.610]

A portion of an infinite layer of silicate tetrahedra, as present in talc and other minerals with layer structures. [Pg.611]

18 / Lithium, Beryllium, Boron, and Silicon and Their Congeners [Pg.612]


C. E. Marshall, The Colloid Chemistry of the Silicate Minerals, Academic Press, Inc., New York, 1949. [Pg.201]

Closely related to silica are the silicate minerals, all of which contain polyatomic anions made of silicon and oxygen. The simplest silicates, called orthosilicates, contain Si04 anions. The 8104 anion is tetrahedral, with a central silicon atom bonded to four outer oxygen atoms. [Pg.613]

An extension of the reduction-chlorination technique described so far, wherein reduction and chlorination occur simultaneously, is a process in which the oxide is first reduced and then chlorinated. This technique is particularly useful for chlorinating minerals which contain silica. The chlorination of silica (Si02) by chlorine, in the presence of carbon, occurs above about 1200 °C. However, the silica present in the silicate minerals readily undergoes chlorination at 800 °C. This reaction is undesirable because large amounts of chlorine are wasted to remove silica as silicon tetrachloride. Silica is, therefore, removed by other methods, as described below, before chlorination. Zircon, a typical silicate mineral, is heated with carbon in an electric furnace to form crude zirconium carbide or carbonitride. During this treatment, the silicon in the mineral escapes as the volatile oxide, silicon monoxide. This vapor, on contact with air, oxidizes to silica, which collects as a fine powder in the furnace off-gas handling system ... [Pg.403]

Mixtures of iron and stone principally as the silicate mineral olivine, (Mg,Fe)2Si04, with additional Fe and Ni... [Pg.163]

Section 4.3 sets out the principles underlying the structure of the silicate mineral family. Natural clay deposits are formed by the chemical weathering of rocks -largely as a result of the attack by slightly acidic surface waters. Rainwater,... [Pg.119]

There are no unequivocal weathering reactions for the silicate minerals. Depending on the nature of parent rocks and hydraulic regimes, various secondary minerals like gibbsite, kaolinite, smectites, and illites are formed as reaction products. Some important dissolution processes of silicates are given, for example, by the following reactions ... [Pg.158]

Based on the study of expanding clay minerals, two models of water adsorbed on silicate surfaces have been proposed. One states that only a few layers (<5) of water are perturbed by the silicate surface, the other concludes that many layers (perhaps 10 times that number) are involved. The complexity of the interactions which occur between water molecules, surface adsorbed ions, and the atoms of the silicate mineral make it very difficult to unequivocally determine which is the correct view. Both models agree that the first few water layers are most perturbed, yet neither has presented a clear picture of the structure of the adsorbed water, nor is much known about the bonding of the water molecules to the silicate surface and to each other. [Pg.51]

Present M sbauer Studies of Natural Pyroxenes and Olivines. Table IX gives the major element chemical compositions of the silicate minerals examined in this study. Table X compares the Mossbauer parameters of these minerals, while Figures 9-13 show representative Mossbauer spectra. Fayalite (Figure 9) is the only olivine in this group. The two lines are, however, somewhat broadened (0.35 and 0.39 mm./ sec.) compared with the width of natural iron foil lines observed with our source (0.24 mm./sec.) and suggest the near coincidence of two quadrupole-split doublets resulting from Mi and M2 sites. Analysis of this "two-line spectrum into a four-line spectrum in the manner described by Evans et al (11) could possibly yield parameters for the two iron sites, but this was not undertaken since both lines appear symmetric. The "two-line quadrupole splitting of 2.78 mm./sec. is somewhat smaller... [Pg.75]

Here the principles of constructing a 3D structure model from several HREM images of projections of inorganic crystals will be presented. Some of the principles may also be applied to non-periodic objects. A complex quasicrystal approximant v-AlCrFe is used as an example (Zou et al., 2003). Procedures for ab initio structure determination by 3D reconstruction are described in detail. The software CRISP, ELD. Triple and 3D-Map are used for 3D reconstruction. The 3D reconstruction method was demonstrated on the silicate mineral (Wenk et al. 1992). It was also applied to solve the 3D structures of a series mesoporous materials (Keneda etal. 2002). [Pg.305]

Biogeochemists use the terms dissolved silica (DSi) or dissolved silicate to collectively refer to all of the dissolved silicon. Silicic acid exhibits tetrahedral geometry with the silicon atom at the center and a hydroxyl group occupying each of the four corners. This structure is similar that of the mineral silicate tetrahedra (Figure 14.3c). Chemical weathering of the silicate minerals is the major source of DSi to the ocean, giving rise to the term dissolved silicate, which is usually abbreviated to just silicate. ... [Pg.404]

This is a very sketchy depiction of the deep carbon cycle because it illustrates only the behaviors of calcium and silica. In reality, a wide variety of other cations are present in the silicate minerals, such as in the plagioclase feldspars (Table 13.2). Furthermore, not all of the limestone is converted into siUcate minerals some remains as limestone. Uplift of the limestone onto land, followed by chemical and biological weathering, is another sink for atmospheric CO2, via... [Pg.713]

Properties and reactions of individual chemical substances for example, the silicate minerals. [Pg.1]

Some of the diversity that characterizes the properties and compositions of the silicate minerals stems from the ability of the aluminum ion (Al ) to substitute for silicon in the tetrahedral unit. When silicate tetrahedra in a mineral are replaced by aluminum-containing tetrahedra, concomitant changes occur in the size of the tetrahedron (usual Si—O bond length = 0.160 nm. A1—O bond length = 0.178 nm) and in the cations or protons that balance the tetrahedral unit charge. Regular substitutions with distinct chemistries and structures lead to the formation of groups of discrete minerals called aluminosilicates. [Pg.23]

Much of the literature published on minerals is based on high rank coals, but can be related to low rank coals (18). In general, the silicate minerals represent the major component of the minerals contained in coal. The most common analytical methods for mineral characterisation and analysis are listed in (19) and covered in detail in the "Analytical Methods for Coal and Coal Products" series (20). [Pg.21]

Reference Minerals. The 42 reference minerals and the mineral classes used are listed in Table II. Most of the minerals were obtained from Ward s Natural Science Establishment, Inc., Rochester, New York. Many of the silicate minerals were American Petroleum Institute (API) standard samples or their equivalents. Numbers given in the table (e.g., kaolinite 4) refer to the API standard designation. When available, several minerals of each type were... [Pg.45]

Lithium.—In order to extract lithium from the silicate minerals—petalite, lepidolite, spodumene, amblygonite, etc.—J. J. Berzelius 3 fused the finely powdered mineral with twice its weight of calcium or barium carbonate. L. Troost fused a mixture of finely powdered lepidolite with an equal weight of barium carbonate, half its weight of barium sulphate, and one-third its weight of potassium sulphate. In the latter case, two layers were formed lithium and potassium sulphates accumulated in the upper layer from which they were extracted by simple lixiviation. The sulphates are converted to chlorides by treatment with barium chloride. The filtered liquid is evaporated to dryness, and the chlorides extracted with a mixture of absolute alcohol, or pyridine. The lithium chloride dissolves, the other alkali chlorides remain as an almost insoluble residue. [Pg.443]

The differentiation between cations and anions in regard to size and charge is reflected in the rules markedly different roles are attributed to cations and anions in a crystal. The rules are based upon the concept of the coordination of anions at the corners of a tetrahedron, octahedron, or other polyhedron about each cation, as assumed in the early work of W. L. Bragg on the silicate minerals, and they relate to the nature and interrelations of these polyhedra. [Pg.544]

This simple rule restricts greatly the acceptable structures for a substance, and it has been found useful in the determination of the structures of complex ionic crystals, including especially the silicate minerals. The rule is satisfied nearly completely by most, of the structures that have been reported for the silicate minerals, deviations by as much as i being rare. Somewhat larger deviations from the rule are occasionally found for substances prepared in the laboratory, for which stability as great as for minerals is not expected. [Pg.549]

The lithophile elements are those that generally occur in silicate phases and include among others Si, Al, Ti, K, Na, Zr, Be, and Y. These would be expected to occur in coals in some combination with the silicate minerals kaolinite, illite, other clay minerals, quartz, and stable heavy detrital minerals. [Pg.18]

Taking into consideration die stability of structures involving C-Si bonds, it is evident that the basic chain itself must be comparable in its stability to that of silica and the silicate minerals, and if the R substituents contain no carbon-to-earbon bonds, as for example with methyl groups, the combination should have excellent thermal stability and chemical resistance. [Pg.1480]

A rich variety of crystal structures are made possible by hydrogen bonding. The variety is comparable to that found amongst the silicate minerals, and it is similarly based on a limited number of simple structural themes. We illustrate a few of the pattern-types revealed by crystal-structure analysis. [Pg.31]


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