Silicates classification

Nesosilicates are the simplest silicates. They contain isolated or independent Si04 tetrahedra. This group has also been called the orthosilicates. A secondary classification, the nesosubsilicates has been designated by Strunz (1957), who was the originator of the silicate classification. This subclass included species having a second anion or anionic radical. The nesosilicates include the gem minerals zircon, topaz, and the garnet and olivine groups. 

Uses Crosslinking agent in vulcanization of natural rubber, S/B copolymer, acrylonitrile-butadiene copolymer, ethylene-propylene terpolymers for food-contact articles for repeated use accelerator for food-contact rubber articles for repeated use Regulatory FDA 21CFR 177.2600 Diisostearoyl trimethylolpropane siloxy silicate Classification Silicone polymer... 

Liebau, F. (1982). Principles of Silicate Classification Based on Crystal Chemistry. Sov.Phys.Crystallogr. 27,66 - 72. 

Silicates are materials composed primarily of silicon and oxygen, the two most abundant elements in Earth s crust consequently, the bulk of soils, rocks, clays, and sand come under the silicate classification. Rather than characterizing the crystal structures of these materials in terms of unit eeUs, it is more convenient to use various arrangements of an SiOl tetrahedron (Figine 12.9). Eaeh atom of silicon is bonded to four oxygen atoms. 

Certain treatment systems fall in the category of cement-pozzolanic processes and have been in use for some time outside the U.S. In these systems, both cement and lime-siliceous materials are used in combination to give the best and most economical containment for the specific waste being treated In general, the bulk of the comments (under both classifications above) hold for techniques using a combination of treatment materials. 

A. Determination of silica in a soluble silicate Discussion. Most of the silicates which come within the classification of soluble silicates are the orthosilicates formed from SiO units in combination with just one or two cations. More highly condensed silicate structures give rise to the insoluble silicates. 

The Lux-Flood theory relates to oxide melts. Geologists have often used acid-base concepts for the empirical classification of igneous silicate rocks (Read, 1948). Silica is implicitly assumed to be responsible for acidity, and the silica content of a rock is used as a measure of its acid-base balance ... 

In order to study in more detail the clay minerals, it is first helpful to review briefly the basic structural classification of the silicates in general. Although ultimately complicated, the general progression is logical, and is based on the degree of polymerization of the basic structural unit which is the Si04 tetrahedron (see below). The sequence runs as follows ... 

Table 4.2 summarizes this basic classification and terminology of silicates. It is worth remembering that the term infinite refers here to an atomic scale of measurement, and does not imply that the chains extend to infinity in the mathematical sense of the word The terminology surrounding the silicates and clay minerals, in common with other mineralogical terms, has never been fully systematized, and so the names given are often ill-defined, or not unique to a... 

Figure 8. Figure (a) after Clayton et al. (1976, 1977). The scales are as in Figure 1. The O isotopic compositions of the different meteorite classes are represented ordinary chondrites (H, L, LL), enstatite chondrites (EFl, EL), differentiated meteorites (eucrites, lAB irons, SNCs) and some components of the carbonaceous chondrites. As the different areas do not overlap, a classification of the meteorites can be drawn based on O isotopes. Cr (b) and Mo (c) isotope compositions obtained by stepwise dissolution of the Cl carbonaceous chondrite Orgueil (Rotaru et al. 1992 Dauphas et al. 2002), are plotted as deviations relative to the terrestrial composition in 8 units. Isotopes are labeled according to their primary nucleosynthetic sources. ExpSi is for explosive Si burning and n-eq is for neutron-rich nuclear statistical equilibrium. The open squares represent a HNOj 4 N leachate at room temperature. The filled square correspond to the dissolution of the main silicate phase in a HCl-EIF mix. The M pattern for Mo in the silicates is similar to the s-process component found in micron-size SiC presolar grains as shown in Figure 7.

Each of these solid phases can be described in terms of their mineralogy. This classification scheme is based on crystal structure and chemical composition. The most common minerals found in marine sediments are listed in Table 13.2. Most are silicates in which Si and O form a repeating tetrahedral base unit. Other minerals common to marine sediments are carbonates, sulfates, and oxyhydroxides. Less common are the hydrogenous minerals as they form only in restricted settings. These include the evap-orite minerals (halides, borates, and sulfates), hydrothermal minerals (sulfides, oxides, and native elements, such as gold), and phosphorites. 

Smith, J.V. and Bennett, J.M. (1981) Enumeration of 4-connected 3-dimensional nets and classification of framework silicates the infinite set of ABC-6 nets the Archimedean and. sigma.-related nets. Am. Mineral., 66 (7-8), 777-788. 

Smith, J.V. (1977) Enumeration of 4-connected 3-dimensional nets and classification of framework silicates. 

The chemical classification of silicates is based on their multiplicity and type of structural arrangement. It partly differs from the classification commonly adopted in mineralogy (table 5.2). 

Table 5.3 Rostov s classification of silicates. A = axial P planar I = isometric (from Liebau, 1982).

Pyroxenes are poly silicates ( inosilicates in the mineralogical classification), crystallizing, respectively, in the monoclinic clinopyroxenes spatial groups C2lc, Pljlc, P2ln) and orthorhombic systems orthopyroxenes spatial groups... 

Kostov I. (1975). Crystal chemistry and classification of silicate minerals. Geochem. Mineral Petrol, 1 5-14. 

Liebau E (1982). Classification of silicates. In Reviews in Mineralogy, vol. 5, P. H. Ribbe (series ed.), Mineralogical Society of America. 

The following list is a presentation of all minerals, mineral series, and mineral groups described in standard mineralogy texts and references as occurring in fibrous, acicular, or needlelike forms. The presentation follows the outline given in The System of Mineralogy of J. D. Dana and E. S. Dana (7th ed. Palache, Berman, and Frondel, eds.). The silicates and aluminosilicates follow the classifications of Rock Forming Minerals (Deer, Howie, and Zussman, eds.). 

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