Silicates Tecto

Three-dimensional or tecto-silicates Three-dimensional frameworks of [Si04] tetrahedra sharing all four oxygen atoms Feldspars, zeolites, ultramarines... 

R.M. Barrer, Isomorphous Replacements in the Framework of Zeolites and Other Tecto-silicates, in Hydrothermal Chemistry of Zeolites, Academic Press London, 1982, 251-305. 

The outermost layer of our planet, the crust, contains the accessible mineral wealth of the planet. The eight most abundant elements in the crust (Table 1) make up 98.5% of the mass of the crust [10], The most common metal, silicon, is never found in its elemental form in nature. Instead, silicon is combined in silicate minerals, which make up more than 90% of the mass of the Earth s crust [11], Depending on the composition and formation conditions, silicate minerals have structures that range from individual clusters (orthosilicates) to three-dimensional networks (tecto-silicates) [11], These minerals can be contained in relatively pure single mineral deposits or, more commonly, in rocks such as granite that are made up of one or more mineral species. 

Langasite is a kind of materials with framework structure without inversion symmetry i. quartz and BeO are also framework structure which is formed mainly by a covalent bond such as Si04, AIO4, Zn04. Especially, silicates including lanj ite make many framework structures by connection of Si04 tetrahedra as cydo-, ino-, phyllo-, and tecto-silicates. These framework structures are noticed recently for appHcations on many kinds of properties such as zeolite for optical properties by absorption of special compwimds. 

Subclasses also exist and the most useful ones are probably the neso-, soro-, cyclo-, ino-, phyllo-, and tecto-silicates which give some indication of the state of polymerization of SiOt tetrahedra into rings, chains, bands, sheets, networks, and so forth. 

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