Silicates framework

Aluminosilicates. These silicates consist of frameworks of silica and alumina tetrahedra linked at all corners to form three-dimensional networks familiar examples are the common rock-forming minerals quartz and feldspar. Framework silicates generally form blocky crystals, more isotropic... 

Framework silicates are also termed tectosilicates. Their common feature is the three-dimensional connection of tetrahedra sharing all four vertices. They are subdivided into ... 

When different Si(nM) sites (n = 0—4) can be resolved in the 29Si solid state NMR spectra of tetrahedral framework silicates, then the Si/M ratio can be determined by the equation [21]... 

Using the flush configuration (Chapter 2), we continuously displace the pore fluid with the flooding solution. In this way, we replace the pore fluid in the system a total of ten times over the course of the simulated flood, which lasts twenty days. Because of the short interval selected for the flood, we assume that the pore fluid does not remain in equilibrium with quartz or framework silicates such as feldspar. 

Feldspar is a framework silicate in which tetrahedra containing A1 or Si are linked to one another by shared oxygens in all directions rather than in chains or sheets (3) The plagioclase solid-solution series... 

Deer, W.A. Howie, R.A. Zussman, J. "Rock-Forming Minerals, Volume 4 - Framework Silicates" Longmans London, 1963. 

Finally, some authigenic clay minerals are produced by the reaction of seawater with fresh volcanic glass. This commonly occurs near mid-ocean ridges and rises or where lava from coastal volcanoes flows into the sea. Clay minerals produced by this process are primarily smectites, such as montmorillonite, and a type of framework silicate called zeolites of which phillipsite and clinoptilite are the most common marine examples. Zeolites are characterized by three-dimensional frameworks with large cavities that... 

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. 

Kieflfer S. W. (1979c). Thermodynamics and lattice vibrations of minerals, 3 Lattice dynamics and an approximation for minerals with application to simple substances and framework silicates. Rev. Geophys. Space Phys., 17 35-59. 

Merlino S. (1976). Framework silicates. Izvj. Jugoslav. Centr. Krist., 11 19-37. 

Examples of these framework silicates include the feldspars, zeolites and ultramarines (see Clays Molecularsieves). 

The Q notation used above is not sufficient to describe the basic building units in a/uminosilicates. While in framework silicates the environment of each silicon atom is always Q4(4Si), in framework aluminosilicates there are five possibilities described by the formula Q4[nAl, (4 — n)Si], where n = 0,1, 2, 3, or 4. We shall for simplicity denote these five basic units as Si(nAl)... 

Higgins and Woessner (106) correlated 29Si chemical shifts in the framework silicates cristobalite, quartz, albite, and natrolite with the mean Si—O bond distances and arrived at the following relationship ... 

The chemical shift anisotropy of the 29Si nucleus is generally small, and thus unlike in l3C solid-state NMR at high fields, no sideband problems are encountered in MAS spectra of framework silicates. 

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