frameworksilicate

Framework silicates, also known as tectosilicates, are defined by a three-dimensional framework built from SiO4 tetrahedra in which each tetrahedron shares all four oxygen atoms with adjacent tetrahedra. This complete polymerization produces a rigid, extended Si–O network that runs throughout the mineral structure.

In many framework silicates aluminum can substitute for silicon in the framework. Because aluminum introduces a lower positive charge, such substitutions impart a net negative framework charge that must be balanced by extra-framework cations such as Na+, K+, Ca2+, or by protons. The distribution of these charge-balancing species influences the mineral’s properties and stability.

Common members include quartz (SiO2), which contains a pure silica framework; feldspars, comprising potassium feldspar, plagioclase series (sodium and calcium varieties), and other related compositions; and zeolites, aluminosilicate frameworks with pore spaces that often host water and exchangeable cations. These examples illustrate the structural diversity within framework silicates, from the simple, highly stable quartz to the more complex, ion-exchange-capable zeolites.

Framework silicates dominate the Earth’s crust, especially feldspars and quartz. They have broad industrial relevance: quartz contributes to hardness and thermal stability in glass and ceramics; feldspars are major glass and ceramic raw materials; zeolites are valued for adsorption, ion exchange, and catalytic applications.