tectosilicate

Tectosilicate, or framework silicate, is a class of silicate minerals in which the silicon-oxygen tetrahedra (SiO4) share all four oxygen atoms with neighboring tetrahedra, forming a three-dimensional framework. This complete corner-sharing links the tetrahedra into an extensive, highly polymerized network that is structurally robust. In many tectosilicates, some silicon is replaced by aluminum, creating a framework with a negative charge that is balanced by interstitial cations such as Na+, K+, or Ca2+.

Common tectosilicates include quartz (SiO2) and the feldspars, which comprise alkali feldspars (orthoclase, microcline) and the plagioclase series (albite to anorthite). The class also contains framework aluminosilicates such as zeolites, which have channels and cavities that host water molecules and cations. Quartz is purely silicon-oxygen, whereas feldspars incorporate aluminum into the framework, affecting symmetry, cleavage, and stability.

Tectosilicates are among the most abundant mineral families in the Earth's crust. Quartz is a widespread accessory and framework mineral, while feldspars constitute a major component of many igneous rocks and overall crustal material. The framework linkage in these minerals underpins their physical properties, including hardness (quartz), general cleavage patterns in feldspars, and their response to weathering and crystallization conditions. In classification terms, tectosilicates represent the highest degree of silicate polymerization, more connected than inosilicates, phyllosilicates, or other silicate groups.