What are tectosilicates in mineralogy ?
Tectosilicates : definition
In the structure of tectosilicates, the SiO4 tetrahedra are all linked by their 4 vertices, thus building a three-dimensional network with the structural formula SiO2.
However, apart from the silica group, the SiO4 tetrahedra of tectosilicates undergo significant substitutions of Si by Al (up to 50%), which is why they are called aluminosilicates. The replacements of Si4+ by Al3+ lead to electrical imbalances which must be neutralized by the integration of metal ions (Na+, K+, Ca2+, etc...) in the cavities of the crystalline structure, allowing the crystallization of feldspars, feldspathoids, etc... and giving its chemical diversity to this subclass.