What are tectosilicates in mineralogy ?
Tectosilicates : definition
Numbering about 120 minerals, tectosilicates constitute the major subclass of silicates, alone making up 64% of the earth's crust, thanks in particular to quartz and feldspars, the most abundant of all minerals, feldspathoids, and to zeolites.
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.
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.