Silikaattiryhmiä

Silikaattiryhmiä refers to silicate groups, which are fundamental building blocks in the chemistry and mineralogy of silicates. Silicates are a large and diverse class of compounds, making up a significant portion of the Earth's crust. They are characterized by the presence of silicon and oxygen atoms. The basic unit of all silicates is the silicon-oxygen tetrahedron, often represented as SiO4^4-. In this structure, a single silicon atom is covalently bonded to four oxygen atoms, forming a tetrahedral shape.

The way these tetrahedra are linked together determines the classification of silicate minerals into different groups. These groups are defined by the degree of polymerization of the SiO4 tetrahedra. The simplest group is the nesosilicates, where individual SiO4 tetrahedra are isolated and held together by interstitial cations. Examples include olivine and garnet.

Next are the sorosilicates, where two tetrahedra share a single oxygen atom, forming a Si2O7^6- group. Epidote is a common sorosilicate. The cyclosilicates feature rings of tetrahedra, such as the Si3O9^6-, Si4O12^8-, and Si6O18^12- groups, found in minerals like beryl and tourmaline.

The inosilicates are characterized by chains of tetrahedra. Single-chain inosilicates, or pyroxenes, have a repeating unit of SiO3^2-. Double-chain inosilicates, or amphiboles, have a repeating unit of Si4O11^6-. Phyllosilicates, or layer silicates, have tetrahedra arranged in sheets, with a repeating unit of Si2O5^2-. Micas and clay minerals belong to this group. Finally, the tectosilicates, also known as framework silicates, have a three-dimensional framework where each tetrahedron shares all four of its oxygen atoms with neighboring tetrahedra, resulting in a Si1O2 structure. Quartz, feldspars, and zeolites are examples of tectosilicates. The classification into these silicate groups is crucial for understanding the properties and occurrence of silicate minerals.