Cyclosilicates
The cyclosilicates form rings of linked [SiO4]4- tedrahedra with either [Si3O9]6-,
[Si4O12]8-, or [Si6O18]12- configurations. Cordierite with the
chemical formula (Mg,Fe)2Al4Si5O18 represents an example of the cyclosilicate group.
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Inosilicates
In the inosilicates, [SiO4]4- tedrahedra are linked as chains, which in turn are linked together by cations.
Single-chain inosilicates form [Si2O6]4- groups, and double-chain inosilicates
form [Si4O11]6- groups. Pyroxenes, e.g. diopside with the chemical formula
CaMgSi2O6, are single-chain, and amphiboles, e.g. hornblende
(Ca2(Mg,Fe,Al)5(Al,Si)8O22(OH)) or actinolite
(Ca2(Fe,Mg)5Si8O22(OH)2) are double-chain inosilicates.
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Nesosilicates
In the nesosilicate group, [SiO4]4- tedrahedra are isolated from each other and share their oxygens
with octahedral groups, which contain cations, such as Mg2+, Fe2+, or Ca2+. A common
rock-forming mineral of the nesosilicate group is
olivine with the chemical formula
(Mg,Fe)2SiO4.
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Phyllosilicates
Phyllosilicates comprise sheets of [SiO4]4- tedrahedra rings, where three of the four oxygens of
each tedrahedrons are shared resulting in [Si4O10]4- groups. Biotite with the
chemical formula K(Mg,Fe)3(AlSi3O10)(F,OH)2 is a common rock-forming phyllosilicate.
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Sorosilicates
Two [SiO4]4- tedrahedra are linked by a shared corner oxygen to form
[Si2O7]6- groups. An example for the sorosilicate group is the mineral epidote with the
chemical formula Ca2Al2(Fe3+,Al)(SiO4)(Si2O7)O(OH).
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Tectosilicates
Complete linkage of [SiO4]4- tedrahedra results in the 3-dimensional framework of the tectosilicates.
Quartz (SiO2) and the feldspars
(plagioclase,
microcline)
(e.g. anorthite, CaAl2Si2O8) are tectosilicates.
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