what are pyrosilicates and cyclicsilicates?
Pyrosilicates are silicates which contain Si2O76-. They are formed by joining two tetrahedral Si2O44-. When two Si2O44- are joined, there is removal of one oxygen atom and the two units join at the corner oxygen atom. Example is thortveitite, Sc2Si2O7. The structure of pyrosilicate is:
The reds are oxygen atoms and greens are silicon.
Cyclic silicates contains (SiO3)n2n- which are formed by linking three or more tetrahedral SiO44- units cyclically. Each SiO44- shares two oxygen atoms with other unit. Example is Benitoite, BaTi(SiO3)3. Here three SiO44- units are arranged cyclically.
Structure of a cyclic silicate:
