1. Cyclosilicates Minerals with rings of tetrahedra T : O ratio = 1 : 3
So the silicate group is
n(SiO3), where n=3,4 or 6

2. The cyclosilicates may contain three-, four- or six-membered rings of SiO4 tetrahera:
Three-membered rings are exemplified by benitoite BaTiSi3O9
Four-membered rings are exemplified by axinite (Ca,Fe,Mn)3Al2BO3(Si4O12(OH) in which the silicate rings alternate with BO3 rings.

3. Six-membered rings are more common and are seen in:
Tourmaline has the general formula WX3Y6(BO3)3(Si6O18)(OH,F)4 giving rise to a number of different compositions; i.e. individual species. A typical formula is (Na,Ca)(Fe,Mg,Al,Li)3Al6(BO3)3Si6O18(OH) in which BO3 rings alternate with the silicate rings.

4. Tourmaline

5. Tourmaline Al, Fe3+,Mn3+ BO3 triangle
Yellow- OH and Ca, Na – blue, Li, Mg, Al - black
BO3 triangle

6. Beryl Be3Al2Si6O18 and cordierite Mg2Al4Si5O18 are considered by some to be framework silicates, but the silicate rings are the main structural feature.

7. Beryl
Be3Al2Si6O18

8. Purple – Be, green - Al

9. Cordierite

10. Cordierite (Mg, Fe)2[Al4Si5O18], orthorhombic, Cccm
6-member silica rings linked to adjacent rings those above and below by octahedrally-coordinated Mg, Fe3+ and Al. Blue dots represent sites for possible alkali metals or H2O

11. Some texts cite the mineral ekanite as an example of an eight- membered ring structure. However, it is composed of two four-membered rings linked by their apical oxygens. Thus, three corners of each tetrahedron are shared and the Si:O ratio is 2:5, in violation of the definition of ring silicates. This is another example of the weakness of the traditional definition of the silicate sub-classes.
ThK(Ca,Na)2Si8O20