This can be balanced in a number of ways. For example the oxygen ion can be shared by two adjacent tetrahedra, in which case the net charge is zero. Then no further balancing is necessary. If, on the other hand, the oxygen is not shared, the negative charge will be balanced by a metal ion, for example by Iron, Calcium or Magnesium.

Because these metal ions are large they are not adequately "shielded" by the Oxygen and therefore need six instead of four oxygen ions. The metal thus sits in the middle of an octahedron. This combination of tetrahedra and octahedra, coupled with the large number of diffrenet metal ions, gives rise to an almost infinite variety and complexity of structures. These are reflected in the many families of Silicate minerals.

Nesosilicates:

The nesosilicates are characterized by isolated silicate tetrahedra that are bound to each other only by positively charged elements.

Sorosilicate:

The sorosilicates are characterized by isolated double silicate tetrahedra that share an oxygen.

Cyclosilicate:

The cyclosilicates are characterized by rings of linked silicate tetrahedra.

Inosilicates:

The inosilicates are characterized by single or double chains of linked silicate tetrahedra.
Many similarities exist between the two groups. The only readily distinguishing feature between the minerals is that minerals of the single chain inosilicates have 90° cleavage while the minerals of the double chain inosilicates have 60° cleavage.

Phyllosilicates:

The Phyllosilicates are characterized by sheets of linked silicate tetrahedra. The term phyllon comes from the Greek meaning "leaf." This is because all of the members of this class of silicates have platy or flaky habit and one prominent cleavage. The minerals are generally soft, of relative low specific gravity and may even have a greasy feel. Cleaved samples show flexibility or even elasticity if the sheets are thin enough.

The minerals of this class are the products of rock weathering and are important in soils. They control the release of minerals into the soil for plant growth and help maintain soil moisture. They also help the soil interact with atmospheric gases and allow burrowing organisms to pass through.

Tectosilicates:

Nearly 75% of the Earth's crust is made up of minerals of the tectosilicate class. The silicate structures of this class are characterized by a very strong and stable three-dimensional framework.