SiO4tetraedreillä

The SiO4 tetrahedron, also known as the orthosilicate tetrahedron, is the fundamental structural unit of many silicate minerals. It consists of a central silicon atom covalently bonded to four oxygen atoms. These oxygen atoms are arranged at the corners of a regular tetrahedron, with the silicon atom at the center. The silicon atom has a charge of +4, and each oxygen atom has a charge of -2, resulting in an overall charge of -4 for the isolated SiO4 tetrahedron ([SiO4]4-).

In silicate minerals, these tetrahedra rarely exist in isolation. Instead, they link together by sharing oxygen atoms. The way these tetrahedra connect dictates the structure and properties of the resulting mineral. Common polymerization arrangements include:

Nesosilicates (or orthosilicates) feature isolated SiO4 tetrahedra, with cations balancing the negative charge.

Sorosilicates (or disilicates) involve two tetrahedra sharing one oxygen atom.

Inosilicates (or chain silicates) have tetrahedra linked in single chains (pyroxenes) or double chains (amphiboles).

Cyclosilicates (or ring silicates) form rings of tetrahedra.

Phyllosilicates (or sheet silicates) arrange tetrahedra into two-dimensional sheets.

Tectosilicates (or framework silicates) form three-dimensional networks where all four oxygen atoms of each tetrahedron are shared.

The strength of the Si-O bond is significant, making the tetrahedron a very stable unit. The arrangement and bonding of these SiO4 tetrahedra are crucial for understanding mineral classification, physical properties like hardness and cleavage, and geological processes.