SiO4tetraedriä

SiO4 tetrahedra, also known as orthosilicate tetrahedra, are fundamental structural units in many silicate minerals. Each tetrahedron consists of a central silicon atom covalently bonded to four oxygen atoms. These oxygen atoms are positioned at the vertices of a regular tetrahedron, with the silicon atom at its center. The chemical formula for a single, isolated SiO4 tetrahedron is Si4+O4.

In minerals, these tetrahedra can exist as discrete, isolated units, as seen in nesosilicates like olivine. Alternatively, they can link together by sharing oxygen atoms to form more complex structures. This sharing can occur at one, two, three, or all four corners, leading to the formation of chains, rings, sheets, and three-dimensional frameworks. This polymerization is responsible for the vast diversity of silicate mineral structures. The silicon atom carries a +4 charge, and each oxygen atom carries a -2 charge, resulting in a net charge of -4 for the isolated tetrahedron. This negative charge is balanced by cations in the mineral structure. The arrangement of these tetrahedra and the associated cations dictates the physical and chemical properties of silicate minerals.