Cyclosilicaten

Cyclosilicaten are a group of silicate minerals characterized by their fundamental structural unit, the silicon-oxygen ring. In these structures, discrete SiO4 tetrahedra are linked together by sharing oxygen atoms at their vertices, forming closed rings. The most common cyclosilicates feature rings composed of three, four, or six tetrahedra. These rings are typically arranged in layers and are further bonded by interstitial cations, such as magnesium, iron, lithium, or beryllium. The size and charge of these cations influence the specific crystal structure and properties of the cyclosilicate.

The simplest and most abundant cyclosilicates are the six-membered rings. Minerals like tourmaline, which contains a complex structure with borate and aluminum polyhedra in addition to silicon-oxygen rings, are well-known examples. Beryl, another important cyclosilicate, is known for its gemstone varieties like emerald and aquamarine, and it also features six-membered rings. Other cyclosilicates include dioptase with its striking emerald-green color, and axinite, a group of minerals with distinct crystal habits. The specific arrangement of these rings and the interstitial cations determine the mineral's physical properties, including its hardness, cleavage, and optical characteristics. Cyclosilicates are found in a variety of geological environments, from igneous and metamorphic rocks to pegmatites and hydrothermal veins.