silikaatrühma

Silikaatrühma is a term used in geology to describe silicate minerals that share a common structural characteristic: the presence of discrete SiO4 (silicon-oxygen) tetrahedra. These tetrahedra are the fundamental building blocks of all silicate minerals, but in the silikaatrühma, they are not linked together into larger structures like rings, chains, or sheets. Instead, each silicon-oxygen tetrahedron is isolated and bonded to neighboring metal cations. This isolated structural unit gives the silikaatrühma their unique properties.

Examples of minerals belonging to the silikaatrühma include olivine, garnet, and perovskite. Olivine, a common mineral in the Earth's mantle, is a solid solution series with the general formula (Mg,Fe)2SiO4. Garnets are a group of silicate minerals with a complex but consistent structure that allows for a wide range of chemical substitutions, often expressed as X3Y2(SiO4)3. Perovskite, with the ideal formula CaTiO3, also features isolated SiO4 tetrahedra, although it is often classified as an oxide mineral due to the dominant titanium cation.

The presence of these isolated tetrahedra influences the physical and chemical properties of silikaatrühma minerals. They often have relatively simple crystal structures and can be quite hard and dense. Their cleavage patterns are typically poor or absent because there are no planes of weakness within the mineral structure related to linked tetrahedra. The isolated nature of the silicate units also affects their reactivity and behavior under geological conditions, such as in high-pressure and high-temperature environments. Studying the silikaatrühma is important for understanding the composition and evolution of the Earth's crust and mantle.