Aluminosilicates

ALUMINOSILICATES (EN: aluminosilicates, alumosilicates; DE: Alumosilikate; FR: aluminosilicates, alumosilicates, silicates d'alumine; ES: silicatos de aluminio; RU: алюмосиликаты) are the minerals of the class of the natural silicates. There exist within the crystal structure of the aluminosilicates, along with the silicon-oxygen SiO4 tetrahedra, also the aluminium-oxygen AlO4 ones. The aluminium- and silicon-oxygen tetrahedra, which are interconnected by the common atoms of oxygen, form either the infinite three-dimensional framework, or the flat networks, and much rarely the rings, single or double chains. Respectively, the aluminosilicates belong to the framework-shaped (feldspars, feldspathoids, scapolite, zeolites, pollucite, petalite, and others), layered (micas, chlorites, prehnite, clayish minerals of the montmorillonite group), and less often ring-shaped (cordierite), chain-shaped (certain pyroxenes, for example, augite), or tape-shaped (certain amphiboles, for example, hornblende) silicates.

The ratio Ai:Si is at most 1:3 within the chained (tape-shaped) aluminosilicates, 1:1 within the framework-shaped and layered. The atoms of Al may be distributed within the crystal lattice of the aluminosilicates randomly (statistically) or occupy strictly determined crystal-chemical positions, thus there is characteristic for the aluminosilicates the varying degree of the structural ordering, which is depending on the temperature and the rate of the crystallization, the regime of the volatile substances, and other factors. There predominate among the cations within the constitution of the aluminosilicates the Na, K, Ca; Mg and Fe play somewhat lesser role; Li, Ba are detected less often. Most aluminosilicates represent themselves as the light-coloured light-weight (density is less than 2890 kilograms per cubic metre) minerals.

Aluminosilicates are the rock-forming minerals, one of the major constituent parts of the most rocks of the Earth crust, namely, igneous (except ultrabasic), metamorphic, clastic, and sedimentary. In total, aluminosilicates form more than 50% of the volume of the upper part of the lithosphere. There belong to aluminosilicates the 65-75% (by volume) share within the constitution of granites. Many aluminosilicates (alkaline feldspars, certain micas, nepheline, lapis lazuli, petalite, pollucite, and others) are valuable mineral raw material.