Illite

Illite is the name for a series of clay minerals. The name comes from the U.S. state of Illinois, where illite was first described. There are three-layer silicates, layer consisting of an aluminum (Al) octahedral layer and two surrounding silicate (Si) tetrahedral layers. They are structurally very similar to the micas and also arise from these, and other silicates ( feldspar, Foide and others).

Illite arise mainly from smectites ( swellable clay minerals ) by the incorporation of potassium between the layers during diagenesis of sediments.

The general chemical formula K0, 65Al2, 0Al0, 65Si3, 35O10 (OH ) 2 In contrast to the real micas such as muscovite and biotite, a charge deficiency is in the intermediate layers, that is, due to the small amounts of potassium, which are installed therein. Illite formed during the chemical weathering of muscovite, but also of feldspar and other aluminum-rich minerals. Illite is a very common mineral in pelites and siltstones. Changes in the crystal lattice with increasing temperatures and pressures are used to estimate the depth of burial of sedimentary rocks, the so-called Illitkristallinität.

Illite is expected to the group of clay minerals.