Noun
illite (countable and uncountable, plural illites)
(mineralogy) A micaceous phyllosilicate clay mineral with aggregates of grey or white monoclinic crystals.
It has moderate CEC.sfnsfnsfnsfnsfn *Vermiculite is a mica-based clay similar to illite, but the crystals of clay are held together more loosely by hydrated magnesium and it will swell, but not as much as does montmorillonite. Source: Internet
No more than half the clay content should be expansive clays with the remainder non-expansive illite or kaolinite. Source: Internet
Potassium fixation often occurs when soils dry and the potassium is bonded between layers of illite clay. Source: Internet