Illite 
A 2:1 layer clay mineral. Silicates, such as feldspar, is weathered to form this clay mineral, with alkaline pH and high concentrations of potassium and aluminium being typical outcomes.
Illite
A 2:1 layer clay mineral. Silicates, such as feldspar, is weathered to form this clay mineral, with alkaline pH and high concentrations of potassium and aluminium being typical outcomes.