The behavior of the mineral reflections under natural conditions
(air-dried, ethylene glycolated and heating to 335 °C and 550 °C) de-
fines a very diverse set of clay minerals represented by illite, smectites,
interstratified illite/smectite, kaolinite and chlorites. Based on the type
(and association) of the clay minerals, the studied samples can be divided
into five groups.