"ILLCST"@en . "Illite-claystone - A type of monomineralic aluminium-silicate sedimentary rock in which the aluminium-silicate mineral is illite. It is the lithified equivalent of illite-clay. British Geological Survey Research Report RR/99/03, section 9.1 and table 19."@en . . . . "Illite-claystone"@en . . "Illite-claystone"@en . "stable"@en . .