8 10 and raw shale sample 12 is provided in table 2 below table 2______________________________________mineral 1 2 8 10 12______________________________________smectite 70 30 60 75 mica illite lt 5 lt 5 15palygorskite 50 kaolinite lt 5 chlorite sup 15 sup 2 quartz 15 5 7 10 20cristobalite sup 1 lt 5 13 plagioclase 5 lt 5 lt 5 8feldspark feldspar lt 3 lt 5 lt 3 5clinoptilolite lt 5 lt 5 lt 3 clinopyroxene calcite lt 3 lt 3 lt 5dolomite lt 5 siderite lt 3 gypsum lt 3 lt 2 analcime lt 3 34 amorphous 34 20 30 34 unidentified 34 lt 5 lt 5 lt 5 lt 5 lt 5______________________________________ sup 1 this phase fits the available 34 jcpds 34 joint committee on powder diffraction standards data for cristobalite however a controversy exists over whether this phase occurring in clay samples is truly cristobalite or an 34 opaline silica 34 such as opalct opalct has been defined as 34 microcrystalline cristobalite 34 in a matrix of amorphous silica but this definition is now being questioned the term 34 opaline 34 implies that the phase is hydrated and may not be crystalline or entirely crystalline sup 2 may include a minor amount of kolinite from the data in tables 1 and 2 it is apparent that a.