The neutral aluminium hydroxide sheets are found sandwiched between silicate sheets in important clay groups : the illite, kaolinite, and montmorillonite / smectite groups.
32.
The main rock types are sandstone and limestone, and the soil is composed almost exclusively of quartz sand grains and clay minerals ( illite ).
33.
Width of the illite XRD peak at one half of its height is collected and recorded with units of " ?? ( XRD angle ).
34.
Minerals formed by alteration processes include alunite, calcite, cristobalite, illite, jarosite, kaolinite, pyrophyllite, quartz, smectite, sulfur and tridymite.
35.
Greensands are green because of iron-bearing glauconite which is usually recognized as illite / mica or mixed layer illite-smectite clay by x-ray diffraction.
36.
Greensands are green because of iron-bearing glauconite which is usually recognized as illite / mica or mixed layer illite-smectite clay by x-ray diffraction.
37.
If the illite crystallinity values fall in the 0.42-1.0 ?? range, it corresponds with a metamorphic deep diagenetic zone or zeolite facies.
38.
If the illite crystallinity values fall in the 0.25-0.30 ?? range, it corresponds with a metamorphic high anchizone or prehnite-pumpellyite facies.
39.
If the illite crystallinity values fall in the 0.30-0.42 ?? range, it corresponds with a metamorphic low anchizone or prehnite-pumpellyite facies.
40.
In stratigraphy and tephrochronology, completely devitrified ( weathered volcanic glass ) ash-fall beds are commonly referred to as K-bentonites when the dominant clay species is illite.
