Illite group

Another member of the illite group is hydrous mica, in which the principal interlayer cation is K. A smectite you might encounter is montmorillonite smectites can expand by incorporating water or organics between the structural layers. Vermiculite is derived from the Latin vermiculare, which means to breed worms, and describes what appears to happen when the material is heated rapidly. Otherwise it is very similar to phlogopite mica. As you would guess, most of these minerals have complex chemical compositions. 

The illite group minerals have a structure similar to that of muscovite, but there is less substitution of Sr by in the tetrahedral sites. As a consequence,... 

The basal spacing of illite is 10 A. The K, Ca or Mg interlayer cations prevent the entrance of H2O into the structure. For this reason the basal spacing in illite is constant. Thus, the illite group minerals cannot expand by absorption of water like halloysite, vermiculite and smectite. 

Kodama and Brydon [631] identify the dehydroxylation of microcrystalline mica as a diffusion-controlled reaction. It is suggested that the large difference between the value of E (222 kJ mole-1) and the enthalpy of reaction (43 kJ mole-1) could arise from the production of an amorphous transition layer during reaction (though none was detected) or an energy barrier to the interaction of hydroxyl groups. Water vapour reduced the rate of water release from montmorillonite and from illite and... 

Sorption depends on Sorption Sites. The sorption of alkaline and earth-alkaline cations on expandable three layer clays - smectites (montmorillonites) - can usually be interpreted as stoichiometric exchange of interlayer ions. Heavy metals however are sorbed by surface complex formation to the OH-functional groups of the outer surface (the so-called broken bonds). The non-swellable three-layer silicates, micas such as illite, can usually not exchange their interlayer ions but the outside of these minerals and the weathered crystal edges ("frayed edges") participate in ion exchange reactions. 

Fig. 7 shows the progressive transformation of montmorillonite to iliite/smectite interlayers by the gradual development of both the characteristic Cs and Rb high selectivity profiles observed for pure illite and the high Cs-Rb selectivity at+ race fadings. The data can be simulated (see table VI for the Ca - Cs case) using a consistent set of intrinsic selectivity coefficients and identical site group capacities for the Ca-Cs and... 

The aluminosilicates examined were chosen as end members of those groups of phyl losil icates that commonly occur in soils muscovite and biotite mica, Fithian and Morris illite, Montana vermicul ite, montmoril Ionites from Upton (Wyoming bentonite), Camp Berteau, Redhill and New Mexico, and kaolinites from St. Austell, England, and Georgia, U.S.A. 

In the Goldenville Group, the Moshers Island Formation also has two compositional members an upper one explained by mixtures of chlorite, kaolinite illite, and smectite, and a lower one explained by only illite and smectite. 

In contrast, metawackes in the Government Point, Green Harbour, and Moses Lake formations (Goldenville Group) have compositions explained by mixtures of illite, albite, and quartz, but each of the these formations differ slightly in terms of the amounts of quartz and feldspar they contain, relative to illite. In addition, the Moses Lake Formation contains significant amounts of chlorite. 

These unconformity-type deposits are located around the unconformity between the Helikian Athabasca Group sandstones and underlying Archean to early Proterozoic metamorphic basement (Hoeve Sibbald 1978 Hoeve Quirt 1984). The present sandstone cover ranges from 0 to 1500 m in thickness and is dominantly composed of mature coarse-grained quartz arenite with a kaolin-illite clay matrix. 

High amounts of Ca (and potentially Ra), Sr, and LREE were co-precipitated by Al-phosphates from the crandallite group, which crystallized in the clay halo. Clay minerals (mainly chlorite and to a lower extent illite) and Ti-oxide were found to have sorbed significant amounts of uranium. Sorption onto mineral surfaces was followed by the formation of coffinite, USi04-nH20, rimming clay, and rutile particles. 

Probably the most passionately debated mineral (if one might use this adverb in a discussion of clays) found in argillaceous sediments, rivalling perhaps the enigmatic dolomite and dolomitization in the realm of sedimentary rocks, is the mineral or group name illite. Defined and redefined by its originator, R. E. Crim debated and further redefined, denied a proper existence and reprieved, this species has attracted the attention of clay mineralogists for the past two decades. It represents, in fact, the dominantly potassic, dioctahedral, aluminous, mica-like fraction of clay-size materials. Known as sericite or hydro-mica in studies of hydrothermal alterations, soil mica or illite in soils and illite... 

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