Reflectance kaolinite

Characterization of Interlayer Water. X-ray diffraction studies of the 10A hydrate show no hkl reflections indicating a lack of regularity in the stacking of the kaolin layers. In addition to the 10A hydrate, two other less hydrated kaolinites were synthesized. Both have one molecule of water for each formula unit in contrast to the 10A hydrate which has two. These less hydrated clays consequently have smaller d(001) spacings of 8.4 and 8.6 A. The synthesis conditions for these two hydrates are described in (22.). By studying the interlayer water in the 8.4 and 8.6A hydrates, it was possible to formulate a model of the water in the more complicated 10A hydrate. 

Figure 4. Indexing texture patterns from crystals of different symmetries (see the text for explanations). Assigning the indices to the reflections is shown in (a) - (c). The splitting of the reflections hkl for different symmetries is shown in (d) - (f). (a), (d) trigonal (lizardite IT), (b), (e) monoclinic (muscovite 2Mi). (c), (f) triclinic (kaolinite).

The production of illite from chemical weathering occurs at all latitudes. It dominates the clay mineral assemblage in the North Atlantic and North Pacific Ocean, particularly at 40° reflecting aeolian transport by the westerlies (Figure 14.11). In the southern hemisphere, the input of illite by the westerlies is diluted by a large input of authigenic montmorillonite in the South Pacific and Indian Oceans and in the South Atlantic by a large input of kaolinite. 

A mixture of intercalating clays is generally found in the subsurface. Interstratification of kaolinite and smectite has been reported in some cases (e.g., Schultz et al. 1971 Lee et al. 1975a, 1975b Yerima et al. 1985). This fact is reflected in an XRD... 

The marked difference in the relaxation times for the kaolinite and silica may be attributed to the nature of the surface. Intuitively, the hydrogen bonding which influences the increased structure at the kaolinite surface would be expected to give shorter values for the relaxation time. However this is not observed in the simulations. Instead, shorter values are seen for the silica surface which is a result of water molecules becoming trapped in the cage-like amorphous silica surface. This reflects experimental results where precipitated silica surfaces are microporous and water inclusion in the surface is common. 

Figure 22. Phases in the muscovite-pyrophyllite join. M = mica-like phase ML = mixed layered phase Mo = fully expandable beidellite Py = pyro-phyllite Kaol = kaolinite Q = quartz All = ordered phase with superstructure reflection.

Figure 29. Possible general phase relations for illite and associated phyllosilicates as a function of varying P-T conditions. Ill = illite, either predominantly IMd or 2M in polymorph I = illite, 2M mica ID = k layer ordered mixed layered phase MLSS = mixed layered 3 or 2 layer ordering giving a superstructure reflection ML0 = mixed layered, ordered structure with no superstructure MLr = mixed layered non-ordered M, = fully expandable montmorillonite Chi = chlorite Kaol = kaolinite Exp 3 " expanding chlorite and/or corrensite.

Pelitic rocks investigated in the same areas where corrensites are formed during alpine metamorphism (Kiibler, 1970) revealed the absence of both montmorillonite and kaolinite but the illite or mica fraction was well crystallized as evidenced by measurement of the "sharpness" of the (001) mica reflection (Kiibler, 1968). This observation places the upper thermal stability of the expandable and mixed layered trioctahedral mineral assemblages at least 50°C. above their dioctahedral correlevants. This is valid for rocks of decidedly basic compositions where no dioctahedral clay minerals are present. 

One set of aluminosilicate equilibrium relationships for which some quantitative data are available is depicted in Figure 5. This figure (25° C) is derived from information presented and discussed by Hemley (15), Feth, Roberson, and Polzer (8), and Garrels and Christ (11). The dual boundaries between potassium mica (muscovite) and kaolinite reflect the roughly estimated uncertainty in the equilibrium constant. The relationship of this boundary to actual K -H+ ratios in sea water may be... 

Chamberlain et al. (1999) measured the oxygen isotope composition of authigenic kaolinite, smectite and illite in weathered horizons from intermontane basins on the east side of the Southern Alps. Neither smectite nor illite produced useful results, as reflected in the... 

In the hard kaolinites there is a positive correlation between mica and books which Hinckley suggests may be due, in part, to sedimentation conditions which favored the simultaneous deposition of books and mica in preference to quartz. This type also has Ti02 positively related to crystallinity. Crystallinity increases as grain size increases. This may reflect a leaching process in which quartz, Fe203 and montmorillonite are removed, Ti02 is concentrated as anatase, and some authigenic kaolinite is formed. 

A12C>3 content, which reflects the presence of clay minerals, shows a distinct maximum in the lower part of this oil shale deposit (Figure lb). It is believed that the clays (kaolinite) reflect a detrital influx into the depositional basin. The P205 content (Figure lc) is quite high (7.3 wt.%) towards the bottom part of the sequence. A deeper sample (167 m),... 

Changes in the vibrational modes of the adsorbent, however, reflect only those changes which occur to the substrate they do not provide direct insight into the structure and bonding of the adsorbed species. In order to examine the influence of the surface on the intercalated species, the vibrational modes of the adsorbate must be obtained. In a previous dispersive-IR absorption study of the kaolinite-hydrazine intercalate, Ledoux and White (17) observed that the ISu hydroxyl groups of... 

In our studies, the model substance (montmorillonite) was a calcium bentonite (Istenmezeje, Hungary), the characteristic features of which are given here. X-ray diffraction (intensity of the basal reflection) and thermoanalytical (weight loss upon heating) data show 91% montmorillonite content. The other constituents are 5% calcite, 3% kaolinite, 1% x-ray amorphous silicates, and a trace of quartz. The amorphous phase is silicate particles, which are not crystalline for... 

The experimental values for the free energies of formation of kaolinite and sepiolite are given in Tbble II. The value of -907.7 +1.33 kcal/mol recommended for kaolinite, is the mean of three recomputed free energies of formation weighed equally in the computation, and was obtained from calorimetry, dissolution, and precipitation data. Several values in the -905 to -906.0 kcal/mol range probably reflect the more soluble nature of small particles typically present in bulk samples. 

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