Other mixed-layer clay minerals

Two sediments from the bituminous subunit (NR-10, 151 and 170 m) are almost free of carbonate. Opal and quartz are dominant in these samples and are accompanied by mixed-layer clay minerals, kaolinite and illite. In the most organic-carbon-rich sediment (NR-10, 170.5 m 25.5% C ) opal is present as amorphous opal A and not as opal CT like in the other sample. Furthermore, the carbonate signals in the X-ray diffractogram are extremely broad. This indicates that the minerals in this sediment are diagenetically less altered than those in the other samples studied. 

The most widespread fill material is reddish brown (2.5 YR 4/4, 5 YR 4/4) loam with a minor admixture of relatively large oolitic bauxite pebbles (derived from the Late Triassic - Camian - beds) and coarse clasts of black chert. Pilot X-ray diffraction analysis revealed mostly muscovite/illite, plus mixed-layer clay minerals of illite/montmorillonite type, chlorite plus mixed-layer clay minerals of chlorite/montmorillonite type, calcium montmorillonite, and diaspore plus gibbsite, or just traces of bauxite minerals (Misic, 2000). The mineral composition is not as uniform as might be expected, and further research, intended for application of factorial analysis, is in progress. A potential sediment source area in the present Cerkniscica River basin (Fig. 1) appears obvious at first glance, but similar outcrops of bauxite and chert do also appear at other sites that are not much more remote. 

The suite of minerals occurring as impurities in U.S. coals of commercial quality is moderately consistent this suite includes quartz, calcite, pyrite, various clay minerals including kaolinite, illite, and varieties of illite-smectite mixed-layer clay minerals. The weathering of pyrite produces some sulfate minerals in many coals. Several other minerals are present in most coals in trace amounts. 

For samples taken up-dip of the Setif and Medjounes areas the values range from +2.9 to -5.8%o (Tables 7.2,7.3 Fig. 7.2). The light carbon makes itself felt in the carbonates where we find traces of recrystallization or of other mineralogical neoformations and in particular the appearance of mixed-layer clay minerals with perfectly ordered crystal structures. In the same samples microfissures are filled by secondary calcite or dolomite with detrital carbonate cement frequently being present between the crystals. In other cases we observe entire fields of neoformed minerals (dolomite... 

Clays are volumetric ally the most abundant mineral group in coal. They can be authigenic or detrital in origin. Kaolinite is the most common clay and the most common authigenic mineral in coals. The silicon and aluminum in kaolinite are, perhaps, residual from the dissolution of ferromagnesian minerals and feldspars. Illite and mixed layer clays in coal are almost exclusively detrital in origin. Chlorites, smectites, and other clay minerals may be abundant locally. 

Trioctahedral Chlorite. This is encountered in virtually all fine-grained fractions of the sections studied. There are no swelling layers in the structure of this mineral which exhibits a high degree of crystallinity. The d(o6o) reflex at 1.532 A indicates that the chlorite is trioctahedral. There are no mixed-layer clays of the chlorite-montmorUlo-nite type, nor swelhng chlorites nor, in view of the lack of any other structure, any minerals containing hydrate-sheets between their layers. 

IHite/Smectite. Another common intergrowth of sheet silicates is the mixed-layering of illite and smectite. As discussed above, illite and smectite are clay minerals whose basic structures resemble the mica muscovite. Their compositions may differ significantly from muscovite, but they generally have a lower occupancy of the interlayer sites than mica. Numerous other compositional differences are possible for smectite however, this discussion will be restricted to a dioctahedral illite and a dioctahedral smectite containing potassium and vacancies in the interlayer sites as given above. 

In addition to sparingly soluble metal (hydr)oxides, salt type materials involving two such oxides or more, and clay minerals, whose crystallographic and thermochemical data are presented in Chapter 2, the zero points of zeolites, clays, and glasses are listed (in this order) after mixed oxides. Soils and other complex and ill-defined materials are on the end of the list. It should be emphasized that the terms soil , sediment", etc. have somewhat different meanings in different scientific and technical disciplines. This may lead to confusion, e.g. terms kaolin (clay) and kaolinite (clay mineral) are treated as synonyms in some publications. The zero points obtained for composite materials with a layer structure (core covered by coating) are listed separately from those in which the distribution of components is more uniform. 

The term clay refers to fine-grained aluminosilicates that have a platy habit and become plastic when mixed with water [11], Dozens of minerals fall under the classification of clays and a single clay deposit can contain a variety of individual clay minerals along with impurities. Clay minerals are classified as phyllosilicates because of their layered structure [12], The most common clay mineral is kaolinite, although others such as talc, montmorillonite, and vermiculite are also abundant. Each of the... 

Clay constitutes the most abundant and ubiquitous component of the main types of marine sediments deposited from outer shelf to deep sea environments. The clay minerals are conventionally comprised of the <2 pm fraction, are sheet- or fiber-shaped, and adsorb various proportions of water. This determines a high buoyancy and the ability for clay to be widely dispersed by marine currents, despite its propensity for forming aggregates and floes. Clay minerals in the marine environments are dominated by illite, smectite, and kaolinite, three families whose chemical composition and crystalline status are highly variable. The marine clay associations may include various amounts and types of other species, namely chlorite and random mixed layers, but also ver-miculite, palygorskite, sepiolite, talc, pyrophyllite, etc. The clay mineralogy of marine sediments is therefore very diverse according to depositional environments, from both qualitative and quantitative points of view. 

Other clay minerals are also able to bear a clear climatic message, as for instance the amount of random mixed layers and altered smectite in temperate regions, the crystalline status of illite in temperate to warm regions, and the abundance of soilforming Al-Fe smectite in subarid regions. Detailed measurements on X-ray diffraction diagrams, electron microscope observations and geochemical analyses allow precise characterization of the different continental climatic environments from data obtained on detrital sedimentary clays. 

The clay mineral spectrum is notably less differentiated than in the other facies, the dominant minerals being trioctahedral chlorites and dioctahedral illites. In the chlorite structure, non-swelling layers predominate whereas the alternation of layers of different types exhibits a trend towards ordering. The proportion of mixed-layer minerals of the iUite-montmorillonite type decreases especially as one approaches the massive layers of rock salt. 

Kurokawa et al. [258-260] developed a novel but somewhat complex procedure for the preparation of PP/clay nanocomposites and studied some factors controlling mechanical properties of PP/clay mineral nanocomposites. This method consisted of the following three steps (1) a small amount of polymerizing polar monomer, diacetone acrylamide, was intercalated between clay mineral [hydrophobic hectorite (HC) and hydrophobic MMT clay] layers, surface of which was ion exchanged with quaternary ammonium cations, and then polymerized to expand the interlayer distance (2) polar maleic acid-grafted PP (m-PP), in addition was intercalated into the interlayer space to make a composite (master batch, MB) (3) the prepared MB was finally mixed with a conventional PP by melt twin-screw extrusion at 180°C and at a mixing rate of 160 rpm to prepare nanocomposite. Authors observed that the properties of the nanocomposite strongly dependent on the stiffness of clay mineral layer. Similar improvement of mechanical properties of the PP/clay/m-PP nanocomposites was observed by other researchers [50,261]. 

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