Clay minerals, definition

Electronegativity, 7,10, 117 Mobility, 400-403 Chlorinated hydrocarbon, 345-352 Chlorite, 104,114 Clay minerals, definition, 102 Complexation, 65, 66 Concentration, 45 Conductance of ions, 80 Conductivity, 81... 

ClassiTication Complex silicate clay mineral Definition Specific type of Fuller s earth Formuia AljOj ASiOj HjO... 

A specific example of this would be the weathering of K-feldspar and the formation of kao-linite (see Table 8-1 for mineral definitions), a layer-silicate clay ... 

The clay fraction, which has long been considered as a very important and chemically active component of most solid surfaces (i.e., soil, sediment, and suspended matter) has both textural and mineral definitions [22]. In its textural definition, clay generally is the mineral fraction of the solids which is smaller than about 0.002 mm in diameter. The small size of clay particles imparts a large surface area for a given mass of material. This large surface area of the clay textural fraction in the solids defines its importance in processes involving interfacial phenomena such as sorption/desorption or surface catalysis [ 17,23]. In its mineral definition, clay is composed of secondary minerals such as layered silicates with various oxides. Layer silicates are perhaps the most important component of the clay mineral fraction. Figure 2 shows structural examples of the common clay solid phase minerals. 

No new definitions will be proposed here but a simple outline of the basic vocabulary is given which will be used to permit a discussion of the problems of physical chemistry of phyllosilicates and other silicate minerals found in clay mineral suites. 

The definition of perfectly mobile and inert components should also be valid for cases of ionic diffusion in rocks and where no fluid is involved (Korzhinskii, 1965), but this possibility does not concern us here since clay mineral equilibria are dominated by the presence of liquid or fluid aqueous solutions. 

During the process of lithification and deep burial illite appears to remain stable or at least is slow to react with other minerals. It is by far the most dominant species of clay mineral in argillaceous sedimentary rocks (Grim, 1968 Millot, 1964). In early burial, the overall illite content of a specimen may decrease during adjustment to bulk chemical and physical restraints (Perry and Hower, 1970) however most studies of deeply buried sediments show a definite increase in illite as pressures and temperatures increase (Millot, et al., 1965 Dunoyer de Segonzac, 1969 ... 

One of the few clay minerals to be identified as definitely having an origin at the sediment-water interface is glauconite, i.e., the green micaceous material which forms pellet-like agglomerates. This has been conclusively demonstrated in recent sediments (Porrenga, 1967b Lamboy,... 

The layers may be regularly or randomly interstratified. The latter are by far the more common and are probably the second most abundant clay mineral species, following illite (which in most cases is a mixed-layer clay). More regularly interstratified clay minerals have a definite periodicity and some are given specific mineral names. The randomly interstratified clay minerals are described in terms of the type and proportion of the two or more types of layers. Many of them exhibit some degree of regular interlayering. 

Thus, the secant relationship (4.20) with the angular definition modified for aluminosilicates (MacKenzie et al. 1985) has been used to shed light on the possible existence of a Si-Al spinel suggested to form when the clay mineral kaolinite is heated to 980°C. On the basis of the known structure of the closely-related 7-alumina spinel, the T-O-T angle of the postulated tetrahedral Si site in such a structure predicts a chemical shift of - 79 ppm for this site. Such a resonance would normally be masked by the broad resonance of the amorphous Si02 also present, but when this material was selectively removed by leaching with KOH solution, the predicted Si peak was detected (MacKenzie et al. 1996) (Figure 4.13). Measurements of the relative intensity of this... 

There is no geological or chemical definition of an oil shale. Any rock yielding oil in commercial amount upon pyrolysis may be considered as an oil shale. The composition of the inorganic fraction may vary from a shale where clay minerals are predominant, such as the Lower Jurassic shales of Western Europe (particularly France and West Germany.), to carbonates with subordinate amounts of clay and other minerals, such as the Green River shales of Colorado, Utah and Wyoming. 

It is common practice to make a distinction between the inorganic constituents of so-called "Eastern" and "Western" coals By definition. Western coals are those for which the CaO+MgO content exceeds the Fe203 content of the ash, while the reverse is true for Eastern coals [ 1 I The inorganic constituents in Eastern coals, which are principally bituminous in rank, are predominantly in the form of discrete mineral particles. Clay minerals (kaolinite, illite) are usually dominant, followed by quartz and pyrite. The range and typical values of the mineral distribution and ash chemistry of Eastern coals are shown in Table I. These data were determined from computer-controlled scanning electron microscopy (CCSEM), Mossbauer spectroscopy, and other measurements on over a hundred coals. 

The present study is focused on materials with variable (pH-dependent) surface charge, and the methods and definitions are adjusted to this type of materials. Clay minerals and other materials with a dominant role of permanent charge need a different approach. Clay minerals do not show a clear CIP of charging curves... 

Any mineral with a particle size of < 2 m is, by definition, part of the clay fraction of a soil. However, the term clay mineral has a different connotation historically, usually referring to the secondary layer silicates, which are the dominant inor-... 

In 1966, Seki (36) proposed a new facies, the wairakite facies, characterized by the occurrence of wairakite-quartz with clay minerals, in the absence of prehnite or pumpellyite. On field, experimental, and thermodynamic grounds, this proposed facies evidently represents, at least for conditions where PH2o = Pfiuid, higher temperatures than the laumontite assemblages, and relatively low pressure. Subsequently, Seki (35) introduced separate mordenite, heulandite, and laumontite facies. Our earlier definition of the zeolite facies was intended to be broad... 

As reference values, Table 3b also presents the amounts of C oxidized after 30 or 120 min for pure tannic acid pp and for the C-pp model. It is evident that, in the absence of an efficient complexing cation, the whole amount of organic C is definitively oxidized within 120 min. Interestingly, in the C-pp model, the large amount of C already oxidized after 30-min could be ascribed to a possible priming catalytic effect by the clay mineral differently, the flakes of pure pp probably clotted, thus needing more time to be completely oxidized [15]. 

Kroschurtz, J. S., (1993). Ed. For definitions and background on layered silicate and clay minerals, see Kirk-Othmer Encyclopedia of Chemical Technology, 4th ed. John Wiley and Sons New York Vol. 6. 

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