Minerals structural analysis

Applications The general applications of XRD comprise routine phase identification, quantitative analysis, compositional studies of crystalline solid compounds, texture and residual stress analysis, high-and low-temperature studies, low-angle analysis, films, etc. Single-crystal X-ray diffraction has been used for detailed structural analysis of many pure polymer additives (antioxidants, flame retardants, plasticisers, fillers, pigments and dyes, etc.) and for conformational analysis. A variety of analytical techniques are used to identify and classify different crystal polymorphs, notably XRD, microscopy, DSC, FTIR and NIRS. A comprehensive review of the analytical techniques employed for the analysis of polymorphs has been compiled [324]. The Rietveld method has been used to model a mineral-filled PPS compound [325]. 

Soil solids are either inorganic or organic, and each requires different analyses. Direct measurements on whole soil are not as common as indirect measurements. Direct measurements are limited to X-ray, IR, and NMR analysis. X-ray analysis is commonly used to investigate mineral structure, while IR is used to... 

Zvyagin B.B. (1967) Electron diffraction analysis of clay mineral structures. New-York, Plenum. 

The phyllic alteration zone coincides with a subtle but consistent shift in the dominant AlOH peak in the short-wave infrared spectrum ( 2210 nm) to slightly lower wavelengths, consistent with an inner white mica-ferroan carbonate mineral assemblage. A preliminary analysis of hyperspectral data over the visible to near infrared range suggests that ferroan carbonates may be detected but not reliably quantified. However, TIR data allow calcite and ferroan carbonate to be distinguished, and may also detect increasing Fe content in ferroan dolomite as mineralized structures are approached. 

In the remainder of this chapter, specific examples of fibrous minerals are presented. The chemical formulas are given as well as the mineral names. A formula is a shorthand notation that describes the elemental composition of the compound plus the specific ion associations, as determined by three-dimensional structure analysis of the species. Because every mineral sample is not completely analyzed, an ideal formula—one that summarizes the chemistry and associations of the ions—is usually presented. 

In the geosciences Raman spectroscopy has traditionally been a laboratory tool for structural analysis of minerals. Recent developments in instrumentation make possible the use of Raman spectroscopy as a tool for routine identification of minerals in field situations. The following advantages characterize Raman analysis of minerals no sample preparation in situ real time measurement non-destructive and non-intrusive sampling samples may be transparent or opaque spectra are well resolved and with high information content. 

A rich variety of crystal structures are made possible by hydrogen bonding. The variety is comparable to that found amongst the silicate minerals, and it is similarly based on a limited number of simple structural themes. We illustrate a few of the pattern-types revealed by crystal-structure analysis. 

The development of reliable methods for structural analysis of mixtures is very laborious. Physical data of pure compounds may serve as a base for the investigations. It has, however, been proved that not in all cases can these data be simply correlated with those of the mixtures. Thus correlations of physical data of pure, individual hydrocarbons often prove not to be valid in the analysis of mineral oils. In this case physical constants of mineral oil fractions of widely different origin form a more reliable basis for the structural analysis, provided that their structure has been determined by absolute methods. 

It should be pointed out that this method for ring analysis and branching analysis is based exclusively on reliable data of n, d, M and a of pure individual hydrocarbons, and holds, within the limits of accuracy of the determination, for widely differing types of branched as well as non-branched saturated hydrocarbon mixtures. It is particularly recommended for the structural analysis of saturated polymers, where other statistical methods (w- -M-method, v-n-d-method, etc.) fail because they have been developed for mineral oils, and are based on correlations of physical data of mineral oil fractions that always show approximately the same small degree of branching 1-2 branchings per molecular weight = 100. 

The application of several methods for structural analysis of mineral oils is, in general, limited to those fractions in which no structural elements are present in larger quantities than normally occur in mineral oil fractions. In highly aromatic concentrates, for instance, the normal analytical methods (n-d-M v-n-d) may give inaccurate results, because different types of aromatics may influence the physical constants of the oil differently. 

Cathodoluminescence observations by themselves reveal details of texture among minerals and suggest chemical or structural variation within individual grains. Seldom can the CL observations be interpreted without additional information such as chemical or structural analysis. With this in mind, data obtained from the electron microprobe (EMP), ion microprobe (IMP), scanning electron microscope (SEM), or by thermoluminescence studies complement CL observations and many of the CL examples for meteorites can be best interpreted or related to mineralogy through these data. 

Chemical—structural analysis and leachability tests on scum, slag, and Fe-minerals were carried out to characterize and measure the chemical stability of the metals in waste materials. The investigation was designated to (1) evaluate the... 

The arsenate polyhedra, on the other hand, show distinctly more variability of the > 60 species described,270 many of which are minerals, structural analyses are available for one-third and, of these, one-third appear to have non-octahedral Mn polyhedra (Table 25). (The proviso results from a report268 that the earlier analysis, describing arsenoclasite as containing [Mn04], [MnOs] and [MnOs] polyhedra, was in error, and that there are only [MnOs] polyhedra—albeit distorted.)... 

B. B. Zvyagin, Electron-Diffraction Analysis of Clay Mineral Structures , Plenum Publishing, 1967. 

Mellini, M., Merlino, S., Pasero, M. (1986). X-ray and HRTEM structure analysis of orientite. Amer. Mineral., 71, 176-87. 

Andrault D., Piquet G., Charpin T., and Bihan T. L. (2000) Structure analysis and stability field of beta-iron at high P and T. Am. Mineral. 85, 364-371. 

The existence of surface" bivalent cations at lattice positions with 3-fold coordination in the large cavities (Site 2) exposed to adsorbed molecules was shown from a structure analysis of a Ca-exchanged fauja-site single crystal (12, 30). The assignment of Ca ions to various lattice positions in mineral faujasite helped to explain by comparison the observation that with Y zeolite the catalytic activity emerges at approximately 50% Ca exchange, because of the preference of Ca ions for the fully... 

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