Chemical composition of minerals

Table 5.17. Molar chemical composition of minerals in the assemblage quartz (qz)- muscovite (ms)- K-feldspar (Kf)-sillimanite (sil) - water (w).

Table 5.19. Molar chemical composition of mineral end-members in the assemblage of Table 5.18. See text for abbreviations.

For definitions of units, chemical composition of minerals, chemical formulae of molecules and time spans of geologic periods, see the Appendices. 

Table I. Approximate Chemical Composition of Minerals Discussed...

This list is organized according to the chemical composition of mineral species. The simplest, the native elements, are first, followed by progressively more complex minerals. This list only includes those species that are used as gems or ornamental materials. Organic substances, such as amber and jet, are not included and will be addressed elsewhere. 

The chemical composition of minerals was determined in 29 polished carbon-coated thin sections using a Cameca Camebax BX50 microprobe equipped with three spectrometers and a back-scattered electron detector (BSE). Operating conditions were 20 kV acceleration voltage, 8 nA (for carbonates and clay minerals) to 12 nA (for feldspars) measured beam current, and a 1-10 pm beam diameter (depending on the extent of homogeneous areas). Standards and count times were wollastonite (Ca, 10 s), orthoclase (K, 5 s), albite (Na, Si, 5 and 10 s, respectively), corundum (Al, 20 s), MgO (Mg, 10 s), MnTiOj (Mn, 10 s) and hematite (Fe, 10 s). Precision of analysis was better than 0.1 mol%. 

The chemical composition of minerals was determined in a total of 17 polished, carbon-coated thin sections. A Cameca Camebax BX50 microprobe equipped with three spectrometers and a back-scattered electron detector (BSE) was used for quan-... 

It has been noted that the chemical composition of minerals could vary within specified limits. This phenomenon is known as sofid solution. For example, the chemical composition of the mineral dolomite is commonly designated as CaMg (C03)2, or as (Ca, Mg)CO. This does not mean that dolomite has calcium and magnesium existing in a one-to-one ratio. It signifies that dolomite is a carbonate mineral that has significant amounts of... 

J. Camilleri, The chemical composition of mineral trioxide aggregate, J. Conserv. Dent. 11 (2008) 141-143. 

Boroughs TJ, Faure G, Buchanan D (1992) Chemical compositions of minerals of the ordinary (H6) chondrite, RKP 86701, from the Reckling Moraine. Antarctic J US 27 (5) 30-31 Bradley JP (2005) Interplanetary dust particles. In Davis AM (ed) Meteorites, comets, and planets. Elsevier, Amsterdam, The Netherlands, pp 698-713... 

During the late nineteenth century, scientists had theorized that the external crystal forms of minerals reflected the ordered internal arrangement of their atoms. In the early twentieth century, this theory was confirmed through the use of X rays. Also, it became possible to chemically analyze minerals and rocks so that chemical mineral classifications could be further developed. Finally, in the 1960 s, the use of many instruments such as the electron microprobe allowed geologists to determine variations in chemical composition of minerals across small portions of the minerals so that models for the formation of minerals could be further developed. 

Fe-minerals and sulfides are common in hydrothermal ore deposits. If we know these mineral species, chemical compositions of minerals and temperature, fo2-pH and Eh-pH conditions can be restricted. As an example of the estimates of foj and pH, vein-type deposits in Japan are taken into account. The vein-type deposits considered here include precious metal (Au, Ag) and base metal (Cu, Pb, Zn, Fe, Mn) deposits and are classed as epithermal-type (Shikazono 2003). The oxidation-reductimi conditirm can be estimated based on mineral assemblages and chemical compositions of minerals. Sphalerite is the most conunon sulfide mineral in these deposits. It contains iron and is zinc-iron solid solutimi (Zni xFexS). The relationship among FeS content of sphalerite, foj, pH and temperature is obtained from the reaction. 

The nanosized HA building block in dentin is smaller than that of enamel, being about 25 nm wide, 4nm thick and 35 nm long. Dentin is similar to bone in many respects, including a similar composition and hierarchical structure up to the level of the lamellae bone hence, most of the statements made above relating to bone are equally applicable to dentin. Although the chemical composition of mineral in... 

X-ray fluorescence analysis has been widely used in determining the chemical composition of minerals, and a recent development of this technique, the microprobe X-ray fluorescence analyzer, can be used to study variations in chemical composition over very small areas. Volumes as small as 1 / m can be analyzed, making possible the detection and analysis of very small inclusions. 

None of the natural sulfides of manganese are of any commercial importance. Some siUcates have been mined. Rhodonite and braunite are of iaterest because these are frequendy associated with the oxide and carbonate minerals. The chemical composition of some common manganese minerals are given ia Table 3. 

The complexity of amphibole geology and stmcture is readily understood from their chemical composition. The average chemical composition of amphibole minerals may be represented as (2) ... 

Cathode Reaction. There are many different types of manganese dioxide (18), having varying activity in batteries. The only type suitable for alkaline batteries is y-Mn02, the mineral form of which is nsutite. The chemical composition of has been described (19) by the general formula... 

The chemical composition of vermiculite can be quite variable (145). The megascopic varieties are generally trioctahedral, and the clay-si2e varieties contain both dioctahedral and trioctahedral varieties (144). Smectite minerals do not commonly occur as macroscopic single crystals. 

Widdowson EM, Dickerson JWT. 1964. Chapter 17 Chemical composition of the body. In Comar CL, Bronner F, eds. Mineral metabolism An advanced treatise. Volume II The elements Part A. New York, NY Academic Press. 

Assuming chemical equilibrium between Kuroko-forming minerals and Kuroko ore fluids, the chemical composition of Kuroko ore fluids can be estimated, using thermochemical data. Calculations for the purposes of estimating the chemistry of Kuroko... 

Chemical composition of Kuroko ore solution, estimated ba.sed on the solubility data of Kuroko forming minerals (Shikazono, 1985c)... 

Origin of ore fluids is constrained by (1) chemical compositions of ore fluids estimated by thermochemical calculations (section 1.3.2) and by fluid inclusion analyses, (2) isotopic compositions of ore fluids estimated by the analyses of minerals and fluid inclusions (section 1.3.3), (3) seawater-rock interaction experiments, (4) computer calculations on the seawater-rock interaction, and (5) comparison of chemical features of Kuroko ore fluids with those of present-day hydrothermal solutions venting from seafloor (section 2.3). 

In the last two decades, great progress has been made in the field of hydrothemal alteration studies, mainly from computation works on water-rock interactions at elevated temperatures (e.g., Wolery, 1978 Reed, 1983, 1997 Takeno, 1989). These studies revealed the relationship between the changes in chemical composition of hydrothermal solution and the relative abundance of minerals in the rocks. 

There are different approaches to the study of hydrothermal alteration. For instance, Shikazono (1978a) showed the relationship between chemical composition of hydrothermal solution in equilibrium with the alteration minerals and Cl concentration in hydrothermal solution. 

Giggenbach (1984) calculated the effect of temperature on the chemical composition of fluids buffered by alteration minerals. The causes for the hydrothermal alteration considered below are mainly based on the works by Shikazono (1978a) and Giggenbach (1984). The effect of the extent of water-rock interaction is not taken into account. 

Figure 1.86 illustrates the variations in the chemical composition of chloride-rich hydrothermal solution in equilibrium with common alteration minerals with temperature. Figure 1.86 demonstrates that (1) the chemical compositions of hydrothermal solution... 

The chemical compositions of opaque minerals (sphalerite, electrum) are different in two types of deposits. The FeS content of sphalerite from vein deposits of the Te-type is generally lower than that of the Se-type (Fig. 1.118). However, FeS content of sphalerite from massive deposits of the Te-type (Kobetsuzawa, Suzaki) is high, ranging from 1 to 7 mol%. The Ag content of electrum from the Se-type is higher than that from the Te-type (Fig. 1.119). 

The dependence of concentration of K+, Na+, Ca + and H4Si04 in equilibrium with common alteration minerals (K-feldspar, Na-feldspar, quartz) on temperature is shown in Fig. 1.140 (Shikazono, 1988b). This figure demonstrates that (1) chemical compositions of hydrothermal solution depend on alteration minerals, temperature and chloride concentration, and K" " and HaSiOa concentrations increase and Ca + concentration decrease with increasing of temperature. In this case, it is considered that potassic alteration adjacent to the gold-quartz veins occurs when hydrothermal solution initially in... 

Stannite is the most common tin sulfide mineral in the ore deposits associated with tin mineralization. This mineral sometimes contains appreciable amounts of zinc, together with iron. Several workers have suggested that the zinc and iron contents of stannite are related to temperature. With respect to the study of the phase relationships in the pseudobinary stannite-kesterite system. Springer (1972) proposed zincic stannite as a possible geothermometer mainly based on the chemical compositions of the two exsolved phases (stannite and kesterite). Nekrasov et al. (1979) and Nakamura and Shima (1982) experimentally determined the temperature dependency of iron and zinc partitioning between stannite and sphalerite. 

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