Other Titanium Bearing Minerals

Groups of Ti bearing minerals have been studied by Gaft et al. (1981) and the broad bands in the blue-green part of the spectriun have been connected with individual TiOe luminescence centers and their clusters, while the yellow band was ascribed to a Ti center (Fig. 4.36). 

Ionic radii of zinc are of 0.74 A in 4-coordinated form and 0.88 A in 6-coordinated form. The main substituting liuninescence centers are Mn + and 

Hydrozincite is anhydrous carbonates. The crystalline system is monoclinic-prismatic with the space group C2/m. The structure is composed of Zn in both octahedral and tetrahedral coordination, in the ratio 3 2. The octahedral Zn atoms form part of a C6 type sheet with holes. The octahedral Zn atoms occur above and below these holes. The natural hydrozincite in our study consisted of three samples. Concentrations of potential luminescent impurities are presented in Table 4.13. The laser-induced time-resolved technique enables us to detect Pb center (Fig. 4.37). 

Ionic radii of zirconium are of 0.73 A in 4-coordinated form and 0.86 A in 6-coordinated form. The possible substituting luminescence centers are Ti with an ionic radius of 0.75 A in 6-coordinated form, TR +, Cr +, Cr +, Mn , and Fe. Impurities ofU and Th are also possible, which may radiatively decay with formation of radiation induced luminescence centers. 

Hydrozincite is anhydrous carbonates. The crystalline system is monoclinic-prismatic with the space group C2/m. The structure is composed of Zn in both octahedral and tetrahedral coordination, in the ratio 3 2. The octahedral Zn atoms 

The natural hydrozincite in our study consisted of three samples. Concentrations of potential luminescent impurities are presented in Table 4.13. Laser-induced time-resolved technique enables to detect Pb center (Gaft et al. 2002a) (Fig. 4.85a, b). 

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It is interesting that yellow zircon luminescence is very specific and different from other Zr-bearing minerals such as catapleite, keldyshite, vlasovite, khibinskite and others, which are usually characterized by blue luminescence evidently connected with titanium impurity, namely TiOe complexes (Gaft et al. 1981). 

Pyrite, and other iron-bearing minerals such as hematite and llmonite, provide the iron that primarily is responsible for the colour of bricks. The presence of other constituents, notably calcium, magnesium or aluminium oxides, tends to reduce the colouring effect of iron oxide, whereas the presence of titanium oxide enhances it. High original carbonate content tends to produce yellow bricks. 

Aluminum is the third most abundant (7.5%) chemical element in the earth s crust. Aluminosilicate clay deposits are plentiful throughout the world. However, the extraction of aluminum from these deposits is not economically feasible. The principal aluminum ore in the world is bauxite, which usually represents a collection of different minerals such as gibbsite, diaspore, and boehmite. Also, other iron- and titanium-bearing minerals are many times found in bauxite. 

Rutile is formed primarily by the crystallization of magma with high titanium and low iron contents, or by the metamorphosis of titanium-bearing sediments or mag-matites. The rutile concentrations in primary rocks are not workable. Therefore, only sands in which rutile is accompanied by zircon and/or ilmenite and other heavy minerals can be regarded as reserves. The world reserves of rutile are estimated to... 

The above techniques have a wide array of applications, including those that are both analytical and physicochemical (such as bonding) in nature. Typical examples of research include the surface chemistry of ferrite minerals (38) and the valence states of copper in a wide array of copper (39) minerals. Other areas of bonding that have been studied include the oxidation state of vanadium (40) in vanadium-bearing aegirities (also using x-ray photoelectron spectroscopy) and the. surface features of titanium perovskites (41). ... 

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