Feldspars crystal structures

As in dissolution, a chemical and structural change can occur from hydrolysis as the ions replaced by or OH may be of a different size so that the crystal structure is stressed and weakened. An example of this is the weathering of feldspar or goethite by H ... 

Non-lattice sites may play an important role in the incorporation of large foreign ions in crystal structures during coprecipitation Pingitore (Chapter 27) discusses the importance of these sites in the formation of coprecipitates of calcium carbonate containing Srz+ or Ba. White and Yee (Chapter 28) discuss the diffusion of alkali ions into defect structures in the surfaces of glasses and crystalline feldspars. 

Bowen s reaction series representing the relationship of igneous silicate mineral composition to crystallization temperature. The plagioclase feldspars represent a continuous series grading from the calcium-rich to sodium-rich to potassium-rich forms. The rest of the minerals constitute a discontinuous series in which distinct crystal structures are characteristic of a particular temperature range under which the magma solidified. 

Gasperin M. (1971). Crystal structure of rubidium feldspar, RbAlSi30g. Acta Cryst., 627 854-855. 

Grundy H. D. and Ito J. (1974). The refinement of the crystal structure of a synthetic non-stoichiometric Sr-feldspar. Amer. Mineral, 68 1319-1326. 

Newnham R. E. and Megaw H. D. (1960). The crystal structure of celsian (barium feldspar). Acta Cryst., 13 303-312. 

The distinctly differentiated results obtained, for example, for different faces of quartz or feldspar crystal, with clear observed differences depending on structure and compactness of the material under test, are an argument for wide use of the Mackensen blower in the study of engineering properties of rocks and ceramic materials and also in hardness estimation of minerals. 

Structural Evolution of Quartz and Feldspar Crystals and their Glasses by Shock Compression... 

As with crystalline quartz, feldspar crystals also transform to diaplectic glass when, subjected to shock compression. Studies of diaplectic feldspar glasses liave been carried out by many investigators using many techniques (TEM, X-ray. IR, and Ramiui spectroscopy, and thermal analysis [11,15,19,22,25,28-30.44-47] However, tire number of atomic scale structural studies is limited [25,30,33,45]. In this section, our group s recent results on the structural analysis of some diaplectic feldspar glasses by X-ray and Raman spectroscopy will be presented, with comparison to many previously obtained data. 

An understanding of the mechanisms by which organosilicon compounds become attached to mineral substrates requires a knowledge of the crystal structure of the substrates examined. There is no doubting the presence of copious functional silanol groups (Fig. 10) on silicate material (quartz, feldspar, mica, clay) [2, 19-21], whose surface concentration on quartz fracture planes is... 

Smith JV, Brown WL (1988) Feldspar Minerals. 1. Crystal Structures, Physical, Chemical and Microtextnral Properties (2 Edition). Springer Verlag, Berhn, 828 p Smith JV, Steele IM (1984) Chemical substitution in sihca polymorphs. Neues Jahrb Mineral Mon 3 137-144... 

Wilkins and Sabine (1973) used IR spectroscopy to determine water contents of kyanite, andalusite, sillimanite, grossular, andradite, pyrope, diopside, olivine, and feldspars. They found low water contents 0.008 wt.% in olivine, 0.02 wt.% in diopside, and 0.009 wt.% in pyrope. Zemann, Beran, and co-workers published a series of papers on IR spectroscopy of both hydrous minerals and NAMs (e.g., Tillmanns and Zemann, 1965 Beran and Zemann, 1971, 1986 Beran, 1971, 1986, 1987 Beran and Gotzinger, 1987 Beran et al., 1993). For the most part, these contributions were focused on the substitutional mechanisms by which hydrogen entered the crystal structure, rather than on the absolute amount of hydrogen in the crystal structure. 

The crystal structures of the synthetic feldspars SrGa2Si20g and BaGa2Si20g are both similar to that of celsian. There is complete Ga-Si ordering in the former, and probably in the latter also. ... 

Scapolite has a complicated crystal structure and is formed by the alteration of plagioclase feldspars. Incidentally, diamond, sapphire, and ruby all fluoresce, but as with the materials above, the color depends on the UV wavelength used. A given specimen can also show different colors depending on the distribution of impurities. Trace elements can be included in synthetic gemstones to make them fluoresce and thus be easily identifiable. 

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