Feldspar Glasses

As with ciystalline quartz, feldspar crystals also transform to diaplectic glass when, subjected to shock compression. Studies of diaplectic feldspar glasses have been carried out by many investigators using many techniques (TEM, X-ray, IR, and Raman spectroscopy, and thermal analysis [11,15,19,22,25,28-30,44-47] However, the 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. 

Small samples (spheres or cubes with size of about 0.5 mm) of diaplectic feldspar glasses (Table 3.1) were used for X-ray diffraction experiments [25,30,33]. The measurements of X-ray diffraction intensities were made using a four-circle 

Structural Evolution of Quartz and Feldspar and their Glasses 55 

We measured Raman spectra of diaplectic orthoclase glass obtained by experimental shock compression to 38 GPa [31]. The density of this glass is larger than that of orthoclase glass fused at 1650°C. Measured Raman spectra were corrected for the temperature and frequency dependence of first-order (Stokes) Raman scattering [52-55] using the correction relation (Fig. 3.7)  

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Table 3.1. Density and refractive index of some diaplectic feldspar glasses...

M. Okuno, T. Araki, Y. Syono, and B. Rcyaiu-d, Structural study of shock-induced K-feldspar glass. Special Issue of Rev. High Press. Sci. Tech. 8, p. 26 (1998). 

M. Taylor, and G.E. Brown, Structure of silicate mineral glasses. I. The feldspar glasses, NaTUSisOs, KTUSisOg, Ca7U2Si20g. Geochim. Cosmochim. Acta 43, pp. 61-77(1979). 

Structural Evolution of Silica and Feldspar Glasses by Shock Compression... 

D. Stoffler, and U. Homemann, Quartz and feldspar glasses produced by natural and experimental shock. Meteoritics 7, pp. 371-394 (1972). 

D. Heymarm and F. Horz, Raman spectroscopy and X-ray diffractometer studies of experimentally produced diaplectic feldspar glass. Phys. Chem. Mineral. 17,... 

Potassium feldspar glass (Type D). A glass-ceramic with a glass matrix similar to that of feldspar, K20 Al203 6Si02, can contain 10-20 wt% glass phase. 

Alkaline earth feldspar glass with excess Si02 (Types E and F). Thirty to fifty wt% of an aluminosilicate glass matrix of the 7 0 Al203 wSi02 type where R = Ca, Ba, Sr and n = 2 can be incorporated for alkaline earth feldspars. 

Table 1. Typical Feldspar, Glass, Mica, Amphibole, Pyroxene, Olivine, and Allophane Contents of Basalt and of the Subsoil of a Weakly Leached Red Loam, Papakauri Clay Loam from Basalt...

Feldspar, % Glass, % Mica, % Amphibole, Pyroxene, % % Olivine, % Allophane, %... 

Tables 2 and 3 show feldspar, glass, and allophane contents of New Zealand rhyolitic...

Table 2. Typical Feldspar, Glass, and Allophane Contents of New Zealand Rhyolitic Volcanic Ash and of a Young Yellow-brown Pumice Soil and an Older Yellow-brown Loam Derived from Rhyolitic Ash...

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