The short-range structures of NaGaSi₃O₈, NaAlGe₃O₈ and NaGaGe₃O₈ glasses, which have feldspar structures in crystalline phases, have been determined by X-ray diffraction and EXAFS spectroscopy techniques. The X-ray radial distribution functions showed coordination numbers of T atoms (T=Si,Al,Ge,Ga) in the glasses a little larger than four. Correspondingly, the T–O distances in NaAlGe₃O₈ and NaGaGe₃O₈ glasses obtained by X-ray radial distribution analyses are a little longer than those of NaAlGe₃O₈ and NaGaGe₃O₈ feldspars. The Ge–O and Ga–O distances of NaGaSi₃O₈, NaAlGe₃O₈ and NaGaGe₃O₈ glasses obtained by EXAFS spectroscopy are also a little longer than those in low-quartz type GeO₂ and in GaO₄ tetrahedra of β-Ga₂O₃, respectively. If the Si–O and Al–O distances are 1.61 and 1.75 Å respectively, the T–O distances obtained from EXAFS analyses are considered to agree with the values determined by X-ray radial distribution analyses. These results suggest that the structures of the glasses are essentially based on GeO₄ and GaO₄ tetrahedra and contain a small amount of GeO₆ and GaO₆ octahedra. The radial distribution functions of these glasses are well interpreted by model structures with cristobalite type linkages of GeO₄ and GaO₄ tetrahedra. The long range order diminishes from NaGaSi₃O₈, NaAlGe₃O₈ to NaGaGe₃O₈ glasses in this order. The densities of the glasses approach to those of the corresponding feldspar crystals in the same order.

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The relations among the IR absorption patterns, the cell dimensions, and the iron and water contents of the grossular–hydrogrossular series containing a small amount of andradite molecule, have been determined using hydrothermally synthesized products. The compositions of the prepared materials are written as Ca₃(Al_.95Fe_.05)₂(SiO₄)_3−x(O₄H₄)_x and Ca₃(Al_.9Fe_.1)₂(SiO₄)_3−x(O₄H₄)_x, where x=0, 0.2, 0.4, 0.6, 0.8 and 1.0. The cell dimension of garnet represented by the d₄₂₀ value increases with the increases of both of water and iron contents. On the contrary, the ratio of the logarithmic intensity of 3700 cm⁻¹ transmission band to that of 3660 cm⁻¹ absorption band decreases remarkably with the increase of water, while it is independent of the iron content. The transmission band near 700 cm⁻¹ shifts toward the high frequency side with the increase of water and the decrease of iron. The composition of garnet of this series can be estimated, therefore, on the basis of the IR absorption patterns and the X-ray powder diffraction data.

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Electrostatic energies of some olivines and orthopyroxenes, and the potentials of their octahedral sites were calculated by varying the charge of metal ions around the formal values. This calculation indicates that, in olivines, the larger M2 site is more ionic than the smaller M1 site, contrary to what is the case in orthopyroxens. This result is supported by the charge values recently determined by X-ray diffraction. These charge values also show that, in these minerals, the ionic charge is larger on Mg than on transition metal. The connection between the atomic charges and the electrostatic calculations gives insight to the ionic effect on the cation distributions in olivines and orthopyroxenes.

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