The structural change of gibbsite induced by dry grinding has been investigated by means of BET analysis, SEM observation, XRD, MAS/NMR spectroscopy and TG-DTA. The crystalline structure of gibbsite changes into a disordered one with the progress of grinding and subsequent RDF analysis of ground gibbsite samples suggests the structural variation in the local atomic arrangement around aluminum. MAS/NMR measurement also supports this change and indicates the formation of a tetra- and penta-coordinated aluminum at the expense of parent octahedral ones. Low temperature dehydroxylation reaction and new exothermic peaks at about 800 and 1000°C of ground samples were detected in TG-DTA.

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Bakerite has been found as a vein-forming mineral in crystalline limestone near gehlenite-spurrite skarns at Fuka, Okayama Prefecture. The wet chemical analysis, EPMA, and IMA of the mineral yield an empirical formula Ca_8.036B_9.963Si_6.033O_30.092(OH)_9.908 on the basis of O=40. The present data supports the chemical formula calculated by Palache et al. (1951) rather than that for natural specimens given by Giles (1903); Kramer and Allen (1956); Baysal and Dilekoz (1975). The DTA and TG curves, and IR spectrum are also measured. The optical and X-ray diffraction properties agree with previous data.
Bakerite from Fuka may be primarily formed under a low temperature hydrothermal condition.

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Polarized infrared absorbance spectra from the oriented plates of staurolite were examined for the orientation determination of OH⁻ dipoles in staurolite by a Fourier transform polarized infrared absorbance spectroscopy (pol-mFTIR). Seven polarized absorbance spectra observed in 3 μm region are due to the OH⁻ dipoles essentially existing in staurolite structure, and all of the corresponding OH⁻ dipoles are oriented parallel to the (010) plane. Three of the seven absorbance spectra are assigned to OH⁻ dipoles due to two sets of the OH bonds, P(1A)–O(1A) and P(1B)–O(1B), and P(2A)–O(1A) and P(2B)–O(1B), directly found by neutron diffraction studies. Unassigned four absorbance spectra indicate that additional hydrogen positions must be present in staurolite, and the unidentified hydrogen may be estimated to be a considerable quantity.

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The syntheses of zinc hydroxyl monophosphate Zn₂(OH)PO₄ were carried out under hydrothermal conditions of 573 K and 200 kg/cm². The crystal data are: orthorhombic, P2₁2₁2, a=8.099(1), =8.325(1) and c=5.966(1) Å. The structure was solved by three dimensional Patterson syntheses and refined by least squares methods to give a final residual index of R=0.042. There are four units of Zn₂(OH)PO₄ in a unit cell and three kinds of zinc atoms with different coordinations, where the first zinc atom is six-coordinated by four oxygen atoms and two hydroxyl groups, the second one is octahedrally coordinated by six oxygen atoms and the third one is five-coordinated by four oxygen atoms and one hydroxyl group forming distorted pyramids. The framework consists of infinite straight chains of Zn–O octahedra along c-axis, connected together by isolated PO₄ tetrahedra and distorted Zn–O pyramids. This compound is a polymorph of tarbuttite.

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