Neodymium pentaphosphate (NdP₅O₁₄) crystals are grown by the flux method. The crystals obtained are 3 to 7 mm in diameter and 1 to 3 mm in thickness.
Lattice parameters are a₀=13.012±0.008Å, b₀=8.967±0.006Å, c₀=8.756±0.005Å, β=90.56±0.02° and the space group is P2₁⁄a. The orientation of the optic elastic axes referred to the crystal axes for D(5893Å) line is as follows; Y∧c=8.2°, X=b, Z∧a=7.7°, 2V=(+)64.0±2°. Refractive indices for D-line are α=1.609, β=1.613, γ=1.629. Twin planes (100) and (001) are observed in NdP₅O₁₄ under the polarizing microscope between crossed nicols. The twin boundaries migrate by an external stress along the [-101] and [10-1] directions.
When the temperature is raised, they disappear at 149±1°C and the extinction angle (c∧Y) becomes 0°. This phase transition is of the thermodynamically second order. According to the Aizu theory, NdP₅O₁₄ crystals belong to the mmm1′F2⁄m1′ species.

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The phase relation in the pseudobinary system Fe₂SiO₄–FeAl₂O₄ has been studied under the conditions up to 100 kbar and to 1300°C. The reaction of Fe₂SiO₄ (fayalite) and FeAl₂O₄ (hercynite) to Fe₃Al₂Si₃O₁₂ (almandine) and FeO (wustite) was clarified to occur above 25 kbar at 1000°C.
Preliminary experiments in the system Co₂SiO₄–CoAl₂O₄ have also been performed and a similar reaction, 3Co₂SiO₄+CoAl₂O_4←^→4CoO+Co₃Al₂Si₃O₁₂, was found to occur.
It is suggested that another similar reaction, 3Mg₂SiO₄+MgAl₂O_4←^→4MgO+Mg₃Al₂Si₃O₁₂, may occur in the system Mg₂SiO₄–MgAl₂O₄ and that there is no possibility of complete solid solubility between aluminate spinel and silicate spinel.

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Cell dimensions of ajoite have been determined using electron and X-ray diffraction data: a=15.218(8), b=24.712(14), c=13.632(12) Å, β=92.91(6)°, V=5118(6) ų. Space group: P2₁⁄m or P2₁.

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The crystal structure of rankinite (Ca₃Si₂O₇) was refined to an R value of 0.033 by full matrix least-squares using 1492 three-dimensional counter-measured intensity data. The crystal is monoclinic, P2₁⁄a, with a=10.557(1) Å, b=8.885(3) Å, c=7.858(1) Å, β=119.586(6)°, Z=4. The coordination polyhedra of calcium atoms form sheeets parallel to the (010) plane, between which Si₂O₇ groups are inserted. The lengths of Si–O bridge bonds are longer than those of non-bridge bonds. Listings are given of newly obtained bond lengths and bond angles of the structures.

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