Disorder of the metal atoms in the cubic cubanite, CuFe₂S₃, Z=4⁄3, obtained by heating orthorhombic cubanite from Ohmine Mine at 300°C for 2 hours and quenched, is investigated by X-rays at room temperature. The cubic cubanite has the sphalerite-type structure with disordered arrangement of the Cu and Fe atoms in the tetrahedral interstices of sulfur atoms of cubic closest packing. The residual electron density around the metal sites in the difference synthesis indicates displacement of some of the metal atoms from the centers of the tetrahedra or anharmonic thermal motion in the tetrahedral sites. For a statistical split atom model, some (∼6%) of metal atoms are displaced toward the four centers of sulfur triangles. The least-squares refinement of anharmonic thermal motion gives the third-order parameter of c₁₂₃=0.00027(21).

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The system KMg_2.5Ge₄O₁₀F₂–KMg₃Ge₃AlO₁₀F₂ forms a complete solid solution. The analyzed specimen has a structure of the 1 M mica with cell dimensions of a=5.413(1), b=9.368(2), c=10.531(6)Å and β=99.88(5)° and the experimental composition of KMg_2.64Ge_3.72Al_0.28O₁₀F₂. The structure was refined with the full-matrix least-squares procedure to the final R value of 0.042 for 1568 observed reflections. The structural features are the intermediate between the two opposite end members. The Mg²⁺ ions and vacancies are partially ordered in two independent octahedral sites. The distortion of the (Ge, Al)O₄ tetrahedra has been discussed in comparison with that of the (Si, Al)O₄ in silicate micas.

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A high-temperature single crystal X-ray diffraction camera has been constructed by modifying an infrared thermal-image furnace. High temperatures (∼1700°C) can be readily attained by focussing radiation from a halogen lamp on a single crystal with a gold-plated internal ellipsoidal reflector. This camera has been used for examining the phase transformation and melting of orthopyroxene and proved to be useful for the study of the phase changes and the structure states of the produced phases in single crystals at high temperatures.

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Synthesis of a manganoan fluoromica KMg₃(Si_3.5Mn_0.5)O₁₀F₂ with Mn in fourfold coordination was tried, utilizing mixtures of KF, MgF₂, MgO, SiO₂ and MnC₂O₄ for the starting materials. Mica crystals were obtained below 1150°C after crystallization of manganoan chondrodite (Mg, Mn)₅Si₂O₈(OH, F)₂. The X-ray structure analysis revealed that the crystal has a structure of the 1 M mica with cell dimensions of a=5.285(1), b=9.157(1), c=10.190(2)Å and β=99.97(2)°, and a chemical composition corresponding to K(Mg_2.44Mn_0.24)(Si_3.82Mn_0.18)O₁₀F₂. The structure refinement was carried out with the full-matrix least-squares procedure to the final R value of 0.043 for 1131 observed reflections. The (Si, Mn)–O_apical distance is 1.616Å and the mean (Si, Mn)–O_basal distance is 1.638Å. The mean (Si, Mn)–O distance of 1.632Å is longer than the literature value of 1.625Å for the mean Si–O distance in the SiO₄ tetrahedra by 0.007Å, supporting the conclusion that Mn atoms substituted a part of Si⁴⁺ ions at the tetrahedral sites in the present experiment. The mean octahedral cation-anion distances are 2.071Å for M(1) octahedra and 2.070Å for M(2). The tetrahedral rotation angle is 1.73°, and the octahedral flattening angles are 58.4° for M(1) octahedra and 58.3° for M(2).

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