Monoclinic and tetragonal (Zr, Ti)O₂ solid solutions coexist stably with rutile at 1, 080°C. There is a very large difference in the partition of the TiO₂ component between tetragonal and monoclinic solid solutions. The small solubility of TiO₂ component in the monoclinic modification is explained by the distorted crystal structure.

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Single crystals of ZrO₂ in tetragonal crystal forms were synthesized by flux methods. The tetragonal crystal was transformed into a single or twinned monoclinic phase during cooling. The observed orientational relations between the two phases is c_t//c_m, and {100}_m//{100}_t. Three kinds of orientational relations were observed on heating transformation; c_t is parallel to c_m, b_m, and a_m^*. The equilibrium temperature of the monoclinic and the tetragonal phases is 1, 145±10°C.

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Muscovite heated in molten KCl at 900°C to 1, 100°C was studied by means of X-ray analysis, optical and electron microscopy. The mineral newly formed by this treatment was identified to be kaliophilite from X-ray powder data. Crystals of the kaliophilite are acicular in form and are aligned in two directions at 120° on muscovite with the topotaxial relations: pseudo b_mus//c_kalio, pseudo a_mus//a_kalio and [001]_mus//[1^-100]_kalio. These relations suggest that oxygen layers of muscovite, which are perpendicular to the tetrahedral sheet and include pseudo a-axes are inherited to the structure of synthetic kaliophilite, while the oxygen plane (001) in muscovite is not. The kaliophilite gives a diffraction pattern consisting alternately of rows of spots and lines perpendicular to c^*, suggesting that the synthetic kaliophilite has statistical displacements in (100). The structure with ordered displacements will be that of natural kaliophilite.

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The vacuum evaporation method has been applied for preparation of low-temperature phases of iron sulfides. Thin films were synthesized from natural pyrrhotite crystals on cleaved halite crystals heated at different temperatures. The films have been identified by the electron diffraction method to be greigite, Fe₃S₄. Presence of a small amount of marcasite has been also confirmed in the films prepared on halite crystals at room temperature.

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X-ray and infrared studies have been made on synthetic materials prepared hydrothermally at 300-660°C and 18, 000-38, 000 psi from gels with compositions ranging from pennine to amesite. The results indicate that the solid solution range of the chlorite phase does not extend to the amesite composition in the present experimental conditions; the range is almost identical or slightly extended to the Al-rich side compared with that of natural well-crystallized Mg-chlorites. The polytype of the synthetic Mg-chlorite is IIb, which exhibits regular stacking in the high aluminum materials. The differences in cell dimensions and OH bands between the synthetic and natural chlorites suggest a difference in the distribution of cations within the talc and brucite octahedral layers. An even distribution of the octahedral cations is inferred for the synthetic chlorite, which is regarded as a high temperature form. The latter conclusion is supported by a hydrothermal treatment of natural chlorite. Additional information on the polytypes of the serpentine phase is also presented.

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The phase diagram of the PbF₂-ZrO₂ system is refined. In the growth process of ZrO₂ crystals in the PbF₂ flux, the compositional changes during the evaporation of the flux are measured by the thermal balance method in the slow cooling and the vaporization techniques, and the most suitable condition for the growth is discussed. Morphological aspects and surface features of Zr0₂ crystals in various growth stages are also described.

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A new type of silicon carbide consisting of 45 layers was formed in high silicon vapour atmosphere at 2, 300°C. The structure of this polytype was determined with the aid of a simple assumption newly introduced; SiC polytypes belonging to high temperature phases will not have in their layer sequences such an element as represented by the Zhdanov symbol 1. The structure of this polytype thus derived is represented as (332232)₃. The validity of the above assumption is discussed.

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