Two dimensional lattice images of dioctahedral mica with the projection along a_1M, [110]_2M or a_3T-axes were obtained for wedge shaped non-curled edges of sericite crystals. Stacking sequences representing 1M, 2M and 3T polytypes are observed within a small area of the crystal. The lattice images show one-to-one correspondence to the crystal structures of these polytypes. It is interpreted that octahedral vacancies appear as white spots in these lattice images.

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The recovery process from rounded to faceted morphology of NaClO₃ crystals has been observed in situ using a specially designed cell which can be used with temperature control of 1/100°C. A seed crystal is dissolved at first to a rounded form, and then by changing temperature of the solution to growth temperature, the process of recovery is observed. In the initial stage of growth, {100}, {110} and {111} develop as flat faces with their centres depressed. As recovery proceeds, {110} and {111} faces are gradually replaced by the {100} faces. The regions of the rounded surface whose tangents are indexed as higher indices are recovered by the kinematic steps from the neighbouring flat faces such as {100}. Crystals eventually become cubic bounded by {100} faces alone. Growth rates in the directions perpendicular to (010), (140), (120) and (110) were measured to establish the basis for further studies on growth mechanism from solution phase.

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Normal growth rates of {100} faces of NaClO₃ and KBr crystals in aqueous solutions have been measured under relatively high supersaturation regions, using a specially designed cell for in-situ observation. The growth rates versus supersaturation relations are examined in order to investigate the growth mechanisms, based on BCF and two dimensional nucleation growth theories. As the most plausible growth mechanism, the birth and spread model in two dimensional nucleation growth theory is suggested for both crystals in the supersaturation ranges investigated. Based on this mechanism, the growth rate constant A and relative edge free energy γ′⁄kT are calculated to be in the order of 4×10⁻⁴ cm/sec and 0.2 for NaClO₃, and 3×10⁻³ cm/sec and 0.2 for KBr, respectively. These values are reasonable in comparison with the values for other ionic compounds. The growth mechanism of NaClO₃ and KBr in aqueous solutions from low to high supersaturation ranges is also discussed, based on the present results and the previously published data, which lead to a conclusion that BCF mechanism is applicable under the low supersaturation region, whereas two dimensional nucleation growth will predominate up to the supersaturation range where dendritic growth occurs.

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A 7T wollastonite was found at Fuka, Okayama Prefecture. Based on film intensity data, its stacking sequence has been found as (TTGTGTG). Here, T represents a (100) slab of wollastonite which is in continuous position with respect to the preceding one, and G a slab displaced by b⁄2. The structure may be regarded as a mixed-layer structure composed of three 2M and one 1T. The structure gave R=0.13 for 65 hk0 reflexions observed. The lattice constants are a=54.3±0.3 Å, b=7.30±0.03 Å, c=7.08±0.03 Å, α=90.0±0.2°, β=95.5±0.2°, and γ=92.1±0.2°.

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The 3R-type modification of molybdenite was found as the first occurrence in Japan by means of X-ray powder diffraction method. Three examples are described here: (1) products of fumarolic activity on the Satsuma-Iwo-jima, southern Kyushu, (2) samples in high temperature hydrothermal wolframite-bearing quartz veins of the Yamate (Shitekurayama) mine, Okayama Prefecture, and (3) those in contact metasomatic molybdenum deposits of the Okawame mine, Iwate Prefecture. All the specimens examined are admixture of the 3R and 2H₁ polytypes with varying ratios.

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