Saponite found at the Wakamatsu mine is a magnesium-rich member of the montmorillonite group. X-ray, differential thermal and chemical data of the mineral are presented. Influence of exchangeable Mg²⁺ ions on the X-ray diffraction pattern and the differential thermal diagram is discussed in some detail.

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Celadonite occurs as an alteration product of glass fragments in rhyolitic tuff at Oya, Tochigi Prefecture. The chemical composition: SiO₂, 55.99%; TiO₂, 0.49%; Al₂O₃, 11.13%; Fe₂O₃, 4.65%; FeO, 7.34%; MnO, 0.20%; MgO, 2.27%; CaO, 0.22%; Na₂O, 1.30%; K₂O, 8.00%; H₂O⁺, 4.22%; H₂0^-, 3.68%; total, 99.50%.
The structural formula:
(K_0.73Na_0.18Ca_0.02) (Mg_0.30Mn_0.01Fe²⁺_0.44Fe³⁺_0.25Al_0.93) (Si_3.99A1_0.01) O₁₀ (OH)₂.
Although the amounts of Al₂O₃ and FeO are slightly larger than in earlier data, the Oya specimen is identified to be celadonite from its mode of occurrence, X-ray powder pattern, i. r. absorption spectrum and DTA curve.

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Pentlandite, niccolite and gersdorffite from the Han Deresi and Günes districts, eastern Turkey, were described. The specific gravity and the cell constants of each of these specimens were measured, and it was confirmed that these physical data were in good agreement with those given in literatures. It was also concluded that the specimen of gersdorffite under investigation was of the ordered structure with the space group, P2₁3-T⁴. Chemical analyses of these specimens were carried out both by the usual wet method and with a electron microprobe. The results indicated that, when gersdorffite and niccolite co-exist, Sb seems to prefer entering into gersdorffite to going into niccolite. The stability field of gesdorffite was discussed and it was inferred that the presence of Fe in place of Ni might widen the stability field of the ordered form.

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Whiskers and needle crystals (prisms) of aluminum nitride (AlN) prepared by the sublimation method were found to grow through the so-called VLS mechanism. Their growth direction coincides with the c-axis. The starting material of AlN was decomposed into aluminum vapor and nitrogen above 2000°C and they were dissolved into a molten agent such as iron. Whiskers and prisms of AlN grew from the molten agent saturated with aluminum and nitrogen between 1550°C and 1700°C. Consequently most of the whiskers and prisms of AlN prepared by the sublimation method were crowned with a globe of such an agent as iron on the top.
Iron, cobalt and manganese are effective agents for the VLS growth mechanism of whiskers and prisms of AlN. Iron is the most effective and typical among them.
In the case of the VLS growth mechanism of AlN, the growth in the direction perpendicular to the c-axis scarcely takes place even after the main growth in the parallel to the c-axis have sufficiently developed.

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Ferrierite is a very rare mineral of the zeolite group. It was named and described in 1918 by Graham. A zeolite was collected at the Itomuka mine in Hokkaido, Japan, in 1953. A preliminary investigation revealed that this mineral was ferrierite. Ferrierite from this locality occurs mainly as spherical aggregates of radiating blades and as interstitial fillings in propylite. This ferrierite is found in association with calcite, barite, pyrite and especially closely connected with heulandite. It is white in color, with a vitreous luster, and up to 0.5mm in length. The first identification of this ferrierite was made by the X-ray powder method. Its Chemical composition was close to the result of Graham's analysis, though ours was poorer in Mg than Graham's. The chemical formula will be best represented by (Na_1.32K_1.57)Mg_1.09(Si_30.95Al_5.03Fe_0.01)_35.99O_72.01•18.82H₂O. The indices of refraction measured are α=1.483 β=1.484 γ=1.486 and the specific gravity is 2.06. Thermal properties of this ferrierite were studied by means of the derivatograph. Its DTA curve showed a large endothermic peak between 250°C and 260°C. A DTG curve revealed that its dehydration rate reaches a maximum of 0.85mg/min. at 260°C.

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Clinoenstatite from Papua was found to transform itself into a high-clino phase between 1, 050° and 1, 100°C. From its hOl precession photograph, a reasonable model of the structure was derived. Its probable space group is C2/c and lattice constants, a=9.93Å, b=8.79Å, c=5.34Å and β=110°15′. The SiO₃-chain in the structure is very similar in the projected configuration but reverse in the way of puckering to the chain (A) in clinoenstatite. Neglecting the slight difference in the shapes of SiO₃-chains, we can look upon the structures of high-clino and proto as built up of common unit slabs, whose arrangement according to gliding en echelon leads to the high-clino structure, and according to alternate gliding to the proto structure. The mechanism of transformations between the polymorphs of enstatite was also discussed in the light of the newly determined structure of high clinoenstatite.

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The authors proposed new elements of symmetry, the bisecting twin axis and the principal twin axis, to describe systematically the morphology of twin crystals. The bisecting twin axis is an axis that occurs within the twin plane and bisects a reentrant corner formed by the two individual crystals. The principal twin axis is an axis of symmetry perpendicular to the bisecting twin axis and to the twin plane; it comprises 6, 4, 3, ^-6, ^-4 and ^-3.
In an ideal form, with which two individual crystals involved in twinning have developed to an equal size, several bisecting twin axes exist on both sides of the reentrant corners which bound the two individuals; the arrangement of these axes corresponds to the symmetry of the principal twin axis perpendicular to the twin plane.
When a twin crystal is described by means of the bisecting twin axis, the principal twin axis and the twin plane, what has been heretofore defined as a composition plane would mostly turn out to be a twin plane. These newly proposed elements of symmetry would become an important basis for grouping the twinned point groups.

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In the present study, septechlorite-phlogopite equilibrium is examined in terms of temperature and pressure as well as the chemical composition of the starting solid materials and that of the solutions associated there-with. Data on variation in the composition of the septechlorite solid solution from penninite through sheridanite are also reported as functions of the above mentioned factors:
Where the pressure and bulk composition are kept constant, septechlorite progressively becomes more Al-rich with increasing temperature.
High Mg-ion concentration in the aqueous solution results in Al-poor septechlorite due to the cation exchange reaction of Mg²⁺ and H⁺.
The decreasing of the aqueous solution leads to septechlorite having a higher Al content.
Isobaric experiments show that as the ratio of KCl/MgCl₂ continuously decreased from 100:1 to 1:1, the equilibrium temperature progressively increased from 420°C to 530°C, and that the composition of the septechlorite in equilibrium with phlogopite changed with the equilibrium temperature. Elevated temperatures kept sheridanite in equilibrium with phlogopite, while progressively reduced temperatures brought about equilibrium between phlo-gopite and Al-poor septechlorite.

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Crystals upon transition or inversion often produce in their secondary phase a complicated twin which simulates a single crystal. The twinned crystal commonly consists of a super-structure based upon the primary form and the twinning is produced by the twin laws closely related to the symmetry of the primary form. Such a crystal shows a complex diffraction pattern, and it is generally difficult to distinguish the contribution by one individual from the others. An algebraic method for analysing these diffraction patterns through examination of the mode of distribution of satellite reflections is proposed and discussed in relation to the subsequent procedures such as structure determination and refinement.

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