The authors studied the mechanism of twinning of calcite, chabazite and fluorite that occur as penetration twins. In the past, the interrelations of individual crystals of these twins were usually explained by the 180° rotation on the twin axis [0001] or [111]. Using an ideal form, in which the two individuals participating in the twin were develped into an equal size, the authors examined the symmetry axis which exists on the twin plane perpendicular to the two-fold rotation axis. It was ascertained that this plane had three two-fold symmetry axis intersecting each other at an angle of 120°, that is, the two-fold symmetry axes occur at an interval of 60°. Accordingly, the authors decided to describe these twins as the ones having six-fold symmetry axes as their principal axes, and proposed to call them hexagonal birhomb ohedron twin and hexagonal bicube twin, respectively.

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Petrographical and chemical studies have been made on basaltic rocks of the northern part of the Nishisonogi peninsula, Nagasaki prefecture.
In these basaltic rocks following three groups are distinguished that is (1) Tholeiitic basalts, (2) Calc-akali basalts or andesites and (3) Alkali basalts in ascending order. Most of their chemical compositions vary in SiO₂ content from 47 to 53 weight percent.
These basaltic rocks are slightly higher in FeO+Fe₂O₃, and slightly lower in TiO₂ and P₂O₅ contents than basaltic rocks of the adjacent areas.
High-alumina basalts and high-alkali tholeiitic basalts of (1) are present in the same geological horizon and are concidered to be correlative with each other.
It is considered that calc-alkali basalts in lower volcanic rocks are derived from tholeiitic basalt magma, however calc-alkali basalts in upper volcanic rocks are derived from alkali basalt magma. The former is lower in K₂O and in Na₂O contents than the latter. Those two groups above mentioned are well distinguished in SiO₂-K₂O diagram.

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トロイライトは,Fe:S=1:1組成の低温型硫化鉱物で,地球上での産出は,非常に稀であるが,隕石中には,広く見出されている。筆者は,鉄隕石(Canyon Diablo, Odessa, Sardis)から,トロイライトを取出し, X線回折,メスバウアースペクトルの測定を行った。X線回折では,粉未線のd(1124)は,2.093→で,定比組成のFeSであった。単結晶X線回折からは,a=√₃A=5.97→ c=2C=11.75→の六方晶系で, 2C型の超格子構造を示している。Fe⁵⁷のメスバウアー効果から,アイソマーシフト,四重極相互作用,内部磁場を測定した。スペクトルは,強度比が,ほぼ3:2:1:1:2:3の吸収を示し,線巾は,合成FeSに比較して著じるしく狭く,定比組成からのずれは,極めてわずかである事を示している。

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The clayey or garnular specimens of deweylite and poorlycrystallized serpentine found from Wakamiya-cho, Fukuoka Prefecture, occuring as fine veins, have indicated the following chemical formulae respectively:
3.6 MgO•3 SiO₂•5.6 H₂O••••(Y 43),
3.9 MgO•3 SiO₂•5.7 H₂O••••(Y 50_b),
3.7 MgO•3 SiO₂•5.3 H₂O••••(Y 51),
2.9 MgO•2 SiO₂•1.9 H₂O••••(Y 40).
The chemical formulae of the first three specimens are close to the standard formula of deweylite and the last one to that of serpentine.
These specimens have given the very similar X-ray powder patterns one another, but the slight differences have been recognized in intensities of the first three diffraction peaks. And no marked structural differences were indicated on the heat treatment between the two mineral species. On the differential thermal analysis curves, some features were recognized: deweylite showed a large, dual endothermic reaction with a remarkable peak at 100 to 200°C and being immediately followed by a small shoulder at about 250 to 300°C, and it showed no plain endothermic reaction at about 700 to 800°C, however, poorly crystallized serpentine did a sharp reaction in the same temperature region. The particle shapes of these minerals are also close, showing generally rounded shapes with polygonal or irregular outlines. Deweylite would readily appear to be fluffy or take rounded forms with fine projections, however, poorly-crystallized serpentine would rather take angular forms.

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