Apophyllite occurs in irregular veinlets (about 3mm wide) which consist mostly of micro-crystalline (about 3μ long) of apophyllite itself, and cuts the associated wollastonite and marble, in a contact metamorphosed lenticular limestone of the palaeozoic age at Gobessho in Ôtsu City, Japan. It is associated with wollastonite, ferrosalite, vesuvianite, grossularite and marble. The hardness is 5, the specific gravity 2.42 (22°C), the luster vitreous, the color pale brownish, the refractive index 1.539±0.002, the chemical formula (K_0.77Na_0.13) (F_0.37OH_0.53) (Ca_3.74Mg_0.34)H_0.36(Al_0.36Si_7.60)O₂₀•8H₂O, and the space group D⁶_4h=P4/mmc.

View full abstract

Since 1921, Kozu, Endo, Hadding, Ito, and Chao and Taylor had investigated into the interlamination of constituent feldspars of moonstone by X-ray methods. It seems however that the problem of the modes of interlamination still defies satisfactory solution. The writers have discovered that moonstones from granitic pegmatites in Shiga Prefecture, Japan, have a new type of inter-lamination of four constituent feldspars. Of these feldspars, one is monoclinic potassium-rich and the remaining three triclinic sodium-rich, two of which are twinned after the albite law. All the (010) planes of the four constituent feldspars are parallel and all the c-axes of the three sodium-rich feldspars are identical in length, parallel in direction, and make an angle of 32′ to the c-axis of the potassium-rich one towards the a-axis of the latter.
This result shows that the interlamination of moonstones does not belong to one limited type, but is classified into such types as discovered by Ito, Taylor and the present writers.

View full abstract

Kilchoanite was synthesized by hydrothermal treatment from γ-dicalcium silicate-quartz mixtures in a temperature range of 160-600°C, though it was generally obtained at 600°C from other starting materials. The chemical formula of synthetic kilchoanite was 9CaO•6SiO₂•nH₂O (n=0.3-0.8), and its water content decreased with increasing temperature of the hydrothermal treatment. The X-ray diffraction pattern of the synthetic kilchoanite change neither with the water content, nor by the dehydration process until at 930°C when the conversion to rankinite took place. Kilchoanite was found to be metastable in all temperature ranges. The thermal behavior, density, and infrared spectra of synthetic kilchoanite were also studied.

View full abstract

Minerals of intermediate chemical composition between analcime and wairakite are described. They were found in the highest metamorphosed part of the laumontite and mix-layer chlorite zone of the metamorphosed area in the Tanzawa Mountains, central Japan. Chemical analyses and X-ray diffraction studies were carried out on these materials. The results plotted in the Wa-Nat-Ab′ diagram indicate that the compositional variation is more extensive than reported in the past. Possible distribution of vacant fields in the diagram is also discussed.

View full abstract

Interference colour of crystals were represented in the three dimensional Munsell system and the approximate ranges for various types of abnormal colour possibly produced by crystals were estimated. The range of colour appearance considerably depends upon the type of the abnormal colour series. It is noted that, when luminosity is low, the range for the centro- and non-cyclic types are confined in an area narrower than that for the chroma-cyclic type and the colour with a low value of chroma rarely appears in the former types.

View full abstract

A zeolite-like mineral was synthesized by reactions of clinoptilolite with NaOH solutions of varing normalities, below 100°C, within 1, 024 hours. It was determined as species-P, the mineral of harmotome-phillipsite group first synthesized by Barrer et al. (1959), according to X-ray powder patterns, differential thermal analysis, observations under the electron microscope and chemical analysis. The transformation of its crystal structure has been traced by X-ray powder methods as follows: clinoptilolite → species-P₁ (cubic) → species-P₂ (tetragonal). The results suggest a possibility of transformation from clinoptilolite into analcime which is one of the most important reactions in sedimentary rocks during diagenesis, since analcime has been synthesized from gels through species-P by Barrer et al. (1959).

View full abstract

A chabazite containing 1.40% of SrO was found in veinlets cutting a Permian basic albitized tuff on a limestone lens at Miyanohira, Ôme, Tokyo. It is optically biaxial negative with 2V=60°-70° ; α=1.489, γ=1.491, whereas the X-ray powder data are indexed with a hexagonal cell; a₀=13.77₉ Å and c₀=15.00₀ Å. The most probable source of strontium in this chabazite is a calcic plagioclase contained in the tuff before albitization, which released strontium as well as calcium and formed a sodic plagioclase.

View full abstract

The force fields controlling the structures of MgF₂, ZnF₂ and FeF₂ have been subjected to inspection in comparison with that in rutile previously dealt with. The force constants have been determined by the normal coordinate treatment on the basis of the modified Urey-Bradley force field, with the result that the calculated frequencies have been found well in accordance with the observed frequencies. It has been clarified that the ionic characters are to a certain extent reflected on the data obtained as to the interatomic force constants for the crystals in question. On the one hand, the nature of the bonds in, and the characteristics of, the rutile-type structures have been examined mainly with respect to the force field, and on the other, the elastic constants considered microscopically have been deduced from the force constants.

View full abstract

Beautiful green pyromorphite and yellow mimetite crystals were found from the Otaru-Matsukura barite mine, Hokkaido. The physical and chemical properties of these minerals were investigated. Pyromorphite, mimetite and intermediate solid solutions were synthetized, and their physical properties were compared with those of the natural minerals.

View full abstract

X-ray diffraction crystal-structure analysis of synthetic fluor-polylithionite, KAlLi₂Si₄O₁₀F₂, shows that this mica has a partially ordered octahedral cation distribution, with one site occupied by Li, and the other by Al_1/2Li_1/2, approximately. This ordering and distorted tetrahedra cause the surface oxygen ring to be nearly hexagonal, thus allowing polymorphs with 60° stacking rotation angles to occur. The apical Si-O distance is shorter than the basal Si-O, distances.

View full abstract

The mechanisms of the phase transformation among the three polymorphs of enstatite were investigated by heating experiments. Below 1, 000°C, clino-enstatite shows a tendency to realize in part the ortho-structure through partial disordering of the clino-structure. Well-ordered ortho-enstatite inverts itself into the proto-phase at 1, 150°C. When proto-enstatite is cooled from 1, 100°C at the rate of 100°C/hour, the phase persists down to 650°C, where it suddenly changes to disordered clino-enstatite with a remarkable shortening of the c axis. Possible structural mechanisms for the above transformations have been proposed. During the investigations mentioned above, it was concluded that β-MgSiO₃ with a=36.4 Å is, in all probability, identical with twinned clino-enstatite. The refinement of the crystal structure of proto-enstatite, which is stable above 985°C, was carried out with the intensity data obtained at 1, 100±6.5°C by high temperature precession technique, the residual R being 0.128 for 49 observed reflections.

View full abstract