Crystallization of the Glasses in the Li2O-SiO2 System

Heterogeneity of the Li2O—SiO2 glass and the process of crystallization through heating were investigated by using the electron- and ordinary microscopic techniques. Under the electron microscope the separated droplet phases of about 100 Å in diameter were observed comprised in the matrix of the opales-cent glass composed of lithium trisilicate, while the parts of the colorless and transparent glass of lithium disilicate were also found to be slightly heterogeneous. In addition to above, the fact that the interfacial boundaries between two separated phases are not favorable for nucleation of the crystals was also confirmed. As a result of the differential thermal analysis, a small-scaled endothermic phenomenon assumed to be necessary for the atomic rearrangement was recognized just before the remarkable exothermic reaction ascribed to crystallization. Moreover, it is to be noted that devitrification of the glass rod accompanied with crystallization of lithium silicate and lithium metasilicate was markedly promoted in a short period of about two months

9 Å Mineral Included in the Weathered Biotite

A mineral species revealing the basal reflection at about 9 Å was found in some flakes of the altered biotite collected from the weathered granite cropping out in the vicinity of Hiroshima City and mineralogically investigated in detail

Alteration of Plagioclase in Granite during Weathering

Secondary minerals of plagioclase in spheroidally weathered granite of the Seranishi-cho, Hiroshima Prefecture, Japan have been examined by the technique of X-ray diffraction, X-ray fluorescence, DTA, TGA, pH measurements and electron microscopic observation. Spheroidally zoning of A, B and C owing to the difference of appearance at outcrop corresponds to the secondary mineral components, that is, allophane or allophane-like substance is found only in the zone C of core-part of granite and the zone B, metahalloysite and halloysite are predominant in the zones A and B that were intensely weathered parts, and kaolinite exists in the zones A and B, but lacks in the zone C. The crystallinity and grain-size of these kaolin minerals increase gradually from near central core-part toward the outer A zone. The probable al-terating sequence of plagioclase in the weathered granite of this district has been roughly assumed as follows: [Original table is skipped. For more details, please refer to the full text.

Thermal Studies of Some Minerals, No. 3.: On Thermal Transformation of Antigorite in Air

The pulverized specimens of antigorite were subjected to the thermal treatments at various temperatures up to 1000°C in the air, and the effects of dehydration together with recrystallization were pursued by means of DTA, TGA, X-ray diffraction, infrared absorption spectroscopy and electron microscopy. The results obtained evidently suggest that emergence of the shoulder-like endothermic and exothermic peakes on the DTA curve is ascribed to destruction of the super-lattice structure of the original antigorite and production of the "mosaic olivine" during dehydration respectively and that under electron microscopic observation the recrystallized olivines with various shapes showing the specific relationships to orientation of the original mineral, controlled by the position, are discernible

Effect of Transition Elements upon the Nucleation and the Morphology of Magnetite in Silicate Melts of Basaltic Composition

Effects of transition elements, Ti, Cr and Cu upon the nucleation and morphology of mag-netite in silicate melts of basaltic compositon were examined. Crystallization of magnetite was carried out at △T= — 10°C in the atmospheric condition. Quenched products are composed of magnetite, (plagi-oclase) and silicate glass. Examinations of the morphology of magnetite show that an addition of Ti and Cu with Keff 1, has a definite effect to decrease grain size and to increase the number of crystals. The results obtained were discussed in relation to σ*, σ** and Keff

Landform and Weathering of the Chugoku Mountainous Region (Japan)

Chugoku District is characterized by gently undulated mountains in which three flatland levels are differentiated. The largest flatland level, the so called "Kibi Highland Level", is a presumed elevated peneplain. Deep weathering of different kinds of rocks and sediments in Chugoku District, which has been noted for many years, was found to be tightly associated with the flatland levels

Sr_2MgSi_2O_7:Eu ケイコウタイ ノ ゴウセイ ト ケイコウ トクセイ

Sr-akermanite ((Sr_Eu_x)_2MgSi_2O_7(x=0～1.0)) activated by Eu has been prepared by solid-state reaction at 1330℃ in an air atmosphere and its luminescence properties were studied. Sr-akermanite (x=O.05～0.6) shows a blue emission whose park is near 466nm under long-wavelength ultraviolet light excitation (366nm). Sr-akermanite (x=0.01) has the strongest emission intensity. It is found that Eu^ substitute in Sr^ site of Sr-akermanite fired under an air atmosphere

オケルマナイト ハーディストナイトケイ コヨウタイ ノ ゴウセイ

Studies on formation, thermal reaction and lattice dimensions of solid solutions in the system akermanite (Ca_2MgSi_2O_7)-hardystonite (Ca_2ZnSi_2O_7) have been carried out by DTA and X-ray powder diffraction on the products which were prepared by solid-state reaction using CaCO_3,MgO, ZnO and SiO_2 as starting materials. Åkermanite and hardystonite were preferably synthesized with double heatings at 1,330℃ and 1,250℃, respectively. The solid solutions were done at the intermediate temperatures in proportion to Mg/Zn of solid solutions. From akermanite to hardystonite, the melting points changed from 1,462℃ to 1,432℃ with approximately linear line. Further, the unit tetragonal cell constants, a_0 and c_0,changed linearly from 7.8328 and 5.0081 (Å) to 7.8250 and 5.0166 (Å), respectively. It is concluded that the solid solutions in the system akermanite-hardystonite form a complete series of solid solution by isomorphous replacement of Mg by Zn