We have installed a new furnace equipped with a rotational viscometer for use in viscometry at high temperature (one atmosphere) under controlled oxygen fugacities. This furnace allows sampling at the time of the viscosity measurement. Utilizing this furnace, we examined the relationship between textural parameters (crystallinity and the apparent aspect ratio of crystals) and viscosity during cooling of a basaltic magma. The 1707 basalt from Fuji volcano was used for the experiment and the result shows a drastic increase in viscosity from the liquidus temperature (1230°C; η = 52 Pa s), through 1170°C (crystallinity = 11%; η = 350 Pa s), to 1130°C (crystallinity = 23%; η = 1950 Pa s). The increase in viscosity during cooling is affected by both the increase of the crystallinity and the change of melt composition as a result of crystallization. For the basalt from Fuji volcano, crystallization of thin tabular plagioclase enhanced the strong effect of crystal entanglement, whereas the changes of melt compositions did not affect the viscosity because of the increase of ferromagnesian components and the decrease of feldspathic component in the residual liquid during crystallization. The effect of the presence of crystals on the viscosity is much larger than that expected from the Einstein-Roscoe equation with Marsh's constant (η = η₀ (1 − φ/0.6)^−2.5), where denotes the crystal fraction. The additional correction of Simha on the solid shape parameter slightly overestimates the increase in relative viscosity in the presence of thin platy crystals. A shear rate dependence of the viscosity was observed at lower temperature crystal-rich conditions.

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Phengites in the Piemonte calcschists from the western Alps, Italy were examined using an electron micro probe analyzer (EMP). The EMP analyses revealed that the phengites in five samples show variable Si/Al and Na/K ratios within a single thin section and even within individual crystals. Their interlayer cation content is less than 1.0 pfu (K + Na + Ca + Ba = 0.82-0.95 for O = 11), although most paragonites in these samples have values of 1.0. Their chemical compositions plot in the region above an ideal Tschermak substitution line on an Si-Al diagram even though paragonite compositional data invariably lie close to this line. The cation balance indicates that the interlayer cation vacancies are due not only due to K₁Al₁ − [ ]₋₁Si₋₁ substitution (pyrophyllite component) but also to a deficiency in alkaline elements. The charge balance in the crystals should be buffered by ions such as H₃O⁺, NH₄⁺ or Fe³⁺ that can not be detected by EMP. Large flakes of phengite (ca. 0.3 mm × 0.6 mm) are observed in one of five samples. A back-scattered electron image indicates that brittle deformation of these large crystals took place and was associated with formation of secondary low-Si and high-Na phengites, which overgrow the rim and fill crack of high-Si phengite. This strongly suggests that the vacancies developed during the Alpine HP metamorphism and were preserved during the retrograde metamorphism accompanying the ductile and brittle deformation.

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Phlogopite was found in small amounts in the contact-metamorphic aureole of the dunite-harzburgite complex at Yanomine. Phlogopite occurs intimately associated with hydrous silicate minerals such as serpentine and chlorite in the olivine-orthopyroxene metamorphic zone. The mineral also occurs as inclusions together with serpentine in chromian spinel grains of chromitite bands in dunite. The former interstitial phlogopites, characterized by lower TiO₂ and Na₂O contents compared with the latter included phlogopites, are suggested to have formed by a metasomatic reaction with fluids infiltrated into the rocks through cracks from the intruded granitic body in the stage later than the peak of the contact metamorphism. Prolonged infiltration of fluids changed some of the phlogopites to phlogopite hydrates. The latter included phlogopites probably crystallized from an incompatible elements-enriched hydrous melt generated by mantle-melt interaction, and were later hydrated during serpentinization.

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Silicate precursor gels containing Ni ions were prepared from sodium metasilicate and nickel nitrate solutions by geopolymerization at room temperature. Caustic soda solution was introduced as pH stabilizer. The gels obtained were heat-treated at 700-1400°C for 1 hour. Crystalline phases as well as raw gels were characterized by XRF, TG-DTA, XRD and FE-SEM techniques. NiO contents of the gels increased with increasing pH values. Gels having stoichiometric composition of liebenbergite, Ni₂SiO₄ were obtained at pH 12.8 with slight Na₂O contamination. Na₂O contents of the gels also increased gradually with increasing pH values up to 5.87% at pH 12.1 and finally decreased abruptly down to 1.5-2% levels, when exceeding pH 12.6. This trend was very convenient to obtain stoichiometric liebenbergite gels having less Na₂O contamination. Two categories of gels were found by TG-DTA in respect to exothermic peaks. Gels prepared at low pH region, ca. 0-5, and high pH region, ca. 13-14, showed no exothermic peaks, indicating that the gels were composed of not inorganic polymers but of simple aggregates of coprecipitates. On the contrary, gels prepared at intermediate pH region, ca. 5-13, showed a sharp exothermic peak, indicating that the gels were composed of inorganic polymers in which atomic order mixing took place due to polycondensation of metal-bearing silica complexes. Accordingly, crystallization temperatures of the gels were lower for the latter that was around 800°C than for the former that was around 1100°C. When heating the gels at elevated temperature, liebenbergite precipitations were observed almost in all gels associated with cristobalite and/or bunsenite according to pH values of gel preparation. The crystalline phases were in nanometer order in size, generally less than 70 nm. The obtained liebenbergite crystallites were platy flakes and 2-dimensionally developed in morphology.

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