A suite of X-ray section topographs of a cube shaped diamond were taken around a Bragg condition of 220 at every 0.05 deg. rotation of reflection angle, θ. A four-circle diffractometer constructed for synchrotron radiation use was employed to take those photographs easily. The topographic pictures indicate that the cube-shaped diamond was consisted of two parts which were completely different in sub-microscopic texture. The inner part was composed of four growth sectors dividing the cube-shaped diamond along almost the diagonals, each of which was rotated by about 0.025 deg. relative to its neighbour. The outer part surrounding the inner part was highly mosaic and rather an accumulation of very small sub-grains which are around 800 Å in diameter and oriented almost coaxially with the inner part but in the range of about 0.8 deg.

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Stability of Mn-cummingtonite of nominal bulk composition Mg_4.65Mn_2.35Si₈–O₂₂(OH)₂ has been determined under hydrothermal conditions at 0.5, 1 and 1.5 kb (buffered by Mn₃O₄–MnO buffer) and at elevated pressure-temperature conditions using a piston-cylinder apparatus. The composition was so chosen as to closely correspond to the natural Mn-cummingtonites that occur in various hydrothermal and metamorphosed deposits of manganese in the world. Mn-cummingtonite is stable between 650°C and 675°C at 0.5, 1 and 1.5 kb and between approximately 580°C and 640°C at 3 kb. In this bulk composition, with increasing temperature talc + tephroite assemblage gives way to Mn-cummingtonite, Mn-cummingtonite + Mn-pyroxene + quartz and to Mn-pyroxene + quartz assemblages successively. The important conclusions arising out of this study are as follows. 1) Mn-cummingtonite is stable only upto 3 kb in the geologically feasible temperature range, while it coexists with Mn-pyroxene and quartz upto 5 kb, beyond which no hydrous phase is encountered. 2) The Mn-cummingtonite dehydration curve has a negative slope in P–T space. In natural occurrences, Mn-cummingtonite is associated with Mn-pyroxene, quartz with or without tephroite. The phase relationships brought about in this study can be applicable to natural occurrences.

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With a fluid pressure of 100 MPa, grandite garnets with various Fe/(Fe+Al) ratios have been synthesized hydro thermally from the mixtures of reagent grade of CaO, CaCO₃, Al₂O₃, Fe₂O₃ and SiO₂. Grossular is formed at the CO₂ mole fraction below 0.03, while the assemblage calcite-wollastonite-anorthite becomes stable above the value. An isobaric, isothermal eutectoid point appears in the system Ca₃Al₂Si₃O₁₂–Ca₃Fe₂Si₃O₁₂–CO₂. The point seems to be located approximately at 90 mole % in the andradite molecule, and 0.8 in the CO₂ mole fraction. This phase relation agrees with the fact that the composition of grandite from skarn-type ore deposits has a tendency towards andradite.

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