Spherulitic rhodochrosites have been found in the bedded manganese ores in the Chichibu belt, Japan. They appear in a layered texture and each crystal has needle-like shape of submicron long. It shows clear extinction cross under nicols. Syntheses of the spherulitic rhodochrosites were made successefully in silica gels . The silica gels containing carbon dioxide ions were prepared in a test-tube at room temperature. The upper portion of the test-tube was then filled with manganese chloride solution. After one month, the manganese ions diffused completely and the rhythmic layered texture, Liesegang ring, appeared in the silica gels. The precipitated rhodochrosites in each of layer form sphrulites which show the same cross extinction under microscope as that of the natural specimen. As a result of the experiments, it is concluded that the natural spherulitic rhodochrosite ores with the layer texture are formed by the diffusion process in gels.

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This paper describes released gas analysis of manganese wad from Akan, Kogane and Niimi. The samples were heated by the infrared image furnace in He gas condition, and mass spectra of released gas phase were measured by Q-mass spectrometer. Experimental results show that(a) the detected phases on heating are H₂O, N₂, O₂ and CO₂, (b) the volume of CO₂ mainly depends on the species of manganese mineral, and(c) O/Mn ratio of manganese wad was varied widely and there is a negative correlation between O/Mn ratio and crystallinity. The above features are mostly depend on the amorphous part of the managanese wad. As X-ray diffraction method is insufficient for amorphous phase, gas analysis can provides an important data for study of manganese wad. Manganese wad from Akan (Akan-2) shows unique charactaristics.(a) Akan-2 does not release O₂ gas on heating in He gas condition.(b) The structure deforms on heating at 42°C.(c) The DTA data shows a exothermic peak at 300°C.

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The Urizukuri area of Abu county is underlain by the middle Permian Kyôdoko formation, composed mainly of chert including limestone pebbles and blocks. The formation is intruded by quartz-porphyry dyke of Cretaceous age, and suffered thermal metamorphism and later hydrothermal alteration. The rocks are recrystallized into quartzite, marble and skarns. Wollastonite, garnet, clinopyroxene, actinolite, vesuvianite, epidote and others were formed by the skarnization, occasionally associated with ore minerals such as magnetite, pyrrhotite, pyrite, chalcopyrite, sphalerite and galena. Apophyllite, laumontite, malachite, goethite, clay minerals and opaline silica occur as the hydrothermal products. Massive ore deposit consisting mainly of todorokite and several manganese dioxide minerals are embedded in chert near the dyke of quartz-porphyry, and total amounts of the deposit attain about 200 tons. Banded structures are seen in the deposit, made up of cyclic thin beds of cryptomelane, todorokite, birnessite, psilomelane, pyrolusite intercalating limonite and clay layers. Wet materials of the todorokite enrichments have soft and sticky appearances with coal-black color, and dry materials are loose with brown color. Manganese minerals, also, disseminate along joints or minor faults in the country rocks. In this case, however, the manganese minerals are poorly crystallized and nearly non-crystalline. Under the electron microscope, todorokites are platy to columnar crystals of 2-3 μm in diameter with a set of perfect cleavages. The lattice parameter of the dry material somewhat decreases than the wet one. The d-spacing of the strongest diffraction of the dry material somewhat decreases than the wet one. The mineral characterized by endothermic peaks of 120°C, 670°C and 980°C on their differential thermal analysis curves. From the occurrences and mineralogical data, it is considered that the manganese oxide mineral deposit of the Urizukuri area was deposited periodically and repeatedly from manganese-rich hydrogenous solution in cavities or fractures generated during the intrusion of quartz-porphyry dyke in Cretaceous age. The manganese component may have been derived from the deep-seated manganese-rich formation.

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