Syntheses of spherulitic rhodochrosites in gels and the natural occurrence.

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.