Matsuo Nambu

Hydrous ferric oxides in the “Takashi-Kozo” from Bessho, Shiga Prefecture

Hydrous ferric oxides in the so-called “Takashi Kozo” (limonitic nodule in Quaternary sediments) from Bessho, Shiga Prefecture are identified as the amorphous type by means of microscopic and X-ray examinations and of differential thermal and chemical analyses.

Thermal studies on the replacement textures of ore minerals

Pure chalcopyrite (about 6mm in diameter) and metallic bismuth sealed in the same glass tube are heated at temperatures from 271°C to 700°C for 1 ?? 5 hours. Then they are quenched in ice water or slowly cooled in the electric furnace and examined carefully under the reflecting microscope. The results obtained are as follows: (1) Chalcopyrite dissolved into Cu2s, Cu5FeS4(or Cu2S solid solution), FeS, CuFe2S2 and metallic copper. Between them following four types of crystallographic intergrowth can be observed: (a) Lamellar bornite in chalcopyrite, (b) Lamellar ?? banded cubanite in chalcopyrite, (c) Lamellar ?? lattice chalcopyrite in bornite, (d) Lamellar chalcocite in bornite. (2) Predominant textures resulted from the replacement of chalcopyrite by molten bismuth are as follows: (a) Emulsion-sea and island type, (b), Veinlet ?? network type, (c) Graphic ?? pseudoeutectic type. Emulsions are often observed in the crystallographic direction of chalcopyrite, but iamellar or lattice replacement textures appear to beless common. (3) The formation of bismuthinite may be expressed as follows: 2CuFeS2=Cu2S+2FeS+S 2Bi+3S=Bi2s3. Bismuthinite can be classified into the following three types according to the positions of crystallization. (a) Reaction rim along the boundaries between chalcopyrite and bismuth, (b) Idiornorphio crystal in bismuth, (c) Island-like or emulsion in chalcopyrite.

On the Formation of Copper Ores from the Ômine Mine

It is possible to determine the paragenesis of the nine ore minerals and eleven skarn or gangue minerals in the deposit of Omine mine by microscopic examination. On the other band, there are at least eleven kinds of unmixing intergrowth found in the metallic minerals, as has been reported previously. The unmixing temperature of them is known only in a few cases of them. Hereunder, the ouder of the 11 unmixing intergrowths, is assumed by introducing some hypotheses on unmixing, and combining the results with the paragenesis of the ore minerals determined by microscopic examination, in order to unravel the process of growth of the ores. However, there are as yet some details which require further research.