In the Hanaoka Mine there are more than ten ore bodies, all belonging to the so-called Kuroko deposit (black ore deposit). Results of the writer's studies on this deposit are as follows:
1) As a whole, the ore deposit shows all the characteristics of the Kuroko deposit, but reviewing the individual ore bodies, many of them do not have the characteristics of the Kuroko deposit. The part known to be the Kuroko ore (black complex ore) is not abundant, and is estimated to comprise no more than 1/30 of the volume of the ore bodies as a whole.
2) All of the ore bodies are found at very shallow depth, and oxidation of the ore bodies is not marked, although the action of secondary enrichment is seen even in the deepest part of the known ore bodies. The effect of secondary enrichment is less distinctive on the black ore in the upper part of the ore bodies than on the yellow ore in the lower part of the same ore body.
3) Along the boundary between the ore body and the wall rock different features are seen, depending upon the variation of the characteristics of ores and wall rocks.
4) Silicification took place in all stages of the deposition of various kinds of ores. However, some effects of silicification can probably be attributed to the action which took place after the eruption of liparite.
5) Chloritization of country rocks directly connected with ore deposition is not intense, while extensive chloritization of the liparitic tuff is widely observed in this district.
6) Argillization of the wall rock, and the formation of clay minerals in the ore bodies is very noticeable. The clay minerals vary with their mode of occurrence.
7) The sequence of mineralization is as follows : 1. siliceous ore; 2. yellow ore; 3. black ore. The succession of minerals may be established from the principal ore minerals which compose these ores. The black ore is very complex in mineral association, having-many varieties, and so the succession of ore is considerable in the black ore itself.
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