The Shakanai mine is located in the so-called "Hokuroku Kuroko ore deposits area" in the northeastern part of Japan. Prospecting of the Shakanai mine had started in April 1962, and seven ore bodies have been found since ore body No. 1 was discovered in February 1963. We planned the prospecing on the basis of some indicators by examining the previous data.
These indicators were partially amended and enlarged according to the accumulation of the geological data, the development of the underground round operations and the extention of the prospecting. The indicators are as follows:
1. The valley-shaped areas on the surface of the so-called footwall rhyolite.
2. The areas where mudostone is developed in the so-called hanging wall formation.
3. The weakly altered zones.
4. The network zones.
5. Explanation of the geological structures.
6. Study of the sedimentation of the country rocks.
7. Consideration of ore genesis.
In the "Hokuroku kuroko ore deposits area", we have recently gained ample data of geology and ore deposits. As a result, we have reached the following conclusion about the genesis of the Shakanai ore deposits.
When the pressure of the ore fluid is balanced with the hydrostatic pressure of the sea bottom, thee ore fluid cannot rise up to the surface of the bottom. If the former was larger than the latter, the ore solution would ascend and ore minerals would be deposited on the sea bottom. It is considered that the pressure might have been balanced and unbalanced alternately so that the ore deposits were formed repeatedly in a comparatively short time in Shakanai and its neighborhood.

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The dolomite deposits in Gifu Prefecture are found, from west to east, in Kasuga-mura and Tani-gumi, Kuze-mura of Ibi-gun, Miyama-cho of Yamagata-gun, and Mugi-mura of Mugi-gun, along with their outskirts. They are situated on an arc whose radius measures 50 to 60 km from Nagoya. City, its center. It should also be noted that pure limestone deposits like those known at Mino-Aaka-saka and Saraji are located inside the arc, almost parallel to the dolomite deposits. Many of these dolomite deposits are found in thick limestone beds as seen in Mt. Ibuki, Mt. Funafuse, Mt. Kita and so on, although some exceptions are found in smaller extensions and also in slate, chert and like, without being accompanied by limestone. The dolomite deposits are generally accompanied by the limestone beds of Parafusulina zones. Therefore, their geological age is Middle Permian.
Staining test disclosed that crystals of the mineral are mostly 0.1 mm in size, a little larger than those found at Kuzuu, Tochigi Prefecture, although not a few are of the same size. Dolomite of Japan is somewhat different from that of foreign countries in that the interstices of crystals are filled up with calcite, and accordingly the dolomite is very compact. Some parts of the dolomite deposits in the Kasuga area, Gifu Prefecture, have undergone thermal metamorphism by the injection of later granite.
Four mines are in operation now, each producing from about 2, 000 to 13, 000 tons per month Grade of the ore is 17 to 19% MgO and 0.5 to 1.5% SiO₂.
Attention should be paid to the fact that the dolomite from the Kasuga area contains the least amount of Fe₂O₃ among Japanese dolomite ores 0.01% on an average. For this reason, it is great demand from glass industry. The mineral is mostly used as refractory material for steel works. Another recent use of the dolomite is agricultural dolomitic lime.

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The three-dimensional structure of a hydrothermally altered mass was revealed by deep drillings for the exploitation of the geothermal resources in Matsukawa. The mass comprises five zones of different mineral. assemblages, i. e. weakly altered zone, montmorillonite zone, kaolin zone, alunite zone and pyrophyllite zone, respectively. The three zones, montmorillonite, kaolin and alunite zones, are zonallyarranged. The followings are discussed:
1. The altered mass as a whole is rather vertically elongated reaching to 720m in depth (from the restored surface at the time of main humarolic activity). The shallower part above the 340m level shows a asymmetrical zoning up to the surface. In the deeper part is recognized a symmetrical zoning from conduit to periphery.
2. The amount of discharge of fluid was probaly larger in the deeper part than in the shallower part. The quantities of migrated elements as a whole were generally larger in the shallower part than in the deeper part, although the tendency of migration is similar.

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