The xenothermal-type ore deposits of the Toroku Mine are intimately related to granite porphyry which was intruded during the Miocene. The deposits include two individual ore bodies: the contact-pneumatolytic tin-arsenic ore body found near the granite porphyry and the arsenic-and lead-zinc ore bodies occurring in a breccia zone and formed during high-moderate temperature hydrothermial stages. During a late stage of mineralization, pyrite and marcasite deposition from low-temperature hydrothermal solutions has taken place.
The writer has chiefly investigated the following.
1. Sequence of mineralization.
2. Relation between mineralization and distribution of minor elements.
3. Various textures found in ore minerals such as galena, sphalerite, chalcopyrite and arsenopyrite.
4. Alteration in the country rocks formed during the pneumatolytic to hydrothermal stages.

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Cupriferous pyrite deposits of the Okuki and the Nebutoyama Mines are in a very weakly metamorphosed region of Shikoku, Japan, The ore-deposits of bedded or lenticular type are nearly concordant to the country rocks which are mostly volcanic and pyroclastic rocks.
The ores consist of pyrite and chalcopyrite with minor amounts of sphalerite, and galena. Magnetite, hematite and ilmenite are found locally near sulfide ores of the bedded type and also separately in other horizons. A layered texture of "lamina" type is well shown by the ores.
Various kinds of colloform texture of pyrite are commonly found in the ores. On the basis of the mineral assemblage, special well-preserved colloform textures in the ores include (1) angular colloform banding in some quartz-pyrite ores and (2) rounded colloform-pyrite in chalcopyrite-pyrite ores.
Most pyrite. crystals include very small grains of other minerals. This texture is called the "bleb" type. Such "blebs" are found also in euhedral crystals of pyrite. There are many intermediate textures between typical colloform and "bleb" textures. The "bleb" texture of pyrites from the two mines, therefore, seems to have been formed by the recrystallization of original fine-grained pyrite of colloform type.
The presence of such ores in a weakly metamorphosed region suggests formation of the original iron sulfide deposits of the two mines under low temperature conditions and later metamorphosism of the deposits to banded, cupriferous pyritic ores of "Kieslager-type".

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The Kuga Mine is composed of tungsten and copper deposits of two types : (1) Pyrometasomatic skarn type, and (2) quartz-vein type.
Geologically, the district consists mainly of Paleozoic formations that are folded with axes plunging N65°W30°The ore deposits are confined to the crests of folds.
The pyrometasomatic skarn-type deposits were formed by replacement of limestone beds by mineralizing solutions which ascended through tension cracks. The cracks are perpendicular to the fold axes of the Paleozoic formations. The quartz-vein type deposits were formed by filling of the cracks.
The limestone beds were deformed into pipe-like masses which are elongated in the direction of the fold axes by the compressive forces which caused the folding.
Therefore, the location of ore deposits is controlled by the folded structure of the Paleozoic formations, the tension cracks, and the existing shapes of the limestone beds.
The quartz veins include some pegmatitic material. The formation temperatures determined by fluid inclusion methods reflect generally the order of ore deposition, i. e. a general progressive lowering of temperature during the depositional processes.

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The so-called "Don", the igneous rock which intrudes coal seams, from six collieries in the Chikuho coal field has been studied microscopically and chemically. It has been confirmed that all of the specimens of don have common specific characteristics, and it would seem that all belong to a variety of basaltic andesite. However, biotite is always rather abundant in the ground mass and brown hornblende is commonly present. Further, potash feldspar and subordinate quartz are present in considerable amounts. Moreover, the don has always been more or less altered, mainly by the action of magmatic H₂O and CO₂. Two main types of alteration are recognized: sapohitization which occurred at an early stage, and dolomitization of a later stage. The types of alteration and the characteristics mentioned above indicate that the don is also lamprophyric in nature.
Microscopic observations and also comparison of the calculated standard cells make it clear that large amounts of Mg⁺⁺, and Ca⁺⁺, as carbonates, have been transferred hydrothermally into the cinder coal which is in contact with the don.
Don can be classified into several rock types according to mineral associations. A survey of the distribution of each rock type, giving careful consideration to the accompanying geological structures, is useful in prospecting the non-intruded parts of a coal-seamm in the area intruded by the don.

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