1) Electric logging, used commonly in oil fields, requires some modification of instruments and methods for the purpose of exploration of boreholes in coal fields, where permissible error in determining thickness of seams is on the order of a centimeter. Therefore, standard. (45 mm in diameter, electrode interval : 100-250 mm)and micrologging(120 mm in maximum expansion, electrode interval : 25 mm) electrodes were designed, and were carefully removed from boreholes at a slow speed. (minimum, 100 meters per hour).
2) Since 1953, more than 20 holes of 50-1400 meters depth in the Ishikari (Hokkaido) and Saga (Kyushu) coal fields were tsted by the Mitsubishi Mining Company with improved instruments and measuring methods, and results have proved that electric logging is effective even in the case of coal exploration.
3) Main results :
a) Coal and partings more than two centimeters thick could be detected.
b) Columnar sections of holes where coal was not recovered could be adiusted.
c) Drillers could be checked when no coal was recovered.

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The lenticular manganese ore deposit of the Nodatamagawa mine in the northern part of Iwate Prefecture is concordant in Paleozoic quartzite and was formed after the high grade thermal metamorphism by granitic rock intruded as a batholith near the mine. The ore bodies, constituting the ore deposit of this mine, lie concordantly on near a single horizon of quartzite. This horizon is called "the horizon of ore deposition" for convenience.
The Misago Ore Body is largest and has a very complex form controlled by folding of the country rock; the bonanza is elongated along the fold axis to more than 420 meters from the outcrop. The inner part of the ore body generally consists of manganese oxides, namely pyrochroite and hausmannite with small amounts of manganosite, alabandite, rhodochrosite, braunite, etc., the outer part consists of the manganese silicates, rhodonite and tephroite.
The authors were able to distinguish easily the quartzite of the hanging wall from that of the foot wall on the basis of their appearance and microsocpic features, especially the texture, and the accessory minerals, biotite, garnet, etc.. Therefore in this mine, a prospecting method based on microscopic study and a survey of folding in the country rock was very useful and successful.

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Two genetic types (i. e. primary and secondary) of iron-sulphide exist at the Horai Tokamatsu mine, Akita Prefecture.
The primary iron-sulphide ore was deposited by ferruginous spring action and mineralizing gases or solutions, before limonite deposits were formed. The secondary iron-sulphide ore is the replacement product of limonite by mineralizing gases or solutions.
The results of spectroscopic analyses of the two kinds of ore are shown on Table No. 2. From these it is evident that zinc occurs in both primary and secondary iron-sulphide but not in the limonite ore. It seems to the writer that the zinc has been added by solfataric gases.
The fact that natorium exists in the ferruginous spring, the limonite and its replacement ironsulphide ore, but not in the primary iron-sulphide ore, suggests an important control in the genesis of the deposits.
The X-ray powder pattern of the primary iron-sulphide is very simillar to that of pyrite as seen on Fig. 7 and Table 5, whereas the secondary ore is a mixture of pyrite and marcasite as shown on Fig. 7. Both iron-sulphides seem to have been crystallized under conditions of weak sulphuric acidity and relatvely low temperatures, as suggested by Allen's and Grenshaw's laboratory experiments. This conclusion is also supported by hydrogen-ion concentration of the ferruginous spring.

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The Ôgane mine, situated to the east of the Suttsu Bay, is one of several mines located in the mineralized district of Cenozoic era in southwestern Hokkaido. In this area, green tuff and tuff breccia are intercalated in the middle part of a Miocene igneous series consisting of quartz porphyry, hornbende andesite, propylite and two-pyroxene andesite. Ore mineralization took place in the igneous rocks and tuff breccia along an anticlinal fold-axis.
The ore deposits of the Ôgane mine are epithermal gold-silver veins. On the basis of minerals forming them the veins are classified as follows: quartz-rhodochrosite veins, quartz-sulphide veins, telescoped chalcopyrite-sphalerite-galena veins and barite-quartz veins. These veins are in masses of propylite, two-pyroxene andesite and green tuff breccia, and are located in the inner part of a dome, structure on the anticlinal fold-axis.
The Nishitani-vein group, which is one of four groups in the Ôgane mine, consists of three parallel veins deposited in propylite. The propylite surrounding the Nishitani vein group has a zonal structure that includes a chlorite-carbonate zone, an albite-sericite zone and a sericite (?)-quartz zone. This structure probably was formed during the late stages of propylitization.
The some width of wall rock was, in general, altered strongly: the altered rocks are subdivided into the following three rock facies: a carbonate-chlorite rock, a quartz-sericite rock and a sericite(?)-quartz rock. These altered facies must have been important channelways for the solution, The ore minerals of the veins are pyrite, chalcopyrite, sphalerite, galena, tetrahedrite, native gold, electrum and silver minerals; gangue minerals are quartz, adularia, rhodochrosite and barite,
It is inferred that ore mineralization had three phases as the veins can be divided into a sulphide zone, a rhodochrosite zone and a barite zone. The sulphide zone includes great numbers of gold particles; the rhodochrosite zone generally has lower gold values. The particles of native gold are present as round grain sand are closely associated with chalcopyrite and sphalerite.
After the ore mineralization the Nishitani-vein group was disrupted by strike and oblique faults. The faulting which took place was closely related to location and control of the ore deposition.

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The Pre-Tertiary basement underlying the main coal bearing strata, Hanakawa Formation, developed in the Joban coal-fields, often produced buried hills in the overlying beds. The develop-ment of the workable coal seams has been influenced by the existence of the buried hills; namely, the main coal seams all tend to become thinner as they approach the hills and thin out abruptly or gradually at the tops of them. Accordingly, predicting the location of the hills is important to the coal mine engineers.
The author, co-operating with the field technicians, has recently discovered a technical wise saying "a discovery of grey-greenish schistose mudstone and angular schist fragments in the boring core give us a definite hint on the existence of the buried hills around the boring stations".
This is due to the development of the dark-grey-greenish schistose mudstone zone which proba-bly resulted from the direct transportation of eroded materials derived from the buried hills. If we recognize this characteristic facies in the boring core, irrespective of the distance to the Pre-Tertiary basemant, we can determine concretely the same zone and consequently discover the presence of a buried hill.

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In my last report on the radioactivity of coal and attendant rocks in the Saga Coalfield(Vol. 6(4)of this magazine), the relatively high radioactivity of all things in the vicinity of a rhyolite intrusion in the mine of the Meiji Saga Coal Mine was noted. But, as the measurements were performed in an existing gallery, it is suspected that the results maybe due to the direct influence of the rhyolite, though there may be practically no influence of the accumulating β-ray sources on account of the full ventilation of the mine. The writer, then, directed to take and send the hand-samples of the coal. and rocks at the points where the counts were taken to ascertain whether or not these things by themselves have relatively high radioactivity compared with those of other places. The measurements were done in Tokyo, and the results showed that radioactivity of these samples, measured 12 days after they were taken, also increased according to the nearness to the rhyolite intrusion(Tab.1), as those of matters in the original places, while the samples from other parts of the mine where the igneous rock is absent showed the normal low counts(Tab.2). It is, therefore, concluded that the radioactive influence of the rhyolite intrusion, permeates the coal and walirocks in its vicinity, and that the influence is greater near the intrusion, though it is not yet certain whether the it is limited to the mine wall or is more wide-spread.
The intrusion of basic volcanic rock such as basalt, on the other hand, seems to have no such influence on the coal-measures, according to the recent survey in the Akaike Coal Mine Fukuoka Pref.(the data are omitted). This is to be expected from the low counts of basalt itself both in the original rock-body and in hand-samples(Tab.3). Moreover, it is to be noted that the radioactivity of basalt differs according to its surroundings. As shown in Tab. 3, radioactivity is extremely low where basalt is intruded in the coal seams, while it is relatively high where it is in contact with shale. Basalt in this area seems to be very low in its radioactivity, but may be somewhat higher than coal.

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