As a result of the geological study of the large area of the volcanic groups of Mt. Iwate and Hachimantai, the stages of volcanic activity related to the sulphur deposits have been determined. It has been possible to draw some important conclusions on the tendencies of the prospecting for sulphur and pyrite deposits in the Matsuo mine.
The author was able to examine a very great number of specimens of ores and rocks, and also chemical analyses of these ores 17, 300 were collected in the east-west drifts extending as long as 100, 000m. From the results of observations based on these data, the position of a diffusion center of ascending mineralizing solutions and vapour was located; the area of its diffusion. center was assumed to be relatively small. The diffusion of mineralizer from the center is the main factor in the formation of the ore shoot in the Matsuo deposit. Therefore, the principle of prospecting in this mine based on the geological and geochemical conclusions was established.

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The Hanaoka mining district is located in the north part of the Odate basin, northern Akita Prefecture. The ore body of this mine is typical of the so-called "Kuroko" which are found mainly in North-eastern Japan. The Doyashiki ore Deposit ekists near the center of Hanaoka mining district and is the largest one we have ever discovered.
The ore of the deposit has been said to have formed, en mass, in rhyolitic tuff, though a few people suggested that it was partly formed in rhyolite. The writer investigated the silicious ore of the Doyashiki ore deposit and as a result found some indications, both structural and petrological, that ore was formed in rhyolite.
In this paper, the writer tries to divide structurally and genetically the Doyashiki and circumambient ore deposits into the five types listed below, and also to delineate the structural control of these deposits, assuming the intrusion of the stock of rhyolite hear the center of the Doyashiki ore deposit.
(1) Ore doposits in rhyolite.
(2) Ore doposits formed in the domed up parts in tuff by intrusion of rhyolite.
(3) Ore deposits in normal fault zone in tuff.
(4) Ore deposits in abnormal folded zone in tuff.
(5) Ore deposits formed in the parts which have combined elements of above described types. The writer believes this study will be useful for future prospectingg and mining.

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It is well known that the chief alteration products in the country rocks of sulphur deposits are opal, sulphur, kaolin, alunite and iron sulphides. According to the writer's study, almost all country rocks of impregnation sulphur deposits in Japan are two-pyroxene andesites and their pyroclastics. The discussion of the alteration processes leads to the following conclusions:
1) By the action of volcanic gases or solutions, the country rocks, whatever their original appearances may be, are ultimately bleached to whitish colours.
2) By percolating solfataric gases or solutions, materials composing the rock-forming minerals of the country rocks, such as alumina, alkalies, alkali earths and iron, are carried away as soluble sulphates and the spaces from which minerals were removed are filled up with various secondary minerals.
3) At first, colloidal silica derived from the original rocks will occupy the spaces.
4) Or this time, sulphur may fill up the space, if the condition is favourable to deposit sulphur.
5) Alunite is the alteration product of feldspars in the country rocks, and it occurs not only in the original feldspars but also around them. In the process of being carried away as soluble sulphate, some feldspars which are partially altered will be changed to alunite by continuously acting solutions or gases.
6) When gases and solutions percolate into the porphyritic rocks, they will attack and alter first the phenocrysts and then the groundmass. This is the reason porphyritic textures remain in the altered country rocks.
7) Secondary minerals in the altered country rocks are deposited repeatedly at the same alteration stage.

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In order to measure precisely the beta-radioactivity of ores in galleries, the present writers have constructed a special beta counter, "Type-DC-P1", which has been confirmed by experiments to be of high quality. It is composed of a lead shielded probe, a tripod, cables, a counter using decatrons, colloid batteries, a charger, a timer and a stand which enables us to perform precise measurement in laboratory using the same probe as in the fields. Its probe and counter are not only water-proof but also air-tight, and can be employed adequately in galleries with air of high humidity or of high radioactivity. Its background count is considerably low and stable. The data obtained by means of the DC-P 1 can be analyzed according to the calculations introduced by one of the present writers (N.K.) in other papers, rendering possible the estimation of content of radioactive isotopes in ores.

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The Iwaki Coal-bearing Beds of the Taira-Yoshima District contain the following six coal seams or groups of seams, named in ascending order : the second Kaso group, the first Kaso group, Honso group, Nakaso, Joso and Funtanso. This coal bearing formation repeats the cycles of sedimentation in a very regular order, beginning with the deposition of sandstone and conglomerate soon after subsidence of the coal area and finishing with the deposition of coal and shale after the silting up of the area. The cycles may be classified into tow types, i.e., the Kaso-type and. the Joso-type.
Coal seams above the Honso group belong to the Joso-type. This type of cycle (or cyclothem) begins with marine sedimentation, represented by sandstone and conglomerate or conglomeratic sandstone accompanying marine shell fossils and sometimes sand pipes, which was caused by a temporary marine invasion after sudden subsidence of the coal-forming field.
Coal seams below the Honso group consist of three groups, each group containing a few coal seams intercalating sandstone and shale, and between each group occurs a dominant conglomerate bed. The coal seams of each group have the tendency to converge into one seam in the western, shallower portion, and, on the contrary, split into several seams in the eastern, deeper region. These belong to the Kaso-type, and the roof of each coal seam is generally composed of shale or inudstone, or, rarely, of sandstone.
The sedimentation bf the Kaso-type must signify that of a lake basin. The transition to the Joso-type above the Honso group may imply the silting up of the basin and the direct connection of the coal-forming field with marine water. The cycles of the Joso-type may represent a sort of deltaic cyclothein, and also possibly a piedmont cyclothem, because of the narrowness of coal field along the coast line. The area of sedimentation in the Joso-type coal seams should have become narrower in each successive seam finally giving way to a purely marine facies without coal.
The roof of the Joso-type of coal seam such as the Honso and the Joso is composed mostly of coarse grained sandstone and conglomerate, and the coal itself has been washed out locally by the action of marine waves and currents, frequently forming a sort of intraformational conglomerate directly above the coal seam. This conglomerate has been named by the writer as "coaly simultaneous conglomerate".
The deterioration of the quality of coal of the Joso-type is caused, on one hand, by the thinning of the coal from above by erosion, or sometimes by the overlapping of the coal directly on the basement rock. On the other hand, the deterioration of quality by an increase in the ash content occurs in the eastern region. Among the Kaso-type of coal seams, the second Kaso group is thick and of good quality where it is deposited in the valley bottoms between hidden hills, which represent the true hills and valleys of coal forming age.
Away from the hidden hill region, however, the coal seam of the second Kaso shows a transition to the mere plant fossil bed with latifoliate tree leaves, and moreover was eroded away, in some places, probably by streams.

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Opal, as well-known, is a amorphous mineral that contains from 3 to 10 per cent combined water, and its molecular formula is given by SiO₂⋅nH₂O.
The writer, to ascertain the effect of opal on sulphur refining, made differential thermal analysis of opaline clay collected from the Matsuo Sulphur mine with an electric furnace that was adjusted to rise 10°C per minute.
The results of the differential thermal analysis indicate that discharge of adsorbed water from the opaline clay is completed at 150°C. And endothermic peak between 400°C and 530°C, is caused by decomposition of marcasite and pyrite which accompany the clay.
If the temperature of the retort is raised higher than 530°C, sulphur is naturally separated from both marcasite and pyrite. But the recovery percentage of sulphur in, the refinery may be less than 100 per cent, because massive ore is used instead of powdered ore as in the laboratory.
On the other hand, it is impossible to dry ore completely that contains more or less opal, by heating higher than 110°C before refining, because it always contains considerable amounts of native sulphur. The ore, therefore, that is sent to the refinery still contains some adsorbed and almost all combined water of opal. This water combines with sulphur to form H₂S and SO₂, if the temperature of the retort rises higher than 400°C.
3S+2H₂O 2H₂S+SO₂
Theoretical and practical volume ratios of H₂S and SO₂ are 100:50 and 100:75, respectively, because oxygen in the air, which flows into the retort during the refining process, combines with sulphur to form SO₂. The amount of sulphur which is collected from the above-mentioned H₂S and SO₂ in the reaction tower is restricted by the volume percentage of H₂S:SO₂=100:50.
So, nowadays, in the case of the Matsuo mine, excess S0₂ gas is wasted.

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Fluorine is generally considered important in the formation of pyrophyllite deposits, but the available, published analytical data are still insufficient to confirm this.
The authors give the fluorine content of various rock samples from the pyrophyllite deposit of the Yonago mine, Nagano Prefecaure. They also give the distribution of some heavy metals in these samples.

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Recently, ilmenite deposits associated with gabbro-amphibolite have been found in the central Hokkaido.
Gabbro-amphibolite regarded to be derived from olivine-gabbro is classified into several facies; epidote-chlorite-amphibolite, epidote-amphibolite, amphibolite, saussuritegabbro, etc..
Ilmenites are concentrated in the pegmatitic gabbro-dykes found in a part of the saussuritegabbro. Some of them were recrystallized, and regenerated deposits were formed. Extend and grade of the deposits are not yet clarified.

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