The ore deposit of the Chichibu mine belongs to pyrometasomatic type.
The formation of the Daikoku fault in the Daikoku ore bodies and of the Akaiwa-toge fault in the Doshinkubo ore bodies was related to the intrusion of quartz diorite. The former is a normal fault caused by magmatic upheaval, and the latter is a hinge fault along the zone where the orientation of the front of magmatic upheavalchanges abruptly. They were important paths of the ore-foming fluid.
Fractures or joints at the eastern periphery of diorite intrusive in the area of Wanaba ore bodies, striking N-S with the dip of 90°were also formed by magmatic upheaval.
Two sets of fractures or joints (N25°W, 80°SW and N55°W, 20°NE) in the inner part of the same intrusive (main adit at 900mL) were formed by the solidification of magma.

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The authors now study thermal fracturing of rocks by supersonic rocket flame jet. Making a good and efficient rocket burner and increasing of thermal fracturing efficiency of rocks require study of physical property variations of rocks with elavated temperature.
In this paper the authors report some measuring data of the linear coefficient of thermal expansion and Young's modulus in high temperature. Our paper shows these physical properties in high temperature different from the room temperature data. As specimens of rocks, we used granite, sandstone, andesite, rhyolite, pottery stone, limestone, and tuff.
These data are available for evaluation of thermal stresses in rocks in thermal fracturing.

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The methods of the development of coal mine has been changed by the progress of belt conveying in Japan. Recently, it has begun to be recognized that the belt conveying system by incline shaft is more reasonable than cage or skip winding system by vertical shaft.
This holds good for metal mine, and long belt conveyor of 4, 500m transport length has already been used at Bessi copper mine. It is increasing to apply this system at several metal mines.
In this paper, author describe a few comments on the economics of the belt conveying system on the basis of the data in the coal mines.

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A theory of an outbreak of spontaneous combustion has already been published following a quantitative study of causal factors of spontaneous combustion. The study is concerned with the rise in temperature accompanied by oxygen absorption from the air.
In this paper the results of new developments of the theory are reported. Here an application of the theory as calculation of crossing-point of coal was made.
We determined the crossing-points for some Minami-Oyubari coals and found that for slower rates of heating of our oil bath, the crossing-point was both theoretically and experimentally lowered significantly.
Thus, the crossing-point of coal does not relates to the accumulation of heat but to the oxidation rate and rate of heating.
Therefore the comparison of the crossing-point among some kinds of coal used in the experiment may show the susceptibility of their spontaneous combustion, but it cannot be very important in suggesting the practical preventive methods.

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Some investigations were carried out on the characteristics of a control system applied to a closed grinding circuit consisting of a wet ball mill and a hydrocyclone. Principally the phase margin was introduced as a criterion in evaluating control quality of the system. In this case it was determined on the Bode diagram of the open loop transfer function of the system optimized by Ziegler-Nichols' method.
Conclusions thus obtained can be summarized as follows.
1) It was found that misplaced fine particles in the cyclone underflow reduced the quality of the control system.
2) The two different controlled variables-the circulating load and the cyclone feed-were compared from the viewpoint of control. Under the conditions considered here the former variable seemed to be preferable.
3) Even in the case, however, when the latter should be adopted as the controlled variable, the system can be improved by applying the so-called ‘cascade controlling method’.

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Fundamental studies have been made on the hydrometallurgical treatments of complex sulfide ores, especially on the selective leaching of zinc minerals.For this purpose the solution potential of the sulfide mineral suspension was measured by platinum electrode and saturated calomel electrode, both being immersed in the solution.The potential values measured for cuprous and cupric sulfides and pyrite corresponded approximately to the mineral-electrode potentials (theoretical values) given in the literature. The relation between the potential and the dissolution pct.at 97°C and with 1M sulfuric acid solution was investigated for simple sulfide minerals such as pyrite, chalcopyrite, covelline, bornite, and chalcocite.The results showed that the potential values for copper dissolution were about 400 mV for chalcopyrite, about 330mV for CuS, and about 240mV for Cu₂S in the primary stage.
Consequently, for preventing of the dissolution copper it is necessary to treat complex sulfide ores under the respective potential mentioned above.The similar experiments with sphalerite and galena were also carried out.But, as these minerals dissolve with the evolutions of H₂S, the mode of dissolution of the minerals is quite different from that of the copper-iron sulfide minerals mentioned above.

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In the electrolytic extraction of metallic magnesium, graphite anode and iron cathode are generally used to supply a direct electric current through an electrolytic cell filled with fused magnesium chloride and alkali chloride (sodium chloride or potassium chloride). Then free chlorine is generated on the anode and reduced metal on the cathode.
In our experiment the baked anode of intimate mixture of magnesium oxide and carbonaceous materials was used instead of the graphite anode and the following results were obtained.
1) A very small quantity of free chlorine is detected in the gas formed on the anode and its main constituents are carbon dioxide and carbon mon-oxide.
2) The change of magnesium chloride content in the electrolytic bath is very small.
3) The anode is gradually consumed during the electrolysis and its surface in contact with fused salt becomes porous.
These results show that the free chlorine reacts with magnesium oxide and carbon-as soon as it is generated after the discharge of chloride ion on the anode surface and magnesium chloride formed by this reaction is dissolved in the bath. Therefore it is possible that the electrolysis is continuously carried out by using such an anode without additional supplying of magnesium chloride to the bath.

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