The modern industrial society, has progressed from the agricultual society in this Century, is going to change to the more systematic society by means of many technical inovation in the 21st Century.
Under these circumstances, the writer would like to discuss the future of the Japanese Mining Industry in this paper. The main items are as follows.
1) The past results and future forecasts of mining industry.
2) The future of the fossil fuels.
a) The relations between fossil fuels and other energies.
b) The expectation for the new utilizations of fuel cell and MHD generation.
c) The utilization of fossil fuel as the resource of hydrocarbon.
d) The development of carbonic industry in future.
3) The use of metals and non-metals as materials in future.
4) Searching for natural rosources.
a) Effective use of domestic resources and the developments of overseas resources.
b) The Ocean exploitation.
5) The means of promoting future enterprises.
a) The rationalizations of enterprises.
b) The integrated industry and value augmentations.
c) The development of large-scale projects and the merging of enterprises.
6) Some plans for technical innovations.
a) The new methods of prospecting and boring.
b) The underground gasification of coal.
c) The underground liquefaction of coal.
d) The leaching techniques.
e) The approachs for the development of offshore oil fields.

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Usually the separation of various minerals depends upons flotation that is related to the surface property of mineral particles.
On the other hand, the new separation method, that utilizes the defference between elastic stress and breaking resistance while each particle is impacted, will have the possibility to become the technique of great interest in the field of mineral dressing in the next 21st century.
This method is based on the kinetic energy in ultra high velocity flolow of fluid. Therefore both the size reduction and separation are done simultaneously and sharply.
This paper is concerned with the new method with complex sulfide ores from the theoretical and practical points of view.

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Mankind has, in advancing the culture by the discovery and utilization of mineral resources, enriched his living. In order to carry on and maintain the culture, increasing quantity of mineral resources are yet to be consumed. But, there is no guaranty in the long run, if we rely on only the ore deposits that has occurred through natural actions. To maintain the eternal human culture, we must study the new technique to secure the mineral resources.
For this purpose;
(1) The creation of artificialo re deposit by underground neuclear explosion.
(2) The development and utilizationo f subterranean heat and.
(3) The developrhent of Magma for the creation ofartificial ore deposits are problems that urgently need studying and the approach to these problems will be the subject of future mining technique.

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In connection with the study on deep underwater blasting for shaft sinking by well sinking method, the characteristics of the stress waves induced in a hard clay seam and in a concrete material by an explosion of explosives were studied experimentally and discussed in this paper.
The experiments for the study of the stress wave in clayey material were carried out in a hard clay seam located in Hirokawa district in Fukuoka prefecture and those for the study of the stress wave in concrete material were carried out in a large block of concrete.
One of the most important results obtained in this investigation is as follows.
Let's consider the polar coordinate of which origin is the centre of the charge of explosives. Then, at any point in both the hard clay seam and the large block of concrete, the maximum values of the dynamic radial stress, γγ max, and the tangential stresses, θθmax and ΦΦmax, which are induced in these materials by the explosion of explosives, decay with distance from the charge and the relations between these values and the distance, r, and the quantity of explosive, W, can be represented by the following expressions, γ_max=K (γ/W 1/3) ^-n, θθ_max=ΦΦmax=K'(γ/W1/3) ^-n', where n and n' are the decay exponents peculiar to the material andKandK'are constants.

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There are many troubles to mine “Kuroko” are body, due to the soft and plastic properties of the country rock.
“Underhand horizontal slicing with back filling accompanied with artificial roof made of reinforced cement mortar” has been successfully adapted to mine the are and to support the heavy and troublous rock pressure.
It is fact that the rock pressure observed under the artificial roof is very much lowe r than the rock pressure presumed on the elastic theory.
In this report, a consideration on the mechanism of reducing rock pressure under the artificial roof is discussed.

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In such a case that Bingham's fluid flows in laminer flow for circular tube, the equation of pressure drop (P/L) is obtained as follows:
P/L=32μ_BV_D/Dφ=4τ_y/Da where Φ=1-4a/3+a⁴/3
Planning the hydraulic transportation of slurry, the equation must be applied in case that slurry is Bingham's fluid, and the value of plug radius (a) must be determined for calculating pressure drop.
Although the trial method was proposed by E. L. McMillen for determination of plug radius, the method requires much trouble.
Then, a handy method named differential method was induced by the authors. In this method, the value of plug radius is determined by the differential coefffcient (tanθ) of curve which is obtained from the relation between the pressure drop (P/L) and the mean velocity (Vm) of Bingham's fluid plotted on the logarithmic graph.
The relation between of plug radius and the differential coefficient is obtained as follows:
tanθ=1/(1+4a (1-a³)/(3-4a+a⁴))
As the value of plug radius is calculated by the above equation or the (a-θ) diagram, the new method is very convenient in comparison with the trial method. The above relation was certified by the experiment using the slime slime slurry of Ashio mine.

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For the effective concentration of low grade iron ore, the author developed a new top feed type magnetic roughing concentrator. The specifications of the structure of this concentrator is shoun in Fig.6. It consists mainly of two mechanical parts, the one is a shaking feeder equipped with magnets for the acceleration of consolidation trickling of magnetic particles, and the other is a drum type magnetic separator deeply immersed in water. Due to the shaking motion of the feeder, magnetic particles are previously stratified by their specific gravities and magnetic properties, thus magnetic particles are reasonably attracted to the magnetic drum. The fundamental characteristics of this concentrator were experimentally investigated by using iron sand. Fig. 8, 9 are the results concerning the Misawa iron sand (magnetite content m=1.9%) and Fig.10, 11 are the Iioka iron sand (magnetite content m=19.0%).
Fig.8, 10 are the relations between the peripheral speed v of the separation drum and the grade of talilngt, where the paremeter is feed rate F.
In the lower range of less peripheral speed than v=65m/min, the grades of tailing decrease to the order 0.00%.Consequently in the same lower range of the peripheral speed recoveries E increase to about 100%, which is shown in Fig. 9 and 11. From these fundamental investigations we confirmed that by the applications of the top feed method to the magnetic concentration low grade iron ore which could not be separated by the ordinary magnetic separator can be effectively concentrated.

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Each molten slag of FeO-Fe₂0₃-Si0₂-ZnO, FeO-Fe₂0₃-Si0₂-CaO-ZnO, FeO-Fe₂0₃-Si0₂-Na₂O-ZnO, FeO-Fe₂0₃-Si0₂-Al₂O₃-ZnO, and FeO-Fe₂0₃-Si0₂-Al₂O₃-CaO-ZnO systems was brought into equilibrium with a gas mixture of CO, CO₂, and Zn vapor which was prepared through reduction of pure ZnO pellets with a CO-CO₂ gas mixture. The temperatures of the slag and the ZnO pellets were about 1, 100°and 1, 200°C, respectively, and the activities of ZnO in the molten slags, calculated from these temperatures, were about 0.3.
An increase in the basicity of each slag results in an increase of the activity coefficient of ZnO, γzno.
Replacement of FeO by Na₂O and CaO increases γzno, and the former is more effective than the latter. When FeO is replaced by Al₂O₃, γzno decreases, slightly which shows that Al₂O₃ is a little less basic than FeO.
When the slag compositions lie in the range of the current work, a decrease of 0.1 in the mole fraction of SiO₂ results in an increase of about 0.53 in γzno in the case of FeO-Fe₂O₃-SiO₂-ZnO system, and Al₂O₃ does not behave as an acid oxide in both cases of FeO-Fe₂O₃-SiO₂-Al₂O₃-ZnO and FeO-Fe₂O₃-SiO₂-Al₂O₃-CaO-ZnO systems.

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In the first paper, it was described that the prebaked anode. of intimate mixture of magnesium oxide and carbonaceous materials was successfully applied in a small scale reduction cell contatining electrolyte consisted of magnesium chloride and sodium chloride. In this study, the electrolysis was continuously carried out for 64 days by using self-baked anode (Söderberg anode) instead of the prebaked one in the 1, 000-2, 000 amp cell.
The results are summarized as follows.
1) During the electrolysis, the anode was gradually baked from the lower part to the upper one by heat transfer from the bath and heat generation owing to its own electrical resistance.
2) The lower part of the anode was sometimes seperated from the upper part and fell into the bath because the baking was not always enough.
3) Magnesium chloride was formed by reaction of anode materials with chlorine generated on the anode surface, but a small amount of chlorine was sometimes detected together with carbon monoxide and dioxide in the anode gas since the reaction was not perfect.
4) The cathodic current efficiency was 71% on the average. It was observed that some magnesium metal particles were partially covered with black floating matter which happened to appear in the bath and coagulation of the particles was disturbed.
5) A slimy matter called “sludge” was apt to accumulate on the bottom of the cell and the bath had to be. kept clean by removing the sludge at intervals.
6) It is preferable to perform the electrolysis by using such a self-baked anode in a much larger scale reduction cell.

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The committee of the underground gasification had been organized in the Ministry of International Trade and Industry in 1965-67, and planned the underground gasification trial at Naie in Hokkaido.The members of the committee continually planned the underground gasification trial at Takamatsu in Kyushu.
These plans cannot be carried out at present, but we published this paper for future reference.
I think that we must keep up the underground gasification of coal.

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