The characteristic properties of gold-silver ores from the Todoroki ore deposits and the Nakanosawa ore deposits which are epithermal gold-silver quartz veins of Tertiary age in the southwestern part of Hokkaido, were studied, and some conditions of ore formation are discussed.
The Chuetsu-hi vein and the Shuetsu-hi vein, principal veins in the Todoroki ore deposits, are similar in the vein scale, the vein pattern, the trend of ore shoots, the mode of occurrence of ores, the ore textures, the mineral assemblages of ores, and the wall rock alterations. And the Nakanosawa ore deposits show similar characteristics as regard the vein pattern, the trend of ore shoots, the mode of occurrence of ores, and the wall rock alterations. The wall rocks, however, differ among veins (i. e., Chuetsu vein; rhyolite and its pvroclastic rocks. Shuetsu vein: sedimentary and nvrcclastic rockc Nakanosawa ore deposits; dolerite) and gold-silver ores show different features in mineralogical and chemical compositions, and in the properties of some constituent minerals.
Data on the fluid inclusion, mineral associations and chemical compositions of minerals give some similar but slightly different physicochemical conditions of ore formation between the Chuetsu-hi vein and the Shuetsu-hi vein.

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In order to study the failure criterion of rocks under the combined stresses, the biaxial tests were undertaken on three kinds of rocks, namely OGINO tuff, KAWARAGO tuff and KIMACHI sandstone. For these tests, a biaxial testing machine using the rock plate specimen was designed as shown in Fig. 3 and Fig. 4.
The main results obtained in this study are summarized as follows;
1) The failure strength of rocks under the combined stresses of compression-compression changes with the intermediate principal stress as shown in Fig. 6. The maximum value of failure strength of KAWARAGO tuff in compressioncompression test is about 1.4 times the uniaxial compressive strength, KIMACHI sandstone about 1.9 times and OGINO tuff about 1.3 times. The increase of failure strength of rocks incompression-compression test shows that the magnitude of the intermediate principal stress has a considerable influence on the magnitude of the fracture strength.
2) The failure limiting line of rocks in compression-tension test gives the curved line part and the straight line part. The curved line part shows the range which the failure strength of rocks decreases as the tensile stress increases, and the straight line part shows the range which the failure strength approaches gradually to the uniaxial tensile strength.

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Four-point bending tests were undertaken in a triaxial vessel for fine grained and coarse grained AKIYOSHI marbles to reveal the features of bending fracture under confining pressure.
Main results obtained in this study are as follows:(1) When the confining pressure is sufficiently high, the fracture cracks are arrested and, accordingly, the fracture propagation becomes more stable than that under low confining pressure where the rupture takes place immediately after fracture initiation.
(2) The bending moment-outer fiber strain diagram of fine grained marble shows sudden drop of bending moment caused by fracture initiation (Fig. 4 (a)). On the other hand, bending moment in coarse grained marble increases monotonously until rupture (Fig. 4 (b)).
(3) The outer fiber bending stress at fracture initiation increases rapidly with the confining pressure for both fine grained and coarse grained marbles. This suggests that the conventional failure criterion can not predict the outer fiber bending stress at fracture initiation under confining pressure (Fig. 11 (a) and (b)).
(4) Number of fracture cracks initiated between the two loading points increases as the confining pressure increases and decreases as the thickness of the specimen increases (Table 2). On the contrary, average ratio of the length of arrested fracture crack to the thickness of the specimen decreases as the confining pressure increases and also decreases as the thickness of the specimen increases (Table 3).

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The features of the roof subsidence in the level entries, caused by mining a horizontal coal seam, are studied by analyzing the results obtained by survey in the coal burst. area of Miike mine. It is concretely found out that the progress of the roof subsidence in the level entries not only concerns with the distance from the longwall face and the change of geometrical shape of the mined area, but also concerns with the discontinuities in the roof, as shown in Fig. 5 and 6. Correlating withth e length of the level entry, where the roof subsidence is growing up with the face advance, the frequency of coal bursti ncreases as shown in Fig. 9 and this length is related to the intervals of the discontinuities as shown in Fig. 7. In the case that the rigid hangingwall is directly lying on the coal seam, we conclude, this length reflects the magnitude of the pressure acts on the abutment.

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Referring to the agglomeration of particulate materials with the aid of hot melt binder like thermoplastic resins we gave a deductive discussion through some numerical evaluations according to a binder bridge model which is introduced through the modification of an wellknown model about liquid bridge between two neighbouring homegeneous spheres. Our discussion is restricted within the case where particulate material is composed of homogeneous spheres and that the porosity of the agglomerate is located in a limited range.
The results may be summerized as follows: a. A critical mixing ratio of binder to spherical particles required to get an agglomerate with satisfying strength was proposed, which depends not on the size of particle, but on the contact angle of the binder to particles and the porosity of the agglomerate to be prepared.
b. It is recommendable to choose binders with lower contact angle to particle for the purpose of saving the consumption of binder.
c. The dimensional ratio of liquid bridge to spherical particle does not depend on the particle size if the mixing ratio of binder and the porosity of agglomerate are fixed.
d. As the adhesive strength of hot melt binder to solid particle is normally much smaller than the tensile strength of binder material, it is to consider that the-binding mechanism between particles depends on whether particle surface is fully coated with the binder through the preliminary mixing of particle-binder system.
In either case, we think, the procedure mentioned in this paper indicates a possibility of estimating tensile strength of form agglomerate.

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Laboratory tests of vat leaching of easy-to-solve uranium ore were made to obtaina general understanding of the characteristics of leaching and washing of uranium ore. The neutralization of waste water and of leached residues were also studied. The ore utilized in this work was low grade and coarse uranium ore from Yotsugi deposit of Ningyo-Toge mine.
It was found that a high recovery of uranium, say 88% plus, is readily achieved by leaching coarse and low grade ore (-150mm and 0.07%U) in a vat with sulphuric acid solutions. The period required for leaching and washing was around two weeks in total. Flow rates of leach solution were determined as a function of the height of ore bed in the vat. Flow rate of leach solution was sensitively affected by the height of ore bed.
The usage of caustic soda for the surface treatment of leached residue was found to be more preferable than that of lime, resulting the efficient depression of the dissolution of uranium.

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Thermodynamic calculations were applied for the new idea of zinc smelting, in which hot calcine, coke breeze (or powdered coal) and air (or enriched air with oxygen) were injected in molten slag and lead bullion.
The compositions of slag, lead bullion and gaseous phases were calculated and the heat balance in the reaction furnace was obtained under various conditions by using GOTO model. The effects of the reaction temperature, amounts and the compositions of calcine, coke breeze and air, and the degree of the enrichment of oxygen in the air on the compositions of slag, lead bullion and gas, and the heat balance in the furnace were calculated.
It becomes obvious from the calculation that the amounts and the ratios of calcine, coke breeze and oxygen injected in slag per unit time are the important factors for maintaining the constant zinc content in slag without iron precipitation and keeping the constant temperature in the furnace.
In points of energy conservation and energy cost, the optimum conditions were obtained by using hot calcine and nearly pure oxygen.

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Reduction rate of PbS with H₂ was measured thermogravimetrically in the temperature range 380°to 750°C by using thin disks prepared from synthetic and natural PbS powder.
The reduction rate of synthetic PbS was about twice that of galena below 450°C, whereas above 650°C no difference was detected in their rates. The rate decreased when a sample was covered with the formed metallic Pb at 550°C, but the tendency was not observed at 710°C. The measured rates surpassed the vaporization rates of PbS significantly and the Arrhenius plot yielded two straight lines. The activation energies were determined to be 15 kcal/mol below 450°C and 33 kcal/mol above 650°C respectively.
It can be presumed from these results that the reduction in the lower temperature range is governed by a mechanism different from that in the higher temperature. At temperatures below 450°C, the experimental results suggest that the rate is chemically-controlled by the heterogeneous reaction between H₂ and solid PbS. Absolute reaction rate theory was used to develop an analytical expression for this heterogeneous reaction. The rate constants calculated with the equation assuming that the surface of PbS is sparsely covered by adsorbed hydrogen agreed favorably with the experimental data.
On the other hand, above 650°C, it can be suggested that homogeneous reaction between gaseous PbS and H₂ is dominant and the reaction proceeds not at the surface or in the bulk stream of H₂, but in the boundary gas layer and enhances vaporization of PbS. The model can be supported by the following observations:(1) The surface of the reduced PbS at high temperature shows a similar structure to the surface which is allowed to evaporate under reduced pressure.(2) Reduction rate is independent on the size of the grains which comprise of a sample disk and also on the much adhesion of metallic Pb on the surface.(3) Serious difference in the activation energies in the reduction and vaporization.

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