According to the experience in mines, the phenomena that occur in underground openings related to the loss of the openings stability, are of the following five types.
Partial-breakdown in openings caused from defects of rock itself, the phenomena that occur in longwall mining stopes in coal mines and cut and fill mining stopes in “Kuroko” mines, where the openings are filled up with falling hangingwall rock, or swelling peripheral rock to balance stresses around the openings, chimney caving, rockburst collapse of the horizontal pillars in open stopes of the large-scale massive ore bodies.
Particulary breakdown from defects of rock and the chimney caving among the above mentioned cases are significant for the stability of openings that are planned for underground utilization.
In the case of breakdown from the defects of rock, large scale breakdowns mainly belong to those which are caused by the weak plane that intersect with the walls of openings at low angles. The width of openings affects its possibility significantly. “Width of openings”, “characteristics of rock” and “depth of opening” are the major factors in the chimney caving. The characteristics of rock considerably vary, depending on their humidity. The stability analyses of openings having been carried out up to the present do not agree with our experience, for they are considerably influenced by shapes of openings and very little by their size. This is so because the analyses are based on the essential earth pressures, while we have mainly experienced breakdowns from defects of rock and chimney cavings that are not phenomena caused mainly by the essential earth pressures.

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In an attempt to clarify the effectiveness of machine drivage on roadway deformation, field measurements of vertical closure were carried out both in the roadway driven with a roadheader and with drill and blast. A theoretical discussion considering the interaction between support and rock mass was also made.
The results show that there is no significant difference in the deformational behaviour of roadway driven by each method. This is related to the deterioration of the surrounding strata by the presence of water and the setting conditions of the support. A suitable support system to the strata conditions should be used to obtain the effectiveness of machine drivage on roadway deformation. However, if the magnitude of deformation of the roadway driven with machine and supported with the traditional system is within an allowable limit, the validity of using machine cutting can be found in the rapid drivage rate leading to the total cost reduction in formation and maintenance of roadway.

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Following in the first report which elucidated that feldspar (albite) was effectively removed from low grade Amakusa pottery clay by two-stage flotation in laboratory batch-test, continuous flotation has been applied to the process. The results are as follows:
1) The semi-batch tests, which were carried out before continuous flotation tests, indicated that each mineral was devided into two groups having the slow and fast flotation rates.
2) In the rougher stage of continuous clay flotation, concentrations of collector were higher than the values expected from the semi-batch tests and tailing flow rate of pulp remarkably decreased owing to discharge of froth. As a result, the residual mass ratios showed lower than the simulated value on the basis of the results of semi-batch tests.
3) In feldspar flotation, the residual mass ratios agreed well with the simulated ones because tailing flow rate of pulp did not decrease so much and the concentrations of collector were almost consistent with the ones in the semi-batch test.
4) The refractoriness of the products obtained by the continuous flotation was improved. It was verified that the continuous flotation process for the removal of feldspar from the low grade Amakusa pottery stone is technically feasible.

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Mineralogical properties of the kaolin mineral included in “oxidized zone” of Iriki kaolin clay deposits, Kagoshima prefecture, were studied in order to clarify the possibility of the utilization as a blending raw material for “White chinaware”. Dispersion and coagulation properties of kaolin clay were also analyzed to find out the optimum condition for removing the ferric and titanium oxides from the kaolin clay by means of a high gradient magnetic separator (HGMS). The experimental results were summarized as follows:
(1) X-ray powder diffraction analysis showed that main mineral compositions of kaolin clay were kaolinite and quartz and minor components were ferric oxide and anatase. EPMA analysis of the are rock revealed that ferric oxide was very fine particles distributed among kaolinite particles and most of anatase had the needle like shape. The minerals of finer particles than 3μm were mostly kaolinite and included a few amount of quartz, ferric oxide and anatase.
(2) Yield and TiO₂ content of the concentrate by HGMS test increased with increasing the matrix loading, however, Fe₂O₃ content did not change with matrix loading. Yield of the concentrate from the clay finer than 3μm increased 20% higher and the quality did not change as compared with the clay finer than 44μm.
(3) HGMS treatments showed that the change of the dispersant concentration did not affect the yield and Fe₂0₃ content of concentrate, but TiO₂ content of concentrate decreased with coagulation of kaolin clay. These phenomena seemed to be explained by taking account of selective coagulation of anatase particles.

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In the leaching process for the residue in zinc hydrometallurgy, most of gallium is concentrated into the solution together with zinc and sulfuric acid. Such solution is then neutralized with calcium carbonate till pH 4.0, thus forming the precipitates of gallic hydroxide and gypsum. In order to recover and utilize gallium from the precipitates, selective flotation of gallic hydroxide from gypsum has been investigated.
The floatability of gallic hydroxide was first examined using dodecylammonium acetate (DAA) and sodium dodecylsulfate (SDS) as a collector. Gallic hydroxide floated completely with SDS in the pH range of 4-7. On the contrary, it didn't float entirely with DAA in the same conditions. When the flotation was made in saturated solution of gypsum, both gallic hydroxide and gypsum floated to some extent with either of these collectors. As gypsum was quite floatable in these conditions, it was necessary to use some depressant for the selective flotation of gallic hydroxide from gypsum. Then, selective flotation was made for the mixture of gallic hydroxide and gypsum. It was shown that soluble starch and gum arabic were effective depressant for gallic hydroxide in DAA flotation.
Synthetic metallurgical process with water containing 100mg/l of gallium ions, 3700mg/l of sulfate ions and 621mg/l of calcium ions was neutralized with calcium carbonate from its pH 1.5 till pH 4.0. Flotation tests were conducted for the precipitates thus formed. Gallic hydroxide was effectively separated from gypsum with DAA collector when soluble starch or gum arabic was added as a depressant, and some 91% of gallic hydroxide was recovered in the tailing. Also, gallium was up graded from 1.65% to 14.73%.

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In order to analyze the reduction rate for the mixture of iron oxide and zinc oxide with CO-CO₂ gas mixtures, reduction experiments were carried out in pure hematite pellet and pure zinc oxide pellet in the temperature range from 973 to 1173 K. Experimental data for each reduction were analyzed in terms of the mixedcontrol kinetics based on the isothermal unreacted core model and the isothermal shrinking model, respectively. Then the rate parameters were determined. The results are summarized as follows:
(1) For hematite pellets the reaction rate constant k_C2 and the effective diffusivity D_e1 are expressed, respectively, by following equations: k_c2/10^-2m·s^-1=exp 16.65-120.0×10³/(RT) D_el/10^-4m²·s^-1=exp (8.553-9.646×10³/T).
The activation energy of the reaction was 120 kJ·mol^-1. The calculated reduction curves by using the rate parameters based on the unreacted core model are in satisfactory agreement with the experimental data.
(2) For zinc oxide pellets the reaction rate constant k_c1 are expressed by the following equation and the activation energy was 240 kJ·Emol^-1. k_c1/10^-2m·s^-1=exp 23.33-240.3×10³/(^RT)
The calculated reduction curves finely reproduced the experimental data. Finally, it was found that the overall rate is controlled by chemical reaction under the experimental conditions.

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Surface tension was determined for acidic zinc sulfate and copper sulfate solutions with the compositions corresponding to those of electrolyte solutions generally used in electrolytic production of zinc and copper. The solution composition was as follows:
Acidic zinc sulfate solutions,
H₂SO₄ (g/l), 150 and 200, ZnSO₄ (g/lZn), 0-80; MgSO₄ (g/lMg), 0-20.
Acidic copper sulfate solutions,
H₂SO₄ (g/l), 50, 150 and 200; CuSO₄ (g/lCu), 0-70; NiSO₄ (g/lNi), 0-20.
The temperature range was 25 to 60°C.
The following expression fits all the observed values of sufface tension with a standard deviation of 0.17 dyn/cm.
γ(dyn/cm) =75.30-0.153t+0.007 ([H₂SO₄]+[M]) t+0 (67) [H₂SO₄] +2.12 [M]
where t is temperature in °C and [M] is the total concentration in mol/l of the metal ions considered in this work,
[M] =[Zn] + [Mg] + [Cu] + [Ni]
The effect of addition of gelatin on the surface tension of the acidic sulfate solutions was also investigated at the gelatin concentrations up to 200mg/l. The surface tension markedly decreases with an increase in the gelatin concentration. However, the surface tension increases gradually with time after the addition of gelatin toward the values for the solutions without added gelatin. This rise in surface tension is more pronounced at higher acid concentration and at higher temperature and can be attributed to the progress of hydrolysis of gelatin in the acidic sulfate solutions.
Thiourea added in the acidic sulfate solutions was found to have no detectable effect on the surface tension of the solutions with and/or without gelatin added.

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A new process consisting of fractional crystallization and electrowinning from sulfate solution was proposed for the recycling of rare earth magnet scraps which contain about 30% of Sm or Nd and 50-60% of Co or Fe. Fundamental data for the recycling, the solubilities of Sm₂ (SO₄) ₃ in H₂SO₄-H₂O and CoSO₄-H₂O as well as the solubilities of Nd₂ (SO₄) ₃ in H₂SO₄-H₂O and Fe_SO₄-H₂O were determined in the temperature range 0 to 80°C. The results are summarized as follows: 1) In increasing the temperature, the CoSO4 and FeSO4 solubilities in water increase, while Sm₂ (SO₄) ₃ and Nd₂ (SO₄) ₃ solubilities decrease sharply. 2) From the results of X-ray diffraction and thermal analysis, the forms of equilibrating solid phases were identified as Sm₂ (SO₄) 3·8H₂O from 0 to 80°C, Nd₂ (SO₄) ₃·8H₂O within 0-80°C and Nd₂ (SO₄) ₃· 5H₂O at 80°C respectively. 3) In increasing the SO₄^2- (H₂SO₄, CoS0₄, FeSO₄), the solubility-[S0₄^2-] curves of Sm₂ (SO₄) ₃and Nd₂ (SO4) ₃ show the maximum value which shifts to higher SO₄^2-concentration with temperature increasing. It was presumed results essentially from the formation of RE (SO₄) +and RE (SO₄) ^2-complexes. 4) It seems possible to recover Sm Nd and Co from rare earth magnet scraps with sulfate fractional crystallization method by controling temperature and SO₄^2-concentration.

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Reduction smelting forming a soda base slag by addition of sodium salt is applied to the extraction of oxide ore or smelter recycles. To get a fundamental data on the reduction smelting of antimony, Na₂O-SiO₂ or FeOn-Na₂O slag was equilibrated with metallic antimony containing small amount of impurities such as Fe, As, Sn, Pb, Cu at 1423 K. Dependences of the antimony solubility in slag and the distribution ratios of impurities upon oxygen potential and slag composition were clarified.
The solubility of antimony in slag increases with increase of oxygen potential and the soda-ratio of nNa₂O/(nNa₂O+nSiO₂). The activity coefficient of SbO_{1, 5} (1) in the basic slag of high soda-ratio varies from 1 to 0.001 depending on oxygen potential.
Iron and arsenic are removable from crude antimony to soda base slag by control of oxygen potential and slag composition. While the acidic slag of low soda-ratio is suitable for removal of iron, the basic slag of high soda-ratio is effective to eliminate arsenic from crude antimony.

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