In this paper the outline of the newly developed Yaso Mine of the Sumitomo Metal Mining Company is described. The mine is sitnated on the mountainous district, 60km south of Wakamatsu in Fukushima Prefecture.
Many veins and some massive deposits are known, and some of them have been rapidly developed in these three years. The are have been produced by shrinkage and horizontal cut and fill stoping method. The are consists of chalcopyrite, pyrite and quartz essentially with, minor amounts of sphalerite and galena. The are contains 1.6% Cu and 5%S in average.
The 250t mill was built in Dec. 1954 and was started with good results. Two minerals, chalcopyrite and iron pyrite, are concentrated differentally by flotation with extraction 95% Cu and 45%S.
The concentrates containing 26%Cu and 45%S respectively are shipped to the Shisakajima Smelter of the same company. Since April 1955 350tons of are have been treated daily with the, same results.

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We measured the strain of drilling rod as method of studies on the impact mechanism of drill piston and drilling rod.
The results showed that an elastic theory applied to explain the impact mechanism of drill piston and drilling rod instead of Newton's law of impact applied in the case of rigid body, and it is proper to be considered that the rod is a medium of propagation of elastic waves. The figures of momentum only calculated from both theories are approximately same in the short rod but they are not same in the long rod.

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This paper gives a mathematical formula of the influence factor of the surface-subsidence in the horizontal or inclined strata the dip of which is smaller than 20°, as the generalization of Bals's formula.
And inducting the conception of the influence factor of horizontal movement, a mathematical formula of the influence factor of horizontal movement is given.
The author applicates these formula to make the nomographs of the influence factors of rectangular goaf (stoping area) and attempts to make easy and simple the pre-counting of mine subsidence.

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We studied the cyaniding of the roasted residues from Herrenshmidt Roaster and that of complex silver sulfides which belong to the stibnite group. The results of studies were as follows: 1) IIn, the straight cyaniding of roasted residues, the cyanide extraction of gold was about 74 per cent. and that of silver was only 32 per cent. 2) Artificial miargyrite ore destroyed much cyanide and extraction of silver was about 4 per cent.. The volatilized roasting for cyanide treatment was little effective. The roasted products having been treated with caustic soda solutions, the extraction of silver increased to 88 per cent. 3) The cyaniding of tetrahedrite silver ore and its roasted products was not satisfactory. As for the cyaniding of the roasted products, treated with caustic soda solutions, the higher the roasting temperatures, the less the cyanide extraction of silver became. It was found that tetrahedrite silver ore sintered at higher temperatures (above 900°) would not decompose by heat treatment with caustic soda solutions. 4) The roasted residues from Herrenshmidt Roaster having been treated with 8-10 per cent. caustic soda solutions at 80°-100° for 6-8 hours before starting cyanide treatment, the extraction of gold and silver increased remarkably. 5) Being treated with soda sulfide and sulfuric acid, antimony leached in the caustic soda solutions could be recovered as antimony trisulfide.

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