The writer reports here his studies of the fundamental characters of the three kinds of ore from the so-callad Kuroko deposits with special reference to the ores of the Hanaoka Mine. The effects of secondary sulphide enrichment are usually so strong on the deposits of this type, that black copper ores have been formed in many ore bodies of the Kuroko mines. These ores have been often called confusingly "proper. Kuroko ". For the present purpose these secondary apparent Kuroko ore are not treated in this paper.
At Hanaoka the Kuroko deposit consists of three kinds of ore, i. e., siliceous ore, yellow ore and black ore. It is very difficult to define the representative of them. From many chemical analyses of the ores, the writer calculated statistically the mean valne of the ratio of Cu, Pb and Zn of each kind of ore. The following are the results : siliceous ore… Cu : Pb : Zn=77 : 4 : 19, yellow ore… Cu : Pb : Zn=56 : 5 : 39, black ore… Cu : Pb : Zn=10 : 20 : 70.
The three kinds of ore in one ore body are found generally in the order of black ore, yellow ore and siliceous ore from the upper to the lower parts of the deposits. The grade of copper becomes gradually lower at the lower parts. This tendency of decrease of copper content, from upper to lower, is reverse to the change of the ratio of Cu : Pb : Zn. This presents a problem on the dressing of ore from the black ore deposit, from which it is said to be very difficult to get good recovery of copper at present.
The three kinds of ore were formed in order of siliceous ore, yellow ore, and, lastly, black ore. In other words the ore rich in chalcopyrite crystallized first, sphalerite-ores, next and ore rich in galena, last. Considering from data of chemical analyses of the various kinds of Kuroko ores., there seems to be some limit on the ratio of the constituent minerals such as chalcopyrite (Cu), sphalerite (Zn) and galena (Pb) in the Kuroko deposit.

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The ore deposit of the Kawayama mine is comprised of veins and several veinlets of pyrrhotite, chalcopyrite and sphalerite. The veins and veinlets dip at a low angle. As seen from structural features, mine-ralizing solutions seem to have ascended-along a thrust plane. Though the thrust plane is nearly parallel to the bedding planes, it crosses the folded strata of a syncline in the country rock. Consequently the country rock forms an abnormal strike zone along the thrust. This abnormal disturbance is, therefore, a good indicator for prospecting. Also by tracing the cross thrust zone, the extent of ore deposit can be expected. The extension already prospected is 600 metres on the strike side and 1, 000 metres in the dip side.
Lenticular voids inclined at low angles and resulting from thrust movement were probably the most favorable places for the mineralization. This idea of mineralization accords very well with the field data. By making a vein contour map, it may be possible to find more hidden deposits along gently dipping thrust zones.

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In recent years, there has rapidly developed in Japan a strong tendency to follow the detailed yet composite American methods of geological study with the result that most mines have commenced to take up basic research and study along these lines.
The principal approaches in the study of ore genesis are (1) through "structural control" and (2) through "hydrothermal alterations on mother rocks".
In both these approaches, the ultimate objective lies in investigating the structure of the ore body, how it came to be formed in the country rock, and to determine its origin by correlation of mineralization eras through interpretations made of systematic mapping of detailed and minute observations of geological phenomena observed in rocks containing the ore body.
The only difference in the two approaches is that one is dependent upon dynamic causes, the other on petrology. In both cases, the common objective lies in the study of the character of the country rocks in relation to the passage of mineralizing solutions.
The study of rock conditions in relation to emplacements of various ore bodies, being extremely important in prospecting, now appears to be steadily heading in the direction of structural control and in general there still seems to be a lack of interest in conducting these studies from the aspect of alteration in country rock.
In most veins, unlike conceptions held in the past, it is now believed that at the time of the formtaion of the ore body the immediate alteration of the country rock is limited to the very small area along the fissures in which mineralizing solutions ascended.
The alteration of great masses of tuff and shale to the extent that it looks like liparite which is explained as having been caused by the action of large quantities of non-metalliferous hydrothermal solutions which had ascended before the introduction of minerelizing solution. Immediately after the alteration of the country rock, fissures were formed in the altered strata as they were then very susceptible to cracking. The ore bodies were then formed by the ascension of mineralizing solutions along these fissures.
Regional alteration of the country rock is a phenomenon that is the result of the action of ascending hydrothermal solutions which are the precursor of mineralizing solutions. However, as fissures are easily formed in altered rock, in a broad sense, ore deposits could be found in areas of altered rock:
Alterations in country rock assume different forms depending upon the nature of original rocks and the hydrothermal solutions.
Likely areas for prospecting can be discovered by detailed surveys of these alterations. Such studies are especially very beneficial in the explorations of mines at the initial stage.
Examples of notable discoveries in absolutely virgin lands from the above idea are illustrated by the discovery of the group of rich ore veins at Japan's representative gold mines, Takatama and Taio.

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Results of a study of the fundamental philosophy and methods of mining geology made during two trips to North America and Europe which afforded the author opportunities to visit and see 8 countries, 32 mines, 9 universities, 4 research institutes, 7 governmental organizations and about 135 geologists; are briefly summerized.
Importance of a broad knowledge of geological principles and basic common sense in mining geology; neccessity of exact, detailed observations in field work, the consideration of all the possible theories or hypotheses which can explain a set of observed facts, and recognition of the objectives and the basic philosophy of the profession, are emphasized.
Various guides and methods used for ore search are classified and tabulated according to time relations to ore deposition.

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After summarizing the uses, world output, stockpiles and national resources of sulphur, the sulphur position of Japan and the outlook for the future are briefly explained.

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