Gold mining industry began in 7 th century with a considerable result from the technical point of view. After flourishing times of 200 years, it gradually declined in prosperity on account of domestic warfares until Muromachi era. Gold mines were again. worked in 16th-17 th century, because foreign methods of newer mining technic were imported. Excavation of gold are in Japan is so old that mines which are easy to discover and work are nearly exhausted in bonanza. Therefore ores remained are in general unknown ores without outcrops or low grade ores in depth or are bodies which are difficult to smelt. At present there is very small quantity of pure gold in Japan, some 100 tons or so. But there are 3, 000 pits which are recorded in outputs of gold since the discovery of gold are in Japan and there are 800 mines which have had actual production of gold in these 20-30 years. The writer assumes the gold are reserves about 500 tons, but their, grade is very low. Gold ores in quartz vein had the leading position in the Meiji era (1905±). But gold. ores by hydrothermal process through volcanic activity in and after Tertiary were discovered in Konomai, Takatama, Kawazu, Takeno and Tainohu Mines in Taisho-Showa era (since 1912). Gold resources in sulphide are have recently been collected and unknown ores in depth are being discovered with hopeful prospect of success.
The true structural boundary of the Pacific margin should obviously have a border of considerable width surrounding it, yet all influencing the basin itself, which in turn must react upon it. For instance, the Austro-asiatic continental block is the true margin of the Pacific basin. This paper deals with the geologic characteristics of the Japanese archipelagoes and the southern islands, facing the ocean depths ; and the andesite line which curves strongly to the west toward the Halmahera Is. The simatic of the Pacific bottom should have moved between New Guinea and the Palau-Marianen Is. forming an asymmetric echelon structure, the portion of which is alluded to the Halmahera Is. It is on this frame that geologic layers of New Guinea are extending far through Halmahera under the Philippine sea and Palau Is. group For instance the crystalline schist of Japan Is. of New Guinea is connected with those of Japanese Is. of the Palau group. On the other hand, the outer zone of Japanese Is. which consists of crystalline schist, Mikabu, Chichibu and Akigawa series, forms monocline dipping north. On the whole, it is alluded to form an inclined syncline along the Median line, the south wing of which is postulated to extend for under the South Japan Sea. The southern limit of the South Japan Sea may be Karenko (Formosa) Sulpher Is. fault line, which corresponds to the north latitude 24, and to the Neo-Wallace Hosokawa line biographically. The submergence of the South Japan Sea may have occurred due to the depression of the outer zone which was thrust by the pushing out of the Loochoo arc from the northwest
The so-called “Akashiro” & “Aoshiro” silica-stone of good quality is an important material for five brick which is at present used for Siemens-Martin furnaces in Japan. For this purpose, such a conditions as follows of silica-stone are necessary : (i) SK>33 (ii) no rapid expansion or shrinking (iii) intense resistance against slag. This report treats yielding places, distribution, chemical and mineralogical composition, texture, and origin of the silica. stone in Japan. The writer considers that the silica-stone is a sort of methamorphic rocks by hydrothermal process. Ore reserves of the silica-stone is large enough to answer for 20 years' supply, if present yield is to continue. But it is necessary to explore the are of Tohoku (North East Japan) & Hokkaido in view of transportation conditions.
Goto archipelago is situated 50 miles west of Nagasaki harbour, consisting of five larger islands together with numerous islets (about 200). The writer describes at first natural environments, such as climate, oceanic influence, coastal topography etc., then he discusses the economic life of inhabitants to which social organization under the special conditions has influenced. He concludes that the daily life of the inhabitants is a continuation of struggles against natural environment and they remain in miserable and defeated circumstances.