The Hosokura Mine is situated at the eastern margin of so-called "green tuff region" in northeastern Honshu, and is one of the largest lead and zinc producers of fissure-filling vein type in Japan.
On the basis of the following geological features;
1) the location of the Hosokura mine in view of the regional geologic structure, 2) the relationship among the vein system, the areal geologic structure and the gravimetric anomalies, and 3) some characters of mineralization, which are represented by equal grade and equal Zn/Pb ratio contour maps, some hypothetical guides for exploration have been obtained.
They are summarized as follows;
1) the presumed location of a mine that is of fissure-filling vein-type in so-called green tuff region, 2) the presumed plane extent of the Hosokura mine, and 3) the most suitable level for exploration with regard to mineralization.

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As the result of the intensive exploration, based upon the studies of geological structure and mode of mineralization, more than ten new ore-bodies were discovered in the external zone around the known mineralized tracts of the Mozumi mining area of the Kamioka mines. At present the zone involves the following ore-bodies ; S No. 6 to 9, E No. 2 to 5, NW No. 1 and 2, N No. 21 to 23 and the Nakagoya-North. The discovery of these ore-bodies has brought about 2, 500, 000 tons of crude ores. In near future, another 4, 000, 000 tons of probable ore reserves may be expected.

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The Ryushoden mine is situated in the so-called "Tohoku Hokkaido Green Tuff Area" in the northernmost parts of Japan. The ore deposits are stratabound disseminated cinnaber deposits which occur in tuffaceous sandstone belonging to the Ryushoden formation of the Miocene Konomai basin.
Prospecting of the Ryushoden mine by the present owner, Hokushin Mining Co., Ltd., was initiated in November 1960, and thus four ore bodies have been discovered. Because of this successful exploration, the mine has become one of the leading mercury producers in Japan. The prospecting program has been carried out through the following four periods.
During the first period (1960-1962), the writers made geological and mineralogical studies on the known ore deposit of small scale and adjacent area. Consequently, the northern extension of No. 1 ore body was discovered in 1961. During the second period (1963-1965), the writers re-examined characters of "F₂ fault" with respect to the No. 1 ore body, and reached a conclusion on the F₂ fault to be of pre-mineralization. This judgment led the writers to the discovery of No. 2 ore body along the F₂ fault in September 1963.
The third period (1966-1968) was spent. to establish the exploration criteria, in summarizing all the available data of geological studies, geochemical and geophysical works, and operation research for drilling span. Some useful indicators was obtained through this work. They are ;
1) to trace the N-S main structure of the basement rocks,
2) to comfirm extension of the known ore deposits along the horizon of the conformable host rocks and also to find of siliceous rocks on the N-S structure,
3) to find gravity anomaly belts on surface,
4) to use geochemical mercury anomaly on drilling core, and
5) to apply operation research for drilling span to decide an area for prospecting and also mining limits.
On the basis of the above procedures, No.3 and No.4 ore bodies were discovered during the final period (1968-1970). The exploration criteria are so far valid for the ore deposits of the Ryushoden mine at this moment. An attension may be called on the criteria to be improved with further development of the new ore bodies.

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Thailand is now very famous for its.large tin production due to the development of many tin deposits in granites and its weathered derivatives accompanying kaolin deposits, especially in the Southern Peninsula of Thailand forming a main tin production area.
The tin-bearing granites, are probably of late Cretaceous age and called "Younger granite". They intrude into the rocks belonging to the upper Cambrian Phuket series consisting of slate, phyllite and quartzite. The distribution of individual granite body has northerly trend in Ranong Province. The tin-bearing granites include much variation of petrographic features due to those of grain size as well as the subordinate mineral species, such as a coarse-grained tourmaline granite, a medium-grained tourmaline granite 'and a medium-grained muscovite tourmaline granite, etc. They suffer intense alterations including tourmalinization, sericitization and kaolinization.
The kaolinization is probably due to remarkably developed weathering under the tropical climate condition, making the formation of placer-type tin and kaolin deposits possible. The primary tin deposits were formed in the granites by dissemination of cassiterite, accompanied by accessory amounts of ferberite (-wolframite), monazite, xenotime, ilmenorutile and spessartine, which are found in the tailing products of the dressing process of tin ores. The kaolin deposits have kaolinite as the dominant ore mineral accompanied by a subordinate amount of sericite.
The laboratory test for the separation of these accessory minerals and kaolinite group minerals was. successfully made. Cassiterite is concentrated at the heaviest part; while the other accessory heavy minerals remains in the tailing.
A rare mineral of ilmenorutile was identified with its microscopic character and X-ray reflection pattern. According to the results of the X-ray, D. T. A. and electron microscopic studies of them, kaolinite is almost pure and equigranular grains with hexagonal tabular form.
As compared with kaolinite from sedimentary origin (e. g. Ipoh, Malaysia), this kaolinite consists of various size of fine crystals because of its unsorted origin. The highest peak of the grain-size histogram is obtained at 5-7μ.

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