In the double side-polished thin sections, the details of the internal structure in wolframite can be observed in transmitted light. The microscopic study of wolframite is effective to reveal the history of the wolframite mineralization. The internal structures in wolframite can be divided into four categories. There are the homogeneous structure (Zone A), the oscillatory zoned structure (Zone B), the irregular structure (Zone C) and the banded structure (Zone D) from the core to the margin of the crystal. This zonal sequence can be interpreted as the formational sequence.
Quantitative chemical analyses of wolframite show that its composition varies considerably within a single crystal. This compositional heterogeneity in wolframite interferes with the accurate evaluation of the compositional variation of wolframite throughout the deposits by bulk analysis. Taking observations of the internal structures into consideration, the compositional variation of wolframite throughout the deposits is revealed. Wolframites, in the up-per and the western parts of the No. 7 Vein which is the champion vein in the Takatori deposits, are dominantly composed of Zone A and rich in Mn WO₄ contents. In contrast to this, wolframites in the lower and the eastern parts are dominantly composed of Zone B and rather poor in Mn WO₄ contents.
The internal structure and the composition preserved within each wolframite crystal, and their distribution pattern in the No. 7 Vein are reasonably explained by the interpretation that the crystallization of wolframite in the upper and the western parts of the No. 7 Vein is ealier than that in the lower and the eastern parts.

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The geology of southwestern Hokkaido is characterized by intensive volcanisms of Miocene to Plio-Pleistocene age. The studied area, eastern margin of Lake Toya, is one of the centers of the volcanic field where Miocene andesitic and dacitic lavas and pyroclastic rocks (Osarugawa formation), Pliocene dacitic tuff (Kitayuzawa formation) and plagioryolite and Plio-Pleistocene andesite lavas are distributed. The volcanisms subsequently caused a concealed alteration zone, and mineralization such as Date Au-Ag-Cu-Pb-Zn deposits, Kamaya iron-roseki deposits and many other sulfur-iron deposits of Plio-Pleistocene age. The concealed alteration zone and alteration halos associated with the mineralization were examined in terms of field observations, mineralogical investigations and K-Ar ages determination. The results obtained are as follows:
(1) The, concealed alteration zone, Kamaya iron-roseki deposits and sulfur-iron deposits were generated by Pliocene plagioryolite and Plio-Pleistocene andesite volcanisms. The Au-Ag-Cu-Pb-Zn mineralization of the Date deposits was genetically associated with quartz porphyry intrusive to Miocene pyroclastic rocks.
(2) The concealed alteration zone is divided into five zones: mordenite zone (mordenite+clinopt-ilolite+mont-morillonite+mica/montmorillonite mixed layer minerals+kaolinite), laumontite zone (laumontite+Ib chlorite+mica/montmorillonite mixed layer minerals+1M mica+calcite), wairakite zone (wairakite+laumontite+IIb chlorite+1M·2M mica+anhydrite), mica zone (1M·2M mica+IIb chlorite+epidote+anhydrite) and pyrophyllite zone (monoclinic pyrophyllite+mica/montmorillonite mixed layer minerals+kaolin).
(3) In the Date Au-Ag-Cu-Pb-Zn deposits, the alteration characterized by 1M mica+nacrite+ dickite+mica/montmorillonite mixed layer minerals+dioctahedral chlorite at the center, while by montmorillonite+chlorite/smectite mixed layer minerals at the margin. K-Ar age of a mica-bearing altered rock was determined to be 5.2 Ma.
(4) The alteration zone of the Kamaya iron-roseki deposits is observed in plagioryolite and underlying Miocene pyroclastic rocks, The mineralogy changes from the center outwards as follow: triclinic pyrophyllite→monoclinic pyrophyllite→kaolin+dioctahedral chlorite→mica.
(5) The alteration zones of sulfur-iron deposits occur mainly in Pliocene dacitic tuff and overlying andesite lavas. The alteration minerals are dominated by kaolinite, dickite, nacrite, montmorillonite, dioctahedral chlorite am chlorite/smectite mixed layer minerals with disseminated pyrite and marcasite.

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Geological, structural, chemical and radioactive studies were conducted on the radioactive chalcedony vein at El Missikat area, in the central part of the Eastern Desert of Egypt.
At surface, the radioactive anomalies were recognized sporadically. An exploratory mine was done at Wadi level to follow the distribution of radioactivity and uranium mineralization at the western part of the chalcedony vein. Contrary to expectation the radioactive anomalies were observed to increase slightly in length, and downwards as well as at the alteration zone on both sides of the vein. The results obtained will lead necessary exploration works in the depth to pursue the extension of radioactive zones.

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