In sulphide deposits, generally, various sulphide minerals occur in massive or crystalline aggregates showing the relations of intimate paragenesis, and these minerals usually contain small amounts of selenium as their minor constituents.
It is a significant subject from a view point of economic geology to clarify the relations between the selenium content in various sulphide minerals which exist in the sulphide deposits and their mode of occurrence.
In present work, as a portion of these problems, the manner of distribution of selenium in several sulphide minerals which coexist in one hand specimen and show the relations of intimate paragenesis was mainly studied. And furthermore, it was examined whether selenium distribution in given minerals can or cannot be utilized as a geological thermometer when the formation-temperatures of minerals should be discussed.

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The ore deposit in Hatano mine belongs to the so-called “Kuroko” which are found in dacitic tuff or dacitic tuff-breccia of the Miocene. It is considered that the ore deposit was not formed at the present place but carried from somewhere in view of the distribution of the out-crops, the size and shape, and the character of the ore. That is, some ore bodies of “Kuroko” were broken by the volcanic action of dacitic rocks and transported with its mud-flows to the present situation.

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Primary pyrogenetic anhydrite which occurs in volcanic rocks has not been described, except for the anhydrite from Himeshima lava. Recently, the writer found and identified the anhydrite developed in the groundmass of olivine basalt from the Rishiri volcano, Hokkaido.
With regard to the genesis of the anhydrite, there is difference in opinion whether the anhydrite from Himeshima occurred as a phenocrystic (Kawano 1948) or as a groundmass mineral (Taneda 1949). The writer's studies on the anhydrite from the Rishiri volcano lead to the conclusion that this mineral was formed at the deuteric stage in the crystallization of the olivine basalt.

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