On Mineralogenesis Appeared in the Main Lodes of the Nakase Mine, Hyôgo Prefecture, Japan.

The ore deposited in this mine are naturally considered to have been produced through certain processes during four main periods denoted as P I, P II, P III, and P IV representing respectively a different sort of mineralization. The main lodes containing gold, silver, and antimony ores are comprised principally in those produced in P III correlated to Plio-Pleistocene, being furthermore subdivided into S 1 and S 2 in stage.
Twenty five kinds of ore minerals have so far been described, among which some are found included commonly in all of the lodes formed in each period and the others only in those originated during specific periods.
To be noted is that the main lodes representing P III have been excavated along the main gallery, revealing a sort of distorted échelon-like structure in their distribution. Veinlets composing this kind of the lodes have elaborately been scrutinized on their polished specimens and thin sections principally under the microscope so as to establish the mineralogenetic sequence. As was expected, the results obtained seem too complicated to be put in good order. It however is proven to be valid that variation of the mineral-izer in property with time is evidently recognized either as decrease of arsenic or as increase of antimony in the lodes produced at S 1 and S 2 stages, while variation in mineralic constituents is recognizable in the earlier to later veinlets as is shown in such sequence as arsenopyrite-berthierite-freibergite-stibnite. Each lode revealing discrepancy in arrangement is mineralogically somewhat different from one another, whereas a single lode indicates almost no vertical variation resulted from difference in temperature of mineralization and in mineral assemblage. It thus follows that the lodes under consideration might have been deposited from low-temperature hydrothermal solution displaying no remarkable difference in property on each level. On the other hand it is also to be taken into account that variation of property of the ascending solution might have taken place with time or with characteristics of fissures and that country rocks embracing the lodes might have provided the spaces for deposition of ores without any notice-able effects.