Mot illog'ony of the Japanese Islamls. 5 



formed at liigh temperature, and, as we go downwards, the tem- 

 perature of tlieir formation is lower. Minerals having a high 

 position in the petrification order are spoken of as " of the higher 

 order of petrification." Not only does the order indicate the order 

 of the formation of the minerals, but also their position in certain 

 deposits. The liigher the order of petrification, the lower is the 

 position of the minerals in the ore-deposits, for it is natural that the 

 temperature of emanations in rock fissures should become higher the 

 lower we go. The I'eason of the constant association of quartz with 

 .gold, and the transition of quartzose gold ores into sulphides in the 

 bottom of mineral veins may be readily understood in the order of 

 petrification of emanations above cited. Lindgren^^ enumerated 

 persistent minerals according to their positions, ranging from the 

 contact metamorphic or igneous condition to the surface of the 

 earth, as shown in tlie following list, viz: — pyrite, chalcopyrite, 

 bornite, arsenopyrite, galena, zincblende, molybdenite, gold, 

 quartz, calcite, etc. The reader will easily recognize the essential 

 coincidence between my petrification order and the above list. 



In magmatic segregations found in Japan, only the first two 

 minerals in my petrification order occur, of Avhich chromite in 

 serpentine is the only one workable. Contacts constitute the best 

 reservoirs for all the magmatic emanations, and therefore various 

 minerals are found there. Of these minerals, magnetite, chalcopy- 

 rite, cobaltite, and sometimes gold are being worked. In mineral 

 veins which are located far from the source of the ore-bringer, the 

 temperature must be lower than in magmatic segregations and con- 

 tacts, and initial products such as magnetite and chromite can not 

 journey through so long a passage. Accordingly there occur only 

 pyrite and such minerals as are of a lower order than it, of which 

 the copper and gold ores are chiefly being Avorked. Ores occurring 

 as impregnations and replacements do not present many points of 

 difference from those in veins, but are very complex in their 

 composition; for all elements of the emanations are shut up in 

 them as in the case of contacts. This is especially true of replace- 

 ments, such as those in the Kosaka Mine. 



1) Lindgren : Ezonomic. Geology, Vol. II., p. 122, 1907. 



