\ 2 Iwasaki : 



schists, the Sarnbagawan Series of Prof. Koto.^^ '^'hey are also 

 sometimes met with in the Paleozoic formation. As mother 

 rocks, basic rocks such as chlorite schist'^ and graphite schist are 

 the most favorable; serpentine is often found near the beds. 

 P^^'ite beds occur in the crystalline schists in nearly concordant 

 stratified form, cutting them crosswise in a few instances. The 

 pyrite beds consist of an intimate admixture of pyrite and chal- 

 copyrite. They are so compact that these two minerals can only be 

 distinguished from each other under the microscope after polishing, 

 •or in a few cases by the naked eye. According to Sakawa,^^ 

 the pyrite in the ore is usually in rounded grains, but sometimes 

 it is crystallized, when it attains 0.7 cm. in diameter. The 

 interspaces between the pyrite grains are filled with massive 

 ■chalcopyrite, which often enters even into the cracks of the 

 former. 



Pyrite beds sometimes form lenticular bodies or rounded 

 nodules. When they are found in tlie decidedly younger forma- 

 tion, i. e., the Paleozoic, they are usually roundish. The 

 structure of the pyrite beds in the so-called crystalline schists is of- 

 ten very complex. In the central portion, there are very rich 

 ■copper ores containing rock fragments, the outline of which is 

 either rounded or indented. On one or both sides of the rich zone 

 of the pyrite beds, there are found highly contorted ores, with 

 regularly stratified schists on their outer sides. These contorted 

 ■ores constitute the " shear zone " of Sakawa. 



From the facts above stated, and after very careful examination 

 •of a great many pyrite beds in Japan, he comes to the conclusion 

 that they are bedded veins of epigenetic origin. In my opinion, 

 however, the original form of the pyrite beds must have been that 

 of replacements Ijrought up in different successive periods. After 

 their deposition, a strong mountain-making force flattened them 



1) Koto "On the »o-called Crystalline Schists of Chichibu." Jour. Sei. Coll. Imp. Univ. 

 Tokyo, Vol. IL 



2) It is said that greater part of the so-called chlorite schist near the pyrite lieds is 

 amphibole-schist. 



3) Saka-v\'a : "Report on Cufriforous Pyrite Beds." Bull. Imp. (leol. Stin: Japan, Vol, 

 XXII., Xo. 1. (Japanese). 



