24 Vol. XLIII., Art. 5.— T. Katô: 



times entirely or partially replaced by calcite. Quartz of secondary 

 infiltration is occasionally fonnd as patches and veinlets. 



Effusive Liparite. Besides the felsitic rocks in the form of 

 dykes, a liparite as an effusion is extensively developed on the 

 ridge between Akénobé and Mikobata. It covers the dioritic rocks 

 which constitute the main bulk of tlie mountain under considera- 

 tion. It is gray or brownish gray in colour, compact in texture, 

 and contains abundant phenocrysts of feldspar and quartz. 



Under the microscope, the groundm iss consists of light brownish 

 glassy matter contaminated with abundant globulites and margalites, 

 and contains more or less feldspar microlitcs and minute flakes of 

 biotite. Fluidal structure is not conspicuous. As phenocrysts, quartz, 

 feldspar and biotite are abundant, ranging from a microscopic size 

 to 2 or 3 mm. in length. Quartz occurs as bipyramidal crystals 

 and fragments, and is often magmatically corroded. Feldspar occurs 

 in the form of tabular crystals and also as corroded fragments. 

 Both sanidine and plagioclase are present, but the former is more 

 common. Biotite occurs in hexagonal plates, usually full of 

 magnetite grains. 



Porphijrites. Dykes of exceedingly altered porphyrites with 

 macroscopic phenocrysts of feldspar occur here and there in the 

 vein district under consideration. For instance, the dyke exposed 

 across the Higashiyama vein, striking E.-W. and dipping steeply 

 toward S., belongs to this category. It is entirely altered to a 

 gray earthy matter, but still retains a porphyritic structure. A 

 similar porphyrite dyke is found in the underground workings in 

 the Daikoku adit in the Daijukô area, striking N. 30° W. and 

 dipping steeply toward S. W. These rocks are often so altered 

 that they may be crushed to powder between the fingers, and 

 consequently it is impossible to make thin sections. 



