g4 Vol. XLIII., Art. 6. — S. Tstiboi : 



them from each other. Poly synthetic twirming after (100) which 

 is said to be ^'ery characteristic of chno-enstatite*^ is entirely 

 absent in our clino-hypersthene. 



Augite is a light greenish variety. It is found very rarely as 

 microphenocrysts, but abundantly in the groundmass as one of the 

 essential ingredients, and ranges from nearly euhedral to anhedral. 

 Sometimes the mineral occurs in a thin rim around hypersthene 

 in parallel intergrowth. The common type of twinning after (100) 

 is often met with, while the intergrowth with plagioclase penetrat- 

 ing each other in cross is sometimes seen. 



Magnetite occurs in rather large euhedral crystals in the more 

 crystalline part, reaching as large as 0.06 mm. in diameter, while 

 in the less crystalline part it shows very often dendritic skeletal 

 forms. 



Apatite is almost absent, its needle with characteristic negative 

 elongation (0.02 mm. in length) was detected only in one instance 

 in thin section from tlie perci'ystallin'e part of the recent lava. 



Glass base is uniformly brown in thin section. Its index of 

 refraction wns measured with the powders from the more hyaline 

 part of the recent lava to be n- 1.593 — 1. 590. This high refractive 

 index shows the basic nature of the glass. 



Chemical Characters. — The chemical analyses of three of 

 the la VMS and one of the scoria» of the recent eruption gave the 

 followincr results :'^ — 



1) O. Andersex, "System Anorthite-Forsterite-Silica," Am. Jour. Sei. (4), Vol. XXXIX., p. 419, 

 1915. 



2) These analyses were made in the Geological Survey and were published by Okamuüa ia 

 Lis report on the recent eruj)tion {l.epoit Gtol Surv. Japan, No. 48, 1914j. 



