NOTES ON SOME IGNEOUS ROCKS OF JAPAN 



573 



anhedrons 0.35 mm. in diameter. The apatite is noticeable in 

 elongated prisms. 



The most finely grained variety is from Uramino-taki. It is 

 light gray, compact with a few vesicles, and nonporphyritic, some- 

 times with nodular olivine. There are groups of scaly, blackish 

 brown mica in the vesicles. 



Under the microscope it is almost holocrystalline and granular. 

 The mineralogical components are the same as in the previous 

 variety, with a small quantity of biotite, which usually occurs in 

 cavities. The biotite is reddish brown and strongly pleochroic. 

 Its apparent optical angle (2E) varies between 37-5° and 29. 5 . 



Fig. 10 



Fig. 11 



Chemical characters. — Of the first group of rocks a complete 

 analysis was made of the first type (Bomb) and two partial analyses 

 of the second (B) and third (C) types, by K. Yokoyama. Of the 

 rocks of the second group a complete analysis of a specimen (D) 

 collected from Marada-shima was made by T. Ono. 



The three analyses A, B, and C of the first group show a close 

 relationship in chemical characters, notwithstanding they have 

 different mineralogical components due to their crystallinity. For- 

 eign rocks that have a close resemblance in chemical characters 

 with the rocks of this group are olivine basalt (E) and orthoclase- 

 bearing doleritic basalt (F) of New South Wales, described by 



