NOTES ON SOME IGNEOUS ROCKS OF JAPAN 

 Ratios calculated from the norms are as follows: 



575 



By the quantitative system, A, D, E, and F would be classified 

 under the name andose and G under akerose. 



From the tables given above, it is clear that the rocks from 

 Fukae differ from normal basalt, in containing a high percentage 

 of alkalies in proportion to the silica contents, especially of soda, 

 forming normative andesine Ab s8 An 42 , which is slightly more calcic 

 than the modal plagioclase. Though the alkali-feldspar is not 

 present as a recognizable mineral in the first type (Bomb) of the 

 first rock group, its molecule is to be looked for in the glass-base. 

 In the second and third type, the alakli-feldspar is seen in the modal 

 state. The chemical resemblance between the rock of Fukae, A, 

 and the olivine-basalt from St. George's Head, E, is very close. The 

 differences between them are lower potash for orthoclase, slightly 

 higher soda for plagioclase and higher normative ilmenite in the 

 Fukae rocks, compared with the olivine-basalt, of St. George's 

 Head. Generally the rock is characterized by properties mineral- 

 ogically and chemically intermediate between the mugearite, G, 

 described by Harker, and the olivine-basalt described by Card, 

 though it is very near to the last rock, and it differs from shosho- 

 nite described by Iddings in being dosodic. 



The rock from Madara-shima, D, differs slightly from the Fukae 

 rock in the lower value of magnesia and in higher percentages of 

 silica and potash, and of alumina which increases the normative 

 anorthite. It has a close resemblance in chemical characters to 

 the orthoclase-bearing doleritic basalt, F, from Croobyar Creek, 

 New South Wales, described by Card. 



