THE GREAT ERUPTION OF SAKÜRA-JIMA IN 1914. 191 



causing a maeroscopically saccharoiclal effects. It is an anortJiosite- 

 equic aient in lava. The anorthite shows no signs of plagioclase 

 twinning, polarizes in brilHant colors with closely packed banding 

 of spectrum colors on periphery, distincly seen in Figure 2 of 

 Plate XXI. The size varies from 0.15 to 1.50 mm. The only 

 other constituent is orthoclase (?) which fills, in patches {om?n.), 

 the interspaces left by the aggregates of anorthite (the black patches 

 in Fig. 2, PL XXI. and the dirty field in Fig. 8, PL XX.). The 

 grayish color of the orthoclase is solely due to the multitude of 

 pores as in the quartz of mylonitized granite. Birefringence and 

 refraction are lower than those of anorthite. Quartz, if present, is 

 not easily distinguished from others by ordinary method. Laceoix 

 mentioned the same blocks ejected from Martinique and 

 Santorin. 



This particular specimen of the enclave was qualitatively tested 

 by Kanai, of the Higher Agricultural College of Kagoshima, and 

 gave the following results : SiO-z very abundant, CaO and AIM 

 abundant, alkalies {KiOyNa-^O) moderate, Fe little, MgO none. 

 Presumably this white projectile is composed of anorthite mixed 

 with a subordinate quantity of orthoclase, as is proved by micros- 

 copic analysis. 



The ß type (PI. XXI. Fig. 5, PL XXII. Fig. 1) is a white disc 

 of 10 cm, with black banding tinged slightly green (Text-fig. 42). 

 It is rarely found and hitherto only in the east. It has a fine 

 granular porcelain-like appearance on fracturai surface, and the 

 mineralogical composition of cUopside-gabhro with aplitic texture. 

 Basic plagioclase forms an equigranular aggregate of subhedrons 

 and grains, some showing symmetric extinction at 40^, indicating 

 that we have before us either bytownite or anorthite. Another 

 granular component is anhedral diopside with augite-cleavage, zonally 



