178 



ART. 3. — B. KOTÔ: 



intratellnric olivine was 

 resolved^^ into iron ore 

 and liypersthene (Text-fig. 

 40), and, chemically speak- 

 ing, olivine is equal to 

 iron oxide plus liypers- 

 thene. At times pseu- 

 dopodiform iron ore is 

 simply left, forming the 

 coi'e of the hypersthene- 

 aggregate (Text-fig. 40). 

 On another occasion, feld- 



spar laths enter into the pjg 40.— Hesorbecl olivine with pseudopodiform iron 



composition, building up °^^' ^""'"''^'^ ^^ hypersthene crystals in the 



^ o ± marine lava of the eastern field. 



micronoritic patches (oli- 



vine-norite) and motex. Lastly, an isolated anhedron of olivine 

 makes its appearance, and in tliis case it is not easy to discrimi- 

 nate this mineral fi'om tabular hypersthene. 



The groundmass is always of minute fabric and hyalopihtic, 

 being built up of prismoids or microlites of augite with a subordinate 

 quantity of feldspar laths and magnetite grains in bi'ownish glassy 

 base. See PI. XIX. Figs. 3, 4, 7 and 8. The color of the lavas is 



1) According to Bowen and Andersen ('The Binary System MqO — SiO^', Am. Jour. Sei., 

 1914, p. 499), olivine crystals may be resorbed during the normal course of crystallization as a 

 simple result of cooHng, and they inferred the formation of reaction-rims of enstatite around 

 the crystal to the same cause. The change of forsterite to clino-enstatite is said to take place 

 at about 1,557°C. 



As the oUvine sometimes appears associated with feldspar making micronoritic motex, as in 

 the historic Salmra-jima lavas, any motion, whether upward or downward, of the crystals in 

 magma can not be totally denied, as was demonstrated by Bowen (' Crystallization-Dififerentia- 

 tion in Silicate Licpiid,' klein, (1915), pp. 175 to 191). 



In the present case, we have to do with a ferriferous complex system, and the remarkable 

 pseudopodiform iron ore forms the transitional zone between the secondarily formed pleochroic 

 hypersthene aggregate and the resorption-rest of an iron-rich olivine. 



