EAKLE. ROCKS FROM THE FIJI ISLANDS. 583 



VlTI Levu. 



Specimeus of eruptives were obtained by gift from three localities on 

 this island. 



Kai Vatu Lola. — Specimens of jasper, quartz, and the granite pre- 

 viously mentioned are labelled from this place, which is believed to be in 

 the central part of the island. 



The granite megascopically presents a white granular rock, having 

 plates of dark hornblende well disseminated through it. The structure 

 is hypidiomorphic graiudar, and the composition is essentially of plagio- 

 clase feldspar with green hornblende plates and quartz grains. Most of 

 the feldspar sections exhibit fine polysynthetic twinning combined very 

 often with Carlsbad twinning. The extinction angles on sections normal 

 to the brachypinacoid 010 vary from a small angle up to a maximum 

 extinction of 18°. The index of refraction of the sections showing the 

 larger extinction angles is slightly below that of the Canada balsam, 

 indicating albite as the feldspar, while oligoclase is also present, but not 

 so prominent. A few sections of orthoclase more cloudy in appearance 

 than the plagioclases occur, and also two or three sections of microcline 

 showing a beautiful grating structure. The feldspars are in general 

 quite fresh and free from inclusions with the exception of an occasional 

 apatite and zircon crystal. A few of the smaller sections possess good 

 crystal boundaries. 



Hornblende is abundant in plates with ends usually frayed out. Much 

 of it is altered to yellowish green chlorite and granular epidote and the 

 formation of some calcite. The fresh hoi'ublende shows strong pleo- 

 chroism. 



Quartz is not very abundant in the rock, and cannot be detected in the 

 hand specimen. A few basal and prismatic anhedrons are seen however 

 in the thin section as an original filling between the feldspars. Magnetite 

 occurs which is evidently titaniferous, as it usually has a border of grayish 

 leucoxene surrounding the grains. 



An analysis of this rock would doubtlfess show a large percentage of 

 soda in its composition because of the large amount of albite present, as 

 well as of oligoclase, and the small amount of potash feldspar. While 

 designated here as a dioritic granite, it might perhaps equally well be 

 considered a quartz diorite. It is the only one of the specimeus in the 

 collection which is not effusive in its origin. Wichman describes an 

 amphibole granite very rich in plagioclase from INEuanivatu Mountains* 



* Loc. c'lt., p. 8. 



