106 FOYE. 



Pebbles in the conglomerate near Suva harbor are essentially 

 similar, though richer in quartz. 



The quartz has a wavy extinction due to strain and is often quite 

 brecciated. 



The feldspars are zoned and give evidence of intermittent growth. 

 Their composition ranges from basic ollgoclase to acid andesine 

 or from AbvsAno^ to AbesAus?. No orthoclase was found in the 

 rock. 



The biotile is chestnut brown in color. 



The hornhlevde is a common variety, pleochroic, colorless // X, faint 

 yellow // Y, and greenish yellow // Z. 



The rock is very slightly altered and has a hypidiomorphic, granular 

 structure. Its order of crystallization is : — 



magnetite, 



biotite, 



hornblende, 



plagioclase, 



quartz. 



The chemical composition of the rock approaches that of a granite, 

 and undoubtedly granites are associated with it in the field; but the 

 dominance of andesine and the absence of orthoclase, lead the writer 

 to designate it as tonalite. , 



Chemical analysis gave: — 



SiO. 70.00 



Ti()2 0.30 Norm 



AI2O3 14.72 Quartz .31 .38 



Fe.,03 1 .36 Orthoclase 10.01 



FeO 2.28 Albite 31.44 



MnO 0.04 Anorthite 16 96 



MgO 1.37 ("oruiKhun .51 



CaO 3.58 Hypersthene 0.04 



NaaO 3.70 Magnetite 



KiO 1 . 68 llmenite .• 



H2O 0.50 Apatite 



P2O5 _(V0(; ^^■ater 



99.59 

 Specific gravity at 20°C = 2.(575 



