112 



FOYE. 



The phenocrysts of augite and zoned labradorite, Ab4oAn58 to Ab26An74, 

 are small and about equal in size (2 to 3 mm. in diameter). The 

 ground-mass forms about SO percent of the rock which is fresh and 

 above the average in weight. A few small vesicles are present. 

 The ground-mass is ophitic; it bears magnetite and a little serpentine. 

 The chemical composition is: 



SiOa 50.06 



AI2O3 19.38 



FeaOg 1.83 



FeO 5.54 



MgO 6.53 



MnO 0.47 



CaO 12.06 



NaaO 1.16 



K2O 0.93 



H2O (below 100°C) 1 . 14 



H2O (above 100°C) 0.37 



COo 0.31 



Total 99.78 



Specific Gravity at 20°C = 2.808 

 Analyst, L. F. Hamilton. 



Norm 



Quartz 2.88 



Orthoclase 5 . 56 



Albite 9 . 96 



Anorthite 44 . 76 



Diopside 12.36 



Hypersthene 19.60 



Magnetite 



Water . 

 (^0.>. . 



Total 99.49 



Its position in the norm classification is: — 



Class III Dosalane, 



Order 5 Germanare, 



Rang 4 Hessase, 



Subrang 3 Sodipotassic (unnamed). 



Washington, in Professional Papers, Nos. 14 and 28, of the U. S. 

 Geological Survey, reports no basalts having analyses similar to the 

 above. 



2. Hornblende Andesifr. The andesite was found as a boulder in 

 an agglomerate interljcdded with ash on Arawa Island, just west of 

 Yasawa-i-hui. This island lias an area of but little over an acre. 



The rock is light gray in color, with a brownisli tinge chie to weather- 

 ing. It has phenocrysts of hornblende in lath-like forms, 4 to 5 mm. 

 long. The zoned phenocrysts of andesine (Ab72 An28 to Abeo An4o) 

 are 3 to 4 mm. long and 2 mm. wide. The partly glassy ground mass 

 is greenish gray in color; its feldspar is oligoclase. The hornblende 



