GEOLOGICAL OBSERVATIONS IN FIJI. 125 



Its position in the Norm classifieatioii is, tluMTi'ore: — 



Class III Salfeinane 



Order o Gallare 



Rang 4 Auvergnase 



Subrang 3 Auvergnose. 



Basalts erupted from Kilauea, Hawaii in May, 1883, have a com- 

 position very similar to the basalt described above, (\yashington, 

 1903, p. 337). 



IS us id. 



1. Andcsite. Andesite forms glassy flows, 8 to 10 feet thick, just 

 northeast of the town of Susui. The flows strike about E-W and dip 

 30° S. They are vesicular near their top and elsewhere have a platy 

 structure. 



The rock is slate-black in color but often has a reddish tinge due to 

 the formation of hematite. It is massive and porphyritic. The 

 phenocrysts of andesine, AbeaAnsr to Ab59An4i, and augite are small 

 (1 to 2 mm. in diameter). 



The ground-mass is composed of minute laths of feldspar in a glassy 

 matrix. 



2. Basalt. Interbedded flows of basalt form a point at the extreme 

 eastern end of Susui. The flows dip 25 to 30° S. W. The specimen 

 to be described was collected near sea-level. 



The fresh rock is slate-gray in color, massive and porphyritic. It is 

 holocrystalline and very fine-grained. 



The phenocrysts visible in the thin section are feldspar, olivine, and 

 augite. The olivine phenocrysts are most abundant, though the feld- 

 spars are more distinct in the hand specimen. The feldspars are 

 labradorite, Ab4oAn6o to AbosAnys. 



There is very little oli^•ine in the pilotaxitic ground-mass and the 

 approximate proportions of feldspar and augite are 60 to 40. 



Munia. 



Olivine basalt. Massive flows, interbedded with ash and agglomer- 

 ate deposits, form the abrupt slopes of the eroded crater of jNIunia. 

 The writer collected five specimens from the flows and from boulders 

 in the agglomerates. They differ only in structure. The rock to be 



