GEOLOGICAL OBSERVATIONS IN FIJI. 127 



Its position in the Norm classification is: — 



Class II Dosalane, 



Order 4 Aiistrare, 



Hang 3 Tonalase, 



Subrang 4 Tonalose. 



The lavas of Bandai San, Japan, approach the composition of the 

 basalt from Thikombia and also a lava from a volcano on New Britain 

 Island, Pacific Ocean. The Bandai San lavas are described as an- 

 desites and undoubtedly the rock just described has a composition 

 more closely allied to an andesite than to a basalt but since its feldspars 

 are largely labradorite it is called a basalt. The lavas of Crater Lake, 

 Oregon, are also similar to the rock here described. 



2. Vesicular Basalt. This specimen was broken from an angular 

 boulder in the agglomerate which constitutes a small cape near the 

 middle of the south shore of Thikombia-i-lau. 



The fresh basalt is a very spongy, vesicular type with fine vesicles. 

 It is dark gray in color and porphyritic. 



The feldspar phenocrysts are 2 to 3 mm., occasionally 8 to 10 mm., 

 in diameter. They are zoned and the zones are frequently outlined 

 by glass inclusions. They have the average composition of labra- 

 dorite, Ab45An55 to Ab4oAn6o. The augite is a diallagic variety. 



The ground-mass has a hyalopilitic texture. Feldspar and augite, 

 in the approximate proportion of 70 to 30, and abundant magnetite 

 are present in the glass. 



Kanathea. 



Olivine basalt. Three specimens of basalt from Kanathea were 

 examined. One came from sea-level at the northeastern side of the 

 island; another was collected at an elevation of approximately 20 

 feet within the central valley; and a third was taken from the summit 

 of a high cliff at the southern side of the central valley. All three 

 have approximately the same composition. A typical specimen will 

 be described. This rock occurs as a sill intruded into the agglomerate 

 near sea-level. 



It is very dark gray, massive, holocrystalline, and fine-grained. 

 The augite and olivine phenocrysts are 4 to 5 mm. in diameter; 

 the zoned labradorite phenocrysts (Ab57An43 to Ab43Ano7) are smaller. 

 The ground-mass is diabasic. 



