GEOLOGICAL OBSERVATIONS IN FIJI. 135 



coid and arc distinctly culicdral. Olivine is present, in scattering 

 crystals which haAc largely altered to serpentine. 



The texture of the ground-mass is hyalopilitic. 



5) Olwinc Basalt. A central, N.-S. ridge extends through the 

 island of Ndavuni, which lies north of the island of Ono. At the 

 western foot of "this ridge, near the center of the island, the specimen 

 of basalt was collected. 



It is fresh, greenish black, holocrystallinc and very heavy. Pheno- 

 crysts of black augite, 5 to 7 mm. long and 4 to 6 mm. wide, are 

 abundant. Phenocrysts of olivine are less plentiful. 



In thin section, small phenocrysts of feldspar are seen to be most 

 abundant. They have the composition of labradorite, Ab45An55. 



The structure of the ground-mass is pilotaxitic; minute feldspar 

 needles form a mat in which rounded crystals of augite and magnetite 

 occur. The proportion of feldspar to augite is approximately 2 to 1. 



Solo Rock. 



A7idesitic tuff. A single point of rock less than a hundred yards in 

 diameter rises within a circular reef, just north of the Great Astrolabe 

 reef which surrounds Kandavu. On this rock the Solo light-house is 

 situated. The rock is but 8 or 10 feet above the sea. Several speci- 

 mens, all tuffaceous and andesitic, were collected. Augite, basic 

 andesine, and rare biotite appear in the lava of the fragments. 



PETROLOGY OF THE FIJI ISLANDS. 



As stated previously, the igneous rocks, collected during the expedi- 

 tion, are not sufficiently numerous or characteristic to serve as a basis 

 for a full petrologic discussion. By comparing personal observations 

 with those of other writers, an attempt will be made, however, to state 

 a few generalizations. 



Association of Pluto7iic Rocks. 



Gabbros and diorites have been described from Vanua Levu, and 

 gabbros, diorites, granites, and foyaites, from Viti Levu. Sufficient 

 field-work has not vet been done to show the exact nature of the 



