GEOLOGICAL OBSERVATIONS IN FIJI. 131 



The position of the rock in the Norm cUissification is: — 



('hiss II Dosalane, 



Order 5 Germanare, 



Rang 3 Andase, 



Subrang 4 Anciose. 



Kambara. 



Olivine BasaJt. A thick dike of oHvine basalt has broken through 

 the Hmestone at the northwestern side of Kambara and stands up in 

 the hill Xdelai Yaloi. Several specimens of the rock were collected 

 of which three were studied. One of these was collected at the lower 

 contact of the dike, another was taken from the upper contact, while a 

 third came from a zone some 15 to 20 feet from the upper contact. 



The general characteristics of all these rocks are the same. They 

 vary, however, in their texture and in the amount and variety of their 

 phenocrysts. Near the upper contact the rock is very vesicular and 

 has large vesicles 15 to 20 mm. in diameter. Here olivine phenocrysts 

 are abundant l)ut augite and feldspar phenocrysts are lacking. To- 

 wards the center of the dike, the feldspar and augite crystals increase 

 in abundance and the vesicles become smaller. 



The basalt from the top of the hill of Ndelai Yaloi will be described. 

 The contact is 15 to 20 feet south of the summit. 



The rock is drab-gray in color, very fine, even-grained and some- 

 what vesicular. Phenocrysts of olivine 5 to 8 mm. in diameter are 

 seen but the small augite phenocrysts are less distinct. 



Feldspar occurs only as fine needles in the ground-mass. It has 

 the composition of basic andesine, Ab6oAn4o. 



The olivine phenocrysts are euhedral, but the augites are irregular 

 and resorbed. 



The intersertal ground-mass contains olivine, augite, and feldspar. 



Serpentine, kaolin and hematite have developed by weathering. 



The analysis of this rock is: 



SiOs 45.63 Norm 



AI2O3 15.56 



FeaOs 3. 12 Orthoclase 6.67 



FeO 10.81 Albite 11.00 



MgO 8.64 Anorthite 33.36 



MnO 0.24 Diopside 20.38 



