108 EOYE. 



Three varieties are known. They are very dissimilar in appearance, 

 due to recrystalUzation and crushing. 



Variety 1, a glassy, slate-black type, is the freshest of these rocks. 

 Grains of quartz and feldspar occur in a glassy, somewhat spherulitic 

 ground-mass. The quartz phenocrysts occur as amoeboid, resorp- 

 tion forms. The feldspar phenocrysts are slightly zoned and average 

 oligoclase in composition. 



Variety 2 of a light gray color has similar phenocrysts, but its 

 ground-mass is entirely recrystallized. The spherulitic forms are 

 sometimes discernible but often the quartz fibers have enlarged them- 

 selves, forming distinct crystals. There is also a semblance of myrme- 

 kitic structure as reaction rims about the large quartz phenocrysts. 



Biotite is found in scattered bits through the rock. 



Variety 3, a light yellowish-gray rock, has undergone a considerable 

 amount of shattering due to pressure. It is practically the same as 

 variety 2. Its yellowish tint is due to a large amount of epidote scat- 

 tered through, and veining, the ground-mass. The spherulitic struc- 

 ture is still preserved. 



4). Feldspar Porphyrite. The rock to be described occurs as flows 

 overlying the gabbro back of AVaimbasanga, Singatoka river. It 

 represents the first period of andesitic activity in Viti Levu. 



The porphyrite is dark, slate gray in color, holocrystalline, and very 

 fine-grained. Only occasional small phenocrysts of feldspar (2 to 3 

 mm. in diameter) are visible. They are indistinct, since they have 

 the same color as the ground-mass. The rock appears fresh in the 

 hand specimen but under the microscope is seen to be much recrystal- 

 lized and metamorphosed. Considerable deposits of chalcopyrite 

 are associated with the rock. 



Augite may have formed a part of this rock at one time but no trace 

 of it is now present. Actinolite is found in felt-like masses throughout 

 the rock and occurs as needles in the feldspar, clouding the crystals. 



The ground-mass of the rock is a complex of fibrous actinolite with 

 laths of labradorite, Abso Anso, and grains of epidote and magnetite. 



5) Olivine Basalt from the Tamavua River. Basaltic boulders 

 occur in the conglomerate which forms the basal member of the 

 coastal-plain series along the Tamavua river, near Suva. As basalts 

 cut this series farther west, it is considered that the rock here 

 described belongs to an earlier date than the last basaltic erupti(Mi 

 and is probably contemporaneous with the second andesitic period. 



The basalt is greenish black in color, compact, and recalls a por- 

 phyritic diabase. 



