ANDREWS: LIMESTONES OF THE FIJI ISLANDS. 43 



The phenocrysta are quartz orthoclase, plagioclase, and a little decom- 

 posed biotite. They are all more or less idiomorphic aud are more or 

 less corroded by the magma. They all contain inclusions which are 

 gaseous, glassy, or lithoid. Apparently there are no liquid inclusions. 

 The felspars are all clear and glassy and are distinguished from the 

 quartz and from each other by the nature of the twinning. The in- 

 clusions are more or less symmetrically arranged. 



There are three or four decomposed basal sections of biotite. These 

 contain grains of magnetite. 



19. Mango. Specific gravity, 2.75. Olivine anamesite. 



The plagioclase is of two generations, — the older in tabular, cleaved, 

 and corroded crystals, showing zoning in places, and the newer crop is 

 in the form of acicular microlites felted together. The olivine is very 

 abundant and in places shows large idiomorphic grains. Only slightly 

 serpentized. The augite is scattered through the rock in almost color- 

 less granular aggregates. Magnetite occurs as irregular grains in great 

 abundance. Apatite is also present in small stumpy prisms, especially 

 as inclusions in the older felspars. The groundmass of the rock is 

 crypto-crystalline and colorless. 



Professor David of Sydney University also describes a section from 

 Mango. 



20. Mango. Olivine basalt. 



This olivine basalt taken from the beach at Mango has in thin section 

 a very fresh appearance. It is formed of irregular granules of olivine 

 fairly free from decomposition, though slightly serpentinized at the edges ; 

 clear phenocrysta of plagioclase and smaller felted crystals with small 

 augites and numerous magnetites in a crypto-crystalline base. 



The magnetites are all bounded by sharp edges, and are remarkably 

 free from traces of decomposition. 



The whole rock has a decidedly fresh appearance. 



The Limestones of Fiji- 

 Viti Levu. 



The Older Limestones of the Main Island. — This is a compact limestone 

 of bluish-yellow color, and possessing a dip of 50°. It appears to be 

 connected with the dolomites of the upper river. It will be remembered 

 that this rock underlies the shelly limestone of the Thuvu-Singatoka 

 area. 



