466 THE GEOLOGY OF THE NEW HEBRIDES, 



Large inclusions, chiefly of glassy materials, are a feature of these 

 bigger individuals. The second generation is represented by the 

 microcrystalline reticulated laths of the groundmass and, only to 

 a very limited extent, as a marginal zone around the earlier 

 crystallisations, from which it is distinguished by its less basicity. 

 Pyroxene is a light yellow augite developed chiefly as tiny 

 grains (microgranulitic) in the interstices of the felspar laths of 

 the base. Large idiomorphic crystals up to 2 mm. diam. are 

 present only to the extent of about 3 %. Olivine phenocrysts up 

 to 3 mm. diam. are a prominent feature even in the hand-speci- 

 men, not only on account of their size, but for the fact that 

 they are stained reddish along the cracks by deposition of iron 

 oxide. The clear olivine itself has a slightly pinkish appearance, 

 probably indicating a high iron percentage. Magnetite is present 

 in grains derived from both crystallisations."^ It is represented 

 in the former to the extent of about 2 % by individuals up to- 

 0"5 mm. diam.; in the base it appears as tiny particles scattered 

 about indiscriminately. Apatitu in microscopic needles is present 

 adhering in radial fashion to the tiny magnetite grains of the 

 groundmass. A little apatite is included in the first generation 

 individuals. Secondary minerals : Serpentine and other fine 

 fibrous secondary minerals of a greenish colour, are developed to 

 a slight extent, filling up small crevices. 



Order of consolidation — 



Fels. I Mag, 



Mag. I Apat. 



Oliv. 



Pyr. 



Pyr. 



Fels. 



Analysis (see appended table). 



Nam e. — Olivine basalt j^orphyrite. 



Jevons's nomenclature. — phyri-pilotaxi-oli-gahbromicrite. 



* In such a rock as this it is quite uncertain how much of the magnetite 

 is primary and how much has been developed by later crystallisations and 

 recrystallising processes. 



