anthophylite (?) Schiller plates of a deep purple colour are 

 also present to some extent in the hypersthene. A large 

 chromite or picotite grain, together with a few small grains 

 of rounded irregular shape is also present. Oval areas 

 occur, composed at the centre of an aggregate of parallel 

 green fibres and surrounded by a ring of radiating green 

 fibres, probably chlorite. These seem to be the replace- 

 ments of original olivine crystals. (See fig. 11.) In certain 



SpS3« 



^At 



Fig. 11 — Pseudomorph after olivine in gabbro porphyrite. 

 of the phenocrysts of augite, usually those paler in colour, 

 there is present a granophyric intergrowth of pleonaste, 

 sometimes most beautifully developed. (See Plate 34, fig. 3) 

 In a very few instances green spinel is present merely as 

 simple grains. The ground mass of the rock is subordinate 

 in amount to the phenocrysts. It consists of a fine grained 

 aggregate of plagioclase witli a little augite. The plagio- 

 clase is rarely twinned well, and is not definitely determin- 

 able. A few grains develop pericline twinning on so fine a 

 scale as to resemble microcline. 



