ng composition : — Augite 



Plagioclas 

 Ilmenite 



100 



the periods of consolidation overlapped greatly. On the 

 whole the order appeared to be ilmenite, felspar, augite. 

 As this rock showed a marked tendency to segregation of 

 the pyroxene, the slide may not be quite typical. It is 

 probably lower than the average in felspar. 



The spinel-bearing gabbros bear features of the greatest 

 interest which will be described later. They are of two 

 classes, those without granophyric intergrowths, some of 

 which have a slightly banded structure, and which have in 

 general crystallised in the scheme below :— 



Pleonaste I 1 



Hypersthene i I 



Diopside diallage I ! I 



Plagioclase I — I 



and secondly, the rocks with a granophyric intergrowth of 

 pleonaste and pyroxene. 



In the pyroxenites and peridotites, picotite is always the 

 first formed mineral, with olivine slightly earlier than 

 pyroxene. The grains are about a millimetre in diameter, 

 some rocks however have a grain size more than twice this; 

 a variety is found in a dunite with finely "granular olivine 

 about '2 mm. with phenocrysts of enstatite and rarely 

 olivine I mm. in diameter. The strained nature of the 

 enstatite crystals and the approximate parallelism of 

 adjacent granules of olivine indicate that this is a normal 

 peridotite which slight shearing has rendered granulitic in 

 those portions composed of the brittle mineral olivine. 

 (See Plate 31, fig. 2.) 



