The mode of origin of this rock is not clear. It seems 

 most probable that it resulted from the solidification in a 

 dyke of a mixture of two partially crystallised magmas. 

 The presence of brown spinel with felspar, of large diallage 

 crystals and granophyric phenocrysts are all unusual 

 features. The rock may be termed a hypersthene gabbro- 

 porphyry. 



Pijroxenites. 



A diallagite (see fig. 16) occurs which is composed almost 

 entirely of diallage with a minor amount of enstatite. The 

 enstatite occurs in rounded undecomposed grains, is 



H 



A- 



Fig. 12. — Diallage with enstatite and picotite. 

 the earliest product of consolidation. Moulded on the 

 enstatite, but not poikilitically enclosing it, the diallage 

 forms l;iriM>i>l;it y crystals about four millimetres in diameter. 

 It is pale brownish-green in colour in the section and with- 

 out noticeable pleochroism. It is polysynthetically twin- 

 ned parallel to 100, and contains finely laminar inclusions 

 of hypersthene parallel to the clinopinacoid. Schiller 

 inclusions are not well developed, but a few irregularly 

 oxide-filled cavities occur in bands, and the cleavages often 

 appear to be a little darkened by inclusions. A very few 



