502 B. K. N. Wyllie & A. Scott— Plutonics of Garahal Hill 



Eeckoning the hornblende as equivalent to pyroxene, we may state 

 the rock-types represented, as follows: — 

 Pyroxenite. 



(Diallage-enstatite.) [(Gabbro) + Norite.] 



Lherz elite and Wehrlite. 

 (Di. En. 01.) (Di.Ol.) 



Pyroxene-peridotite . 

 (01. with little Di. or En.] 



Picrite and Enstatite-picrite. 

 (Di.Ol. (Di.En. 01. 



Felspar.) Felspar.) 



Olivine rock. 

 We have not found any rock rich enough in felspar to be called 

 )ro, though the felspathic veins in davainite come very close to 

 that. A norite has been recorded at locality iii (Map, Fig. 1), but 

 this is a hybrid rock and will be mentioned later. 



Davainite. 



We have now to substantiate at greater length our contention that 

 the brown hornblende here found is altered diallage, and, consequently, 

 that the rock we designate as davainite is the equivalent of the 

 pyroxenites. There are two possibilities: (1) the change may have 



Fig. 2. Sketch-map showing the occurrence of Davainite at locality ii. (See 

 Map, Fig. 1, ante, p. 500.) 



occurred during cooling, and may denote a ti'ansition temperature 

 below whicli hornblende is stable, and above, diallage; (2) the 

 change may be due to some kind of annealing of the diallage rocks 

 by the later diorite magma, which, as we have noted, is in intimate 

 contact with the davainite at locality ii.^ (See Map, Fig. 1.) 



^ By annealing we mean reheating to a temperature which is lower than the 

 melting-point of pyroxene, but which lies in the region where hornblende is the 

 stable modification. 



