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



the junction is plain, bvit on the other side it is obscured in every 

 instance by peat, though tonalite is exposed in mass close by and 

 intersects both the others in dykes and strings. 



The predominant type among the ultrabasic rocks is a pyroxenite, 

 with large bronzy diallage crystals which often weather out like 

 phenocrysts. Olivine is seldom absent ; it occasionally equals the 

 pyroxene in amount; and in places we find veins of y)ure serpentine, 

 representing the end product of this replacement. AH inter^iediate 

 stages are found between pure olivine (serpentine) rock and pure 

 pyroxenite. In one place an olivine-bearing rock is found forming 

 a vein 6 inches thick in a pyroxenite. 





V 



■X'"' . ■'■ s 



BeinnOarnhain 



'# \S^ 5c«/.5f Cafi _ 



a^' 



// 05'A"^uV^ Caracal 



/fBeiLf /f Schist Cafiy ^ 

 / { Daifihain ' ' 



\. 1 



P E. h^ 

 - /ILochX o*^ • / 







lE^ V HorrvUendiCe 

 I'v-I Tonaiite 

 PTTI Diorite 

 \^} U/Crabasic l^ocKsit 

 rs~\ MicaSchjsCs 



Oara 



Fig. 1. Sketch-map of the basic and ultrabasic rocks of Garabal Hill. Scale 

 1-7 inches = 1 mile. Note : 2' marks the area mapped by Teall & Dakyns 

 as peridotite, but the only evidence of peridotite that we could find was 

 some scattered boulders. 



A rock of entirely diiferent appearance occurs in large masses at 

 locality ii (see Map, Fig. 1) and in little strings at Loch Garabal. 

 This is composed of glossy coal-black crystals of hornblende of 

 a granular texture, with grains varying up to ^ inch in diameter. 

 At locality ii (see Pig. 1) this rock is found always intervening 



