1862.] HAtJGHTON GRANITES OF IRELAND. 409 



VI. Glenveagh. — Fine-grained gneissose granite : — 



(a). Quartz ; scarcely visible, grey. 



{b). Felspar ; wliite, sugary, facets rare, and when they do occur, semi- 

 transparent — probably oligoclase. 

 (<?). Mica; perfectly black, high lustre. 



VII. Poison Glen. — Medium-grained granite : — 



(a). Quartz ; grey, not prominent. 



lb). Felspar ; pink, in large crystals (^ in. by \ in.), semitransparent, 



predominant ; orthoclase. 

 (c). Mica ; jet-black, bright lustre. 



Vm. Poison Glen. — Coarse-grained granite. 

 {a). Quartz; conspicuous, grey. 



{b). Felspar; pink, in large crystals (^in. by :|in.), transparent, 



bright calcspar lustre, set in a paste of quartz and pinkish felspar. 



(c). Mica ; an occasional speck of green mica, probably not \ 'per cent. 



IX. Boocharry Bridge. — Medium-grained granite, tending to become porphy- 



ritic. 

 {a). Quartz. 



{b). Felspar; orthoclase, pink, in ^in. crystals, 

 (c). Felspar ; oligoclase, grey, in \ in. crystals. 

 {d). Mica; black, in small grains or specks, and in small quantity. 



X. Barnesmore Gap. — Coarse-grained, reddish granite, of platy structure, one- 



inch slabs. 



(a). Quartz ; very prominent, grey, occupying a surface only inferior 

 to the red felspar. 



{b). Felspar ; pale red, uniform in texture, with some well-developed 

 cleavages, not very brilliant. 



(c). Mica ; green, very compact, with few leaves, passing into chlorite- 

 earth: this chloritic earth covers the joint-surfaces (-^ in. to 

 ■Jg. in.), and is visible in all such partings. It is very difficult 

 to distinguish the green mica from hornblende. 



XI. Arranmore Island, — Porphyritic granite ; felspar predominating. 



(a). Quartz ; easily visible, abundant, grey. 



\b). Felspar ; reddish, in distinct crystals (^ in. to ^ in.), cleavage-planes 

 distinct, with bright lustre, semitransparent. 



(c). Mica ; black ; when seen on the edge, it resembles hornblende, of 

 which, however, there is not a particle in the rock: facets of 

 mica difficult to see, but having a very brilliant reflexion ; sub- 

 ordinate to both the quartz and felspar. 



XII. Tory Island, — Coarse granite, almost entirely composed of quartz and fel- 



spar, platy structure, one-inch slabs. 

 {a). Quartz ; conspicuous, crystals (-^ in.), grey. 



{b). Felspar; uniform red, with cleavage-planes of dull lustre, orthoclase. 

 (c). Mica ; greenish, sometimes white, in occasional very small plates. 



XIII. Ardara. — Coarse-grained gneissose granite : — 



{a). Quartz ; small grains. 

 (b). Felspar ; pink orthoclase 1 • , 

 \c). Felspar,' ^ey oligoclase } ^ lumpy masses. 

 (d). Mica; black, in large quantity, giving a gneissose appearance to 

 the rock. 

 Sphene occurs disseminated in small crystals. 



XIV. Dunlewy. — Consists of quartz and felspar, intimately blended together, 



and very similar in colour, whitish grey. In this paste are numerous 

 crystals of felspar (orthoclase), with definite (^ in.), lustrous, smooth 

 faces. Also occasional stains of greenish mica, looking like chlorite, 

 and small crystals of garnet. This granite occurs immediately be- 

 eide the limestone marble of Dunlewy quarry. 



