=40 GRANITES OF THE SOUTH OF SCOTLAND. 



and perhaps zircon. Lenticular masses or nests of black mica occur, 

 in which are crystals of white felspar, quartz, and sphene. On the 

 south shore of Loch Sunart the Strontian granite is more micaceous 

 and hornblendic, and contains large masses of hornblende rock. 



Galloway Granite. Mr. Irvine remarks of the mass of granite 

 called Cairns More of Fleet, which is one of the three large granitic 

 bosses of Galloway, that its colour is grey, shading in places to pink, 

 and its texture coarse, so that on the top of the hill crystals of quartz 

 and felspar are two inches long. The granite usually consists of 

 quartz, orthoclase, plagioclase, and black and white mica ; but some- 

 times the mica may be almost replaced by hornblende, and frequently 

 the quantity of quartz is small. The black mica, called Lepidomelane, 

 is the most common, but in Cranmer, Craiglowrie, and Craigherron 

 Hills a white mica occurs, probably Margarodite. Quartz frequently 

 occurs in hexagonal prisms. No mass of fine-grained granite occurs 

 in the area, but dykes and veins of elvanite are found all through the 

 heart of the granite, and in the surrounding metamorphosed area. 

 The rock consists of white orthoclase felspar, with a little mica, iron 

 pyrites, and quartz. Occasionally, at the circumference of the granite, 

 the rock passes into a compact felstone, with some crystals of horn- 

 blende. Many patches of altered stratified rocks are caught up in the 

 granite ; the largest, in Blair Buie's Hill, is 600 feet long by 150 feet 

 broad. 1 



The Granite of Loch Ken 2 consists of pink and white orthoclase 

 and plagioclase felspar, quartz, mica, some hornblende, and a little 

 iron pyrites. But the quartz may disappear entirely, and hornblende 

 often replaces the mica. Crystals of sphene abound near Loch Aber- 

 loch. Near the margin the rock is foliated, and then hornblende is 

 most abundant. Veins abound on Bennan Hill west of Loch Ken. 

 Near the margin of the granite, felstone dykes are frequent. 



Arran. 



General Features. The Island of Arran has been very often 

 described by eminent geologists. Jameson, MacCulloch, Necker, 

 Murchison and Sedgwick, Oeynhausen, Von Dechen, and Ramsay 

 have all written ably on the inexhaustible subject of this little world 

 of geological phenomena. The leading features of Arran are its moun- 

 tainous and truly Alpine scenery in the northern extremity, and the 

 elevated plateaux of its southern portion. These latter are generally 

 partly of syenite, partly porphyry, partly basalt, with many basaltic 

 dykes and dykes of pitchstone passing through the red sandstone 

 strata. 



Granite occupies the central district of the northern half of the 

 Island of Arran, and is especially seen in the mountains. It is sur- 

 rounded by clayslate, and schistose rocks. Sir Andrew Ramsay 



1 Mem. Geol. Surv. Scot., Sheet 4, 1878, p. 18. 



2 Ibid., John Home in Explanation Sheet 9, 1877. 



