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34 GRANITES OF SCOTLAND. Chester. 1 It is of a greyish colour, and generally porphyritic. Strontian, Argyleshire. Medium-grained grey granite, consisting of quartz, oligoclase white felspar, and black mica in abundance. 2 Island of Arran. The central group of mountains of this remarkable island, rising at Goat Fell to an elevation of 2875 feet, is composed principally of granite of two varieties, the coarse-grained and the fine-grained, formed probably at successive periods. In composition, however, they are similar, being formed of white orthoclase, a triclinic felspar pro bably oligoclase, quartz, and a little black mica; the quartz is very abundant. 3 Isle of Midi, &c. This island produces fine pink and red granites, which are now largely worked by the Scottish Granite Company. From the Ross of Mull it was proposed to obtain a monolith, to be erected in honour of the late Prince Consort, in Hyde Park. 4 The rock consists of pink orthoclase, a little mica, and much silica. Granite is also obtained from Portsoy, in Banffshire ; Dalmore, Sutherland ; Oban, in Argyleshire ; High Rock, Breadalbane, Perthshire ; and Tiree, in the Hebrides. 1 Mr. R. Hunt, Mineral Statistics, part ii. 1858, p. 273. 2 Brit. Assoc. Rep. 1863, p. 62. 3 This determination of the composition of the Arran granite has been kindly communicated to me by Mr. S. Allport, F.G.S. 4 Descrip.sGuidc to the Museum of Prac. Geol. p. 18 (1867).