324 



ferro-magnesian minerals are scarcely represented occur in several 

 localities. The plagioclase is often seen to be idiomorphic with respect 

 to quartz and orthoclase, and the two last-mentioned minerals 

 frequently occur in micro-pegmatitic aggregates. The normal rocks 

 are augite-biotite-granites or augite-granitites. They are unlike any 

 other granites known in the British Isles. The more basic rocks, 

 which are somewhat limited in their distribution, have decided affinities 

 with the so-called syenites of Charnwood Forest. These rocks have 

 already been described. Original hornblende has not, however, been 

 detected in the Cheviot rocks. The only hornblendic constituent is 

 a pale green fibrous uralite which has been occasionally developed at 

 the expense of the augite. 



Scotland. The granites of the Southern Uplands are intrusive 

 in lower Palaeozoic strata and produce marked contact alteration. The 

 more important masses occur in Kirkcudbrightshire. That of Dalbeattie, 

 which forms a part of the Criffell mass, is greyish white in colour, and 

 may be described as a granitite or hornblende-granitite containing 

 much sphene. The plagioclase frequently shows a zonal structure and 

 is often idiomorphic with respect to quartz. No detailed descriptions 

 of the other masses have as yet been published. A brief account of 

 their mode of occurrence and of the contact metamorphism which 

 they produce will be found in the Survey publications/ 1 ) 



Granites abound in the Highlands of Scotland, but much work 

 will have to be done before we are able to separate the different 

 masses according to their relative ages and petrographical characters. 

 Some of these are intimately associated with the crystalline schists 

 (e.g., those of Aberdeen), others are of latter date (e.g., those of Ben 

 Nevis). The grey granites of Aberdeen have been referred to by 

 Professors HAUGHTON and HEDDLE^) and by Mr. PHILLIPS.^ 

 They are composed essentially of orthoclase, microcline, a lime-goda 

 felspar (oligoclase according to Professors HAUGHTON and HEDDLE), 

 and two micas. 



They are, therefore, true granites in the German sense. Apatite 

 and zircon also occur, and the inclusions in the dark mica are 

 surrounded by the usual dark border. The microcline structure is 

 beautifully shown in many of the felspar sections. 



Hair-like crystals (? rutile) occur in the quartz. Mr. PHILLIPS 

 records the occurrence of garnet and sphene. Inclusions and patches 

 of dissimilar character are comparatively rare in these granites. Those 

 described by Mr. PHILLIPS appear to be inclusions of foreign rocks 

 rather than concretionary patches. They are sometimes welded to the 

 enclosing rock; sometimes coated with a layer of mica. Nests of dark 

 mica may, however, be occasionally observed in the Rubislaw quarries. 



(1) Explanations to sheets 4 and 9 of the Scotch Survey. 



(2) Proc. Roy. Soc., Vol. XVIII., p. 313. 



(3) Trans. Roy. Soc. Edin., Vol. XXVIII., p. 265. 



(4) Q.J.G.S., Vol. XXXVI. (1880), p. 11. 



