412 MR. G. BARROW OX THE MOINE GNEISSES [NOV. I904, 



bands, though considerable sliding may have taken place along the 

 greasy chlori tic parting-films. The belt within which this structure 

 occurs commences at the Tilt Valley, on both sides of the Tarf, 

 and stretches to the foot of Sron na Macranach. It will be 

 described in detail in the [Survey memoir on the district. 



Aberdeenshire Area, west of the Lochnagar Granite. 



The feature of this area, on the whole, is the perfection with 

 which the parallel structure is shown in the field, especially in 

 stream-sections ; the bauds are perhaps thicker than in the GariT 

 area, and they have a singularly-massive habit, owing to which 

 they may be described as of the ' niassive-pavernent ' type. These 

 massive pavements are admirably shown in the bed of the Geldie 

 above its junction with the Dee, where the river runs approximately 

 parallel with the strike. The dominant type of gneiss is grey, and 

 highly crystalline. Granulite and quartz-bleb structures are common 

 in many of the rocks, and they contain, on the whole, little white 

 mica. The biotite varies : sometimes it is normal haughtonite, but 

 more often it is of the reddish-brown type. Garnet occurs in micro- 

 scopic sections more frequently than the external appearance of the 

 rocks would lead one to expect. Plagioclase-felspar is far more 

 abundant than microcline, though here again there is one horizon 

 at which the latter is fairly abundant. Three types are worthy of 

 special reference. The first is a banded grey gneiss (8512), in which 

 Dr. Teall noted a Hue specially rich in iron-ore and zircon, clearly 

 indicative of original bedding and parallel to the colour-banding : 

 it is a typical granulite, with no trace of quartz-bleb structure. 

 The second is remarkable for the number of small pink garnets in 

 it, which enable the band lo be easily identified (8510). Like the 

 ' Blotch-liock ' of the Struan area, this little garnet-band has been 

 met with again and again over the area west of the Cairngorm 

 Granite, thus indicating that the whole group was originally of no 

 great thickness. The third type is a pink-edged epidotic gneiss 

 containing much microcline, which, though present over a limited 

 area, is abundant close to the margin of the granite, and specially 

 so near AConadh Mor, just inside the boundary of Inverness-shire. 

 A typical specimen (8519) is almost identical with (8518) from 

 the Allt Unich, south of the Geldie, which, on account of its 

 importance, will be referred to again (see p. 436). 



Area flanking the Dee above liraemar. 



In and about the Allt Unich. just mentioned, a considerable 

 portion of the Moine Gneisses is highly quartzose, and diners 

 marked^ from the typical grey- and pink-banded rocks, which are 

 here present only in subordinate quantity. This is due to the fact 

 that the flaggy gneisses are here largely composed of the Central- 

 Highland Quartzite, exhibiting many of the curious structures so 

 characteristic of the Moine Gneisses. Although these quartzose 

 rocks possess a flaggy aspect on the whole, it is not so marked as in 



