424 MR. G. BARROW ON THE MOINE GNEISSES [Nov. I904, 



the entire area, the Quartzite varies little in appearance and com- 

 position, and can be divided up into three parts, as follows : — 



(a) The fine white edge of the Quartzite, characterized by its 

 whiteness and its generally-fine grain, and usually containing but 

 little felspar. There is often present, however, a considerable 

 amount of unevenly-distributed pyrites, which, on decomposition, 

 imparts a rusty -brown aspect to this portion of the rock, and this 

 rusty aspect is even more characteristic than the unaltered white 

 colour. It cannot be too clearly understood that this is the only 

 margin of the Quartzite ever met with in the whole of the area under 

 discussion ; the reverse side, whether the top or the base, is never 

 seen. 



(b) The Quartzite, with dark lines of heavy minerals. — This part 

 contains a little more felspar than the last, although still practically 

 white. The fine dark lines in which the heavy minerals occur 



ndicate the bedding ; at times they show that the rock w r as 

 originally false-bedded. 



(c) The porous Quartzite. — This portion of the rock, which 

 commences some 6 or 8 feet from the outer margin, must have been 

 coarser originally, and contains more felspar ; at times it is 

 markedly felspathic. Owing to the indestructible nature of the 

 quartz, the felspar in an exposed face weathers out completely, 

 leaving a number of small holes in a homogeneous mass of quartz, 

 and imparting to this weathered face its typical porous aspect. 



The white edge of the Quartzite can be recognized in almost 

 every clear section, south of Braemar, where the junction with the 

 other members of the series is exposed. In what may be con- 

 veniently termed the type-locality, it occurs close to the roadside 

 north of Coldrach. The other parts of the bed may be seen 

 by ascending almost any of the quartzite-mountains in the neigh- 

 bourhood. 



2. The Parallel-Banded Series. — Immediately next the 

 white edge of the Quartzite is a rock composed of a few thin, 

 yellowish, quartzose bands, separated by pale, cross-cleaved, 

 micaceous films : obviously a passage-rock. This is succeeded by 

 greyer material, still in alternating layers of more siliceous 1 and 

 more micaceous composition, the latter again often cross-cleaved. 

 In addition, the face of the micaceous bands is often covered with 

 small spots or projections, proved in many cases to be minute 

 garnets. As we recede from the main Quartzite, the micaceous 

 material darkens in colour, and becomes more like the Dark Schist 

 above ; moreover, it exceeds the grey siliceous material in amount. 



The section here seen differs from the typical Honestones in 

 the greater proportion of shaly material between the more 

 siliceous bands in the original rock. Moreover, this softer material 

 contains much of the dark dust and clastic chlorite characteristic of 

 the horizon next above. The parallel-banded or passage-rocks are 

 seen in part near Coldrach, and in the low ground between Glen 



1 See PI. XXXVI, fig. 2 (No. 136). 



