﻿Vol. 66.~\ METAMORPHISM AROUND THE ROSS OF MULL GRANITE. 379 



This series probably represents original shales, sandstones, and 

 mudstones with thin calcareous bands. It is these pelitic gneisses 

 which, followed along their strike up to the margin of the granite, 

 are there found metamorphosed into the sillimanite-andalusite- 

 cordierite-gneiss described in § III of this paper (p. 385). 



Continuing the traverse, about halfway to Bunessan, the pelitic 

 gneisses met with are less quartzose, and they are more finely 

 divided into beds by alternation with the granulitic micaceous 

 quartzites. Farther east, at about a quarter of a mile from Bunessan, 

 near the pier, these quartzite beds become predominant ; but 

 on approaching Bunessan, and thence onwards, the mica-schist is 

 again seen to be the more important member. 



The bands of calc-silicate continue frequent, and are numerous 

 between Bunessan and Loch Assapol. They are often about 1 inch 

 thick and rarely exceed 6 inches, being sometimes lenticular, dis- 

 continuous, or nodular. Frequently the bands are faced on both 

 sides with a thin layer of quartz, which in some cases is connected 

 with veins. They are white rocks, consisting mainly of felspar, 

 quartz, and calcite, spotted with large pink garnets and dark blades 

 of hornblende ; and, when treated with acid, they generally effervesce, 

 especially in the central parts. These bands bear resemblance to 

 the zoisite-amphibolites common in other areas, 1 and possibly re- 

 present impure limestones in the original sediments, which have 

 been acted on by silica during the regional metamorphism. 



Among the pelitic gneisses near Loch Assapol epidiorite bands 

 are met with at frequent intervals. They are tough araphibolite- 

 schists containing some felspar, quartz, mica, iron oxide, and, in 

 most cases, abundant large garnets which stand out on the 

 weathered surfaces. These old intrusions are rarely seen to trans- 

 gress the bedding even to a slight extent, and evidently were sills. 



It is in this tract that tourmaline, kyanite, and staurolite are 

 found along the outcrop of two particular belts of rock, which are 

 separated from the granite by the 2 miles of ordinary unaltered 

 Moine rocks which have now been briefly described. An account 

 of them is given in § IV of this paper (p. 391). 



After a later quartz-porphyry sill has been passed over, and 

 proceeding eastwards from Loch Assapol, the coarse quartzose type 

 of pelitic gneiss is seen to become more conspicuous ; ultimately 

 white quartzite beds are again crossed, and the south-eastern tract 

 of psammitic Moine rocks is reached. 



Pegmatites. — Throughout the pelitic series which has just been 

 described, veins of quartz and knots and patches of ' pegmatite ' 

 abound. These participate in the folding of the schists, and near 

 the margin they are cut by the apophyses of the granite. They are 

 further discussed in § IV (p. 391). 



1 Summary of Progress of Geol. Surv. for 1897, p. 41 : ibid. 1900, p. 10; 

 and ibid. 1902, p. 85 : also ' Geology of Lower Strathspey ' (Expl. of Sheet 85) 

 Mem. Geol. Surv. 1902, p. 47. 



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