from the Canadian Rocky Mountains. 201 



in the neighbourhood of the watershed of the Rockies. On its left 

 bank the mountains (nepheline-syeuite) form fine craggy peaks 

 and a rocky cirque around its head. Their lower slopes are buried 

 under debris, though here and there furrowed deeply by glens 

 descending from the gaps between the peaks. In one of these, 

 coming into the lower part of Ice River Valley, Mr. Wbymper 

 discovered the sodalite rock in situ at the foot of a little crag, 

 though even here it did not outcrop at the surface, but had to be 

 exposed by digging away the debris, which prevented him from 

 studying its relations with the nepheline-syenite. He also found 

 loose pieces of the sodalite rock all the way to the head of Ice 

 River Valley and in the principal lateral glens; so it must occur 

 among the crags, no doubt in a vein-like fashion, in not a few 

 places. 



He brought away numerous specimens, though many of them 

 were small in size. These are generally coarse-grained, sodalite and 

 felspar being the dominant minerals. They also contain a little of 

 a dull darkish-green mineral, an occasional small flake of brown 

 mica, and a grain of pyrite. Nepheline may be among the felspar, 

 but of that, so far as megascopic examination goes, I am doubtful. 

 The sodalite is a rich blue, deeper in tint than ultramarine, 

 occasionally almost a ' royal blue.' ' The felspar is more or less 

 cream-coloured. The structure of the rook is variable. Sometimes 

 the sodalite is associated with the felspar, much as that mineral 

 is with the quartz in a fairly coarse, almost binary granite. 

 Sometimes the two are less uniformly distributed, so that the rock 

 has a coarsely mottled look, and sometimes sodalite practically pure 

 is streaked or veined by almost pure felspar, or vice versa ; the 

 latter perhaps forming the more regular bands, which may be 

 nearly an inch in breadth. But in a single fragment, a dozen 

 square inches or so in area, the one type of rock may be seen to 

 pass insensibly into the other. The specimens have led me to the 

 conclusion that the rock originally consisted of a very irregular, 

 often streaky mixture (such as may be seen in some ' pegmatite ' 

 veins) of felspar and sodalite or another mineral now represented 

 by it, and that, though it shows some signs of fracture, it is not 

 a brecciated mass of felspar cemented by sodalite. 



Sodalite of a rich blue colour occurs associated with felspar at 

 Dungannon and Faraday, in Hastings Co., Ontario. According to 

 the description of Professors F. D. Adams and B. J. Harrington,- the 

 country rock is a nepheline-syenite, which occasionally is extra- 

 ordinarily coarse, for the crystals of nepheline^' are said to be 

 sometimes over two feet long, and the felspars of corresponding size, 

 the latter, according to Professor Adams, being all plagioclase. The 



1 Mr. Whymper found a few specimens where the mineral was a pale blue. 



- Amer. Journ. Sci., vol. xlviii (1894), pp. 10 and 16 ; see also vol. xlix (1895), 

 p. 465. 



3 Professor Harrington thinks the term elseolite needless, for uo line can be drawn 

 between the specimens with the more oily and the more glassy lustre. So far as 

 I have had the opportunity of judging, the distinction can hardly be maintained. 



