THE CROWSNEST VOLCANICS. 
19 
The groundmass is made up of about 50 per cent lath 
shaped untwinned feldspar, probably orthoclase, the remainder 
being a formless, isotropic, green substance, perhaps aegirite- 
augite glass. This latite is an alkaline variety, and clearly re- 
lated to the rocks with which it is found. 
Some small fragments in the thin section cut from field 
specimen 7, contained small phenocry sts of plagioclase with sharp 
albite twinning, which seems to be oligoclase, about Ab 70 An 3 o- 
The groundmass consists of rods of feldspar up to 0-07 mm. 
long, and a greenish mineral, probably aegirite-augite. Single 
crystals of oligoclase and andesine occasionally occur in the tuffs, 
and Knight remarks:— 1 
“From this it may be inferred that parts of the magma 
from which these clastic rocks were derived had the composition 
of andesite. The type is quite insignificant, the series as a 
whole being characteristically trachytic.” 
The assumption that parts of this magma were as basic as 
andesite does not seem quite justified by the evidence in hand. 
Tingaaite. 
Although this variety of rock was not noted by the writer, 
the description given by Knight 2 is added for completeness: — 
“It is a holocrystalline porphyritic rock with phenocrysts 
of orthoclase (over an inch in diameter) and augite set in a 
groundmass of orthoclase laths, nephelite, and many aegirite 
prisms and needles.” 
Analcite-bearing Rocks. 
At least three distinct varieties of these peculiar rocks 
have been recognized, and others doubtless remain to be dis- 
covered. Knigfyt (loc. cit. p. 275) predicted the finding of 
volcanic rocks of this type, containing analcite phenocrysts, 
and his suggested locality name, blairmorite , has been adopted 
for the group. 
Blairmorite ; Variety A. This extraordinary rock (field 
specimen 31) was found as a rounded water worn fragment 
about two feet in diameter, one of a few similar but smaller 
1 Knight, C. W. Can. Rec. Sci., vol. 9, No. 5, 1905, p. 275. 
*Idem. p. 274. 
