THE CROWSNEST VOLCANICS. 
27 
Titanite occurs as typically lozenge shape and also tabular 
twinned crystals up to 0*75 mm. long. 
The groundmass is very fine grained, and consists of laths of 
orthoclase, up to 0* 1 mm. long, the larger showing Carlsbad. twins. 
These laths are diversely or fluxionally arranged, often sub- 
parallel to the outlines of the phenocrysts, and make up about 
40 per cent of the groundmass. ALgirite-augite, also about 40 
per cent of the matrix, forms small, irregular grains up to 0 * 03 mm. 
and interstitial to the orthoclase. Analcite forms the major part 
of the remaining 20 per cent of the groundmass, in shapeless 
grains up to 0*03 mm. in diameter. The groundmass contains 
numerous microlites in the shape of colourless rods up to 0 ■ 2 mm. 
long, which are probably apatite. A measurement of the amount 
of analcite in this rock has not been made. It is estimated at 
about 60 per cent. Analyses of this rock are not available, 
Blairmorite f Other Varieties. Besides the two distinct var- 
ieties of blairmorite just described, other specimens occur as 
fragments recognized only in thin section as analcite bearing 
rocks. They are all fine-grained rocks and may be portions 
from the matrix of porphyritic types, as A and B. The mineral 
associations are analcite, orthoclase (or sanidine) segirite- 
augite, melanite, titanite, etc. No hand specimens of these 
rocks have been collected. It is to this variety of analcite 
trachyte that the name blairmorite was applied by Knight. 
The individuality of varieties A and B almost renders them 
worthy of distinctive names, but the rarity of the type, and their 
assured variation, in spite of their unique family resemblance, 
together with the vagueness of Knight’s definition, decided the 
writer to adopt the name blairmorite for these analcite-bearing 
rocks, 
Blairmorite may be redefined as a primary porphyritic 
volcanic rock, characterized by dominant phenocrysts of analcite 
in a matrix composed of analcite, alkali feldspar, and alkali- 
pyroxene, with titanite, melanite, and nephelite, not all of these 
groundmass minerals being necessarily present, and possibly 
others occurring. The rock on account of its ultra-alkaline 
nature will show numerous variations in texture and in pro- 
portions of component minerals, and the above definition has 
not been made more rigid on that account. 
