14 
MUSEUM BULLETIN NO. 4. 
PETROGRAPHY. 
PRELIMINARY STATEMENT. 
The following description of the petrography of the Crows- 
nest volcanics comprises: a summary of the results of the work 
done by C. W. Knight in describing these rocks; descriptions 
of the primary rock types found in the breccias by the present 
writer, with one analysis; descriptions of the present types of 
pyroclastic rocks noted ; a discussion, summary, and conclusions 
in regard to the petrology of the volcanics. 
SUMMARY OF KNIGHT’S RESULTS. 
The specimens studied by Mr. Knight were collected in 
1902 by Mr. W. W. Leach, and belong to the collection of the 
Geological Survey of Canada. He notes the following rock 
types: 1 augite trachyte, tinguaite, andesite, and analcite trachyte. 
The last type is represented by an analcite-orthoclase tuff, 
which he names blairmorite-tuff, after the town of Blairmore, 
Alberta, near where some outcrops of the rocks occur. He 
suggests the name blairmorite for a rock, the probable finding 
of which he predicts, and which will contain icositetrahedral 
phenocrysts of analcite. He also describes a rock fragment 
of this type consisting of (foe. cit. p. 275) “ phenocrysts 
of orthoclase and analcite less than 1 mm. in diameter set in 
a groundmass of feldspar laths (a few of which have the 
twinning lamellae of the plagioclases) and a few smaller anal- 
cites. Some titanite is also present ”, 
The following minerals were noted by Knight in the speci- 
mens loc. cit. p. 207 : — 
“Orthoclase, sanidine, analcite, augite, segerite-augite, 
aegirite, acmite, diopside, titanite, microcline, anorthoclase, 
andesine, nephelite, hornblende, apatite, biotite, garnet, mag- 
netite, and various secondary minerals, such as chlorite, limonite, 
calcite, etc. Sodalite is probably present in small quantities, 
1 Knight, C. W. Can. Rec. Sci., Montreal, vol. 9, 1905, pp. 265-278. 
