THE CROWSNEST VOLCANICS. 
21 
The second generation of analcites are much smaller, and 
rarely exceed 0*3 mm. in diameter. They are yellowish or pink- 
ish, and idiomorphic as a rule, in eight sided or rounded sec- 
tions, but the edges are not always sharp. 
iEgirite-augite occurs sparingly as tabular idiomorphic 
individuals up to 0*75 mm. long. Some sections exhibit 
zonal banding and segirite rims are occasionally found. The 
segirite-augite is usually quite fresh. 
Nephelite is found in rectangular individuals up to 0*5 
mm. long, and is also quite unaltered. 
A fresh, clear feldspar with a very small axial angle occurs 
very rarely, and is thought to be sanidine. Carlsbad twins, 
up to 0 • 5 mm. long, have been seen. 
Melanite is rare in occurrence, and is of the usual type 
seen so frequently in these rocks. 
There were three rather distinct periods of crystallization 
during the solidification of this blairmorite. The large analcites 
grew first to their unusual size on account of the great excess 
of this material in the magma, and are of mtratellurie origin. 
The second generation of phenocrysts then formed, probably 
rather rapidly and more or less simultaneously, although relative 
perfection of outline hints that segirite-augite, melanite, 
sanidine, analcite, and nephelite may have been the order. 
The third crystallization stage was the forming of the matrix, 
which is only incipiently crystalline. 
This blairmorite is remarkable for the large percentage of 
primary analcite it contains. The size of the larger pheno- 
crysts allowed a measurement of the relative amounts of anal- 
cite of the first generation and the groundmass to be made 
without difficulty. It was found by determinations on several 
specimens that the surface areas of the larger phenocrysts and 
matrix were almost exactly equal, so it was concluded that the 
volume relations were in the same proportion. The matrix, 
on measurement by the Rosiwal method, was found to contain 
50 per cent of recognizable analcite by volume 1 . This gave 
The precision of the determination of the proportion of the larger pheno- 
crysts is about 1 per cent ; that of the analcite in the matrix probably between 
1 and 2 per cent. 
