45 
Mount Royal, between Céte de la Visitation and Maison- 
neuve. It is a fine-grained, greenish-grey rock and is 
often very fresh. It is quarried for road metal and con- 
crete at several points in the district mentioned above. 
It very frequently contains nosean and under the micro- 
scope is also seen to hold small amounts of rinkite, lavenite 
and other rare minerals, owing to whose presence it is 
highly radio-active. An analysis of the rock from the 
quarry at Papineau avenue is given under III, page 46. 
Nepheline Aplite——Small dykes of this rock, usually 
quite narrow, are seen at the Corporation quarry and else- 
where in the district. The rock is light in colour, and 
often nearly white, and is composed of nepheline and 
orthoclase. It is frequently rather coarse in grain, thus 
approaching a nepheline syenite pegmatite in character. 
Analcite dykes.—These dykes are bluish-grey in 
colour and have a peculiar pitchy lustre. They contain a 
large amount of an isotropic base, in which there 
are embedded a few phenocrysts which are almost exclu- 
sively of an alkali feldspar and nepheline. The isotropic 
base has the refractive index and composition of analcite. 
The isotropic base of monchiquites has been shown by 
Pirsson, in certain cases at least, to be analcite and not glass. 
It is believed that the base in these rocks is also analcite, 
although it has not been possible as yet to obtain any 
positive proof that such is the case. One of the largest 
and most typical of these dykes is to be seen at the Mile 
End quarries. An analysis of it is given under VI, p. 46. 
The rock is vey fresh and free from decomposition products. 
It ranks as laugenose in the Quantitative Classification. 
Monchiquite.—These rocks resemble the camptonites 
in being very dark or black in colour and fine in grain, 
but differ from them in that they possess a groundmass 
or basis of some isotropic material. The two rocks cannot 
as a general rule, be distinguished in the field. Although 
not so abundant as the camptonites in this region, they 
are very common and form one of the most characteristic 
classes of dyke rocks connected with the intrusions of 
Mount Royal. They occur in all parts of the area, but are 
usually considerably altered. Analyses of two of these 
dykes are given (Nos. VII and VIII) on page 46. The 
first (No. VII) is a hornblende monchiquite from a dyke 
18 inches (46 cm.) wide cutting the Trenton limestone at 
