38 
The plagioclase is an acid labradorite. It is excellently 
twinned according to the albite and carlsbad laws. The 
zonal structure occasionally displayed by the mineral 
shows that there is a certain variation in composition, even 
within the same individual. In many specimens of the 
rock the plagioclase is clearly older than the ferro-mag- 
nesian constituents, since it penetrates or is enclosed in 
the individuals of these latter minerals. In some cases it 
even occurs as perfect crystals entirely embedded in the 
iron ore. 
Nepheline as has been mentioned, is present only in 
relatively subordinate amount. It is allotriomorphic and 
occurs in the interspaces between the feldspar individuals. 
The other minerals present as accessory constituents, 
do not here require further mention. 
The analysis of two specimens of the essexite from 
Mount Royal are given below under No. I and No. II 
page 39. 
The first (No. I) is found in an exposure 100 yards 
(91 m.)) west of the Lookout; it is a variety containing a 
relatively large proportion of the salic constituents, although 
in it as in all the essexite of the mountain, the iron magne- 
sia constituents preponderate very largely. 
The second (No. IT) is an olivine-rich variety of the 
essexite from the Céte des Neiges road, near the reservoir. 
This contains scarcely any salic constituents. In the 
Quantitative System of classification it occupies a hitherto 
unnamed subrang. Its position is as follows:— 
Class IV. Dofemane. 
Order 2. Scotare. 
Section 2. Paoliare. 
Subrang 2. Montrealose. 
At the suggestion of Dr. H. S. Washington this has 
been called montrealose, and the rock montrealite. In 
composition it resembles somewhat closely the essexite 
from Brandberg, Kirchspiel Gran, Norway. 
These may be taken as two typical varieties of essexite 
representing the intrusion as a whole. 
