MINERALOGY OF BLACK LAKE AREA. 
33 
of the form A(331), which appears to be unique, so far as the writers can 
judge from a perusal of the literature to which they have had access. 
The crystals under consideration have the form of square prisms, 
terminated, in some cases at both ends, by various dome-like and other 
forms, and they are obviously monoclinic, with a vertical plane of sym- 
Figure 9 . Diopside, colour- 
less crystal from the Montreal 
chrome pit; idealized inter- 
mediate habit representing the 
average of a number of crys- 
tals, but with the length of the 
prism somewhat exaggerated. 
Figure 10. Diopside, colour- 
less crystal from the Montreal 
chrome pit; tabular habit with 
acute termination, the prism 
and the hemi-pyramid /l (331) 
being the only forms prom- 
inently displayed; this illus- 
trates the average type. 
