Coriindiini-Bcari)ig Rocks of Canada. — Miller. 279 
On weathered surfaces, the rock is grey or at times some- 
what purplish in color. In size of grain, it is medium to coarse. 
Under the microscope, the most abundant constituent is seen 
to be a basic plagioclase. Associated with this are black horn- 
blende, which is green in transmitted light, and, in some cases, 
corundum. This latter mineral, which is almost white or in- 
clining to flesh color, stands up well above the weathered sur- 
face of the rock. Its crystals, on which the planes are not well 
developed, are in the form of thick prisms whose greatest 
length seldom exceeds one and one-half inches. Frequently 
the mineral occurs in the form of lumps rather than crystals. 
Corundum of similar character is described by Holland as 
occurring in a rock "consisting of anorthite (indianite) and 
hornblende chiefly" in India. The specific gravity of a speci- 
men with but little hornblende was found to be 2.824.* 
It may be added that in the Indian and Russian regions in 
which corundum occurs in arothosyte, it is also found in sye- 
nyte and syenyte-pegmatite. Although nepheline syenyte oc- 
curs in the same regions, corundum so far does not appear to 
have been found in this rock outside of Ontario. 
In his description of the corundum-bearing igneous rocks 
of Russia, Morozewicz states that, although rocks of this char- 
acter are. at present, so far as is known, of rare occurence, they 
will be found to occur more widely when search is made for 
them. \ 
The discoveries of these rocks over such a wide tract of 
territory, which have been made in Ontario in old settled dis- 
tricts within the last three years confirm the author's opinion. 
In Ontario, corundum up to the present has been found in 
the following igneous rocks, viz: i. Syenyte (mica, etc.). 2. 
Syenyte-pegmatite. 3. Nepheline syenyte. 4. Anorthosyte. 
The following table shows in which of these the mineral has 
been found in India and Russia according to the descriptions 
given by Holland and Morozewicz respectively: — 
! Ontario 
India 
Russia 
♦Manual Geol. India, Ec. Geo!. 1898. 
tTschermak's Min. Pet Miu. Band X\'III. 
