Some Canadian Rocks containing Scapolite. 198 
while in sections parallel to the clinopinnacoid, the extinc- 
tion is seen to be about 39° or 40° against C. Most of the 
pyroxene has a peculiar, fibrous or mottled appearance, 
due to what is apparently its partial alteration into a light 
green pleochroic hornblende. This hornblende is darker 
in colour and generally has a shred-like character at its 
contact with the pyroxene, the two minerals, however, 
often having a sharp line of contact, which in this case is 
usually a cleavage trace. The various patches, streaks or 
shreds of hornblende scattered through an individual of 
pyroxene generally have a common orientation, presenting 
elongated forms in prismatic sections of the pyroxene, but 
on basal sections generally appearing as irregular spots, 
the hornblende strings being inlaid parallel to the C axis of 
the pyroxene, and sometimes also elongated parallel to 
«2 P o, both minerals having the B axis in common. 
In addition to the hornblende associated with the pyrox- 
ene, the rock contains other hornblende which shows no 
evidence of derivation from pyroxene. This is of a deep 
green colour, has the usual perfect cleavages, and occurs 
scattered througb the rock in irregular shaped masses, 
which however occasionally have well defined prismatic 
contours. The pleochroism is strongly marked @—=dark 
bluish-green ; M=dark green; A=light yellowish or brown- 
ish-green. 
The scapolite is abundant, and occurs in large, colour- 
less grains. In basal sections a very distinct uniaxial 
figure was repeatedly obtained, and by means cf the 
quarter-undulation plate its negative character was clearly 
established. The quadratic cleavage parallel to o Po is 
distinct. The polarization colours are either brilliant or 
are of a pale bluish-gray tint like those of the feldspars. 
The brilliantly polarizing scapolite occurs side by side with 
that which shows the soft gray tints, so that the difference 
does not seem to be due to a varying thickness of the sec- 
tion. In two instances, traces of polysynthetic lamelle 
were observed, in which the extinction, though much less 
distinct than in plagioclase, resembled it otherwise very 
