190 
outer boundary of the host this property is strongly develop- 
ed. АП contain liquid inclusions with moving bubbles, but I 
think the 1ndividuals nearer the centre of the felspar contain 
fewer than those cioser to tko periphery or than the inter- 
stitial quartz. The latter occurs in relatively somewhat larger 
grains. It is perfectly angular, and shows the effects of strain 
in its shadowy extinction, incipient, and even advanced frac- 
ture. Much of it shows pegmatitic intergrowth with the 
albite. 
Magnetite, as already stated, is remarkably abundant for 
so acid а rock. It occurs in idiomorphic subidiomorphic and 
irregular grains scattered through both the other minerals. 
It has not undergone much decomposition, but has neverthe- 
less given rise to some staining of the rock with red and yel- 
low oxides of iron. An interesting feature is that in the 
majority of instances the grains of magnetite are surrounded 
by a partial or complete halo of muscovite, giving bright 
polarisation tints. 
Muscovite is very scarce in the rock. No large sections at 
all occur, but it all assumes the form of fine flakes around 
the magnetite grains, or grouped in aggregates with the 
general characteristics of what has been called in the other 
rocks described secondary muscovite. That some, perhaps 
all, of it may really be primary is rendered possible by the 
fact that some of the magnetite grains provided with halos 
are completely surrounded by quartz, and it is difficult to 
see how muscovite could be formed secondarily in such a 
position. 
GNEISSIC GRANITE, OUTCROP BEHIND OLARY. 
Macroscopic Characters.—The rock is yellowish-pink in 
colour, holocrystalline, but somewhat fine in grain. It is 
markedly foliated in band specimen. Under the lens it 18 
found to consist of quartz, felspar, and chlorite. 
Quartz is abundant in smal!, rounded grains, and is clear 
to milky. The felspar sections are mostly small, but here 
and there a comparatively large section is met with in the 
form of an "eye," though typical “augen” structure is not 
well developed. The mineral is flesh-coloured, and shows 
Carlsbad and albite twinning where the sections are large 
enough to show structares distinctly. Only a small amount 
of muscovite is developed, and this is in small pieces. Biotite 
is much more plentiful, and occurs in streaks, giving the 
rock the foliated appearance. The piece of rock under ex. 
amination contains several foreign fragments. One of these 
is a small piece of sericite schist about 25 mm. x 10 mm. x 
3 mm. All the others are fragments of vein quartz. 
on E 
