92 
Collectively, these gneisses present evidence of being 
a series of altered sediments, though if each one were 
considered separately, it would be difficult to arrive at 
any definite conclusion regarding its origin. 
An altered limestone from the tunnel on the south 
face of the hill, contains in addition to calcite a green, 
slightly pleochroic pyroxene, some scapolite and large 
rounded grains of pink titanite. 
Gneiss from the north-east part of the map area has 
pink titanite as its most important coloured constituent, 
though biotite and hornblende are also present. Orthoclase 
and microcline are the two most important constituents; 
quartz, plagioclase, scapolite and calcite are less important. 
A very small amount of the quartz is intergrown micro- 
graphically with the feldspar. The rock possesses a well- 
developed gneissic structure due to a parallel arrangement 
of the mica flakes, to the ‘“‘mortel-structure,’’ more especial- 
ly of the feldspars and to the strain-shadows in the quartz. 
The scapolite shows no evidence of strain-shadows, or 
granulation, which would indicate that this mineral had 
been formed subsequently to the application of pressure, 
or as a result of its application. The micrographic inter- 
growth of quartz and feldspar indicates an igneous origin 
for this rock. 
Hypersthene-granite (charnockite), typical of the south- 
ern part of the hill, is characterized by considerable amounts 
of strongly pleochroic hypersthene and pink garnet, and 
a large amount of quartz. In fact, this latter mineral is the 
only one that catches the eye in weathered hand-specimens. 
Plagioclase is more important than orthoclase, but both are 
much subordinate to quartz. Brown biotite and zircon 
are the only other constituents. The quartz is granulated 
and both quartz and feldspars show strain effects. 
Garnetiferous gneiss. Associated with the hyper- 
sthene-granite are quartz and pegmatite veins, and bands of 
garnet-gneiss, which may be related to the hypersthene- 
granite in the same manner as similar rock-types are 
related to the charnockites of southern India. Pink 
garnet, the most important constituent of this gneiss is 
very conspicuous in the hand-specimen. It often contains 
biotite or feldspar inclusions. Brown biotite, an important 
constituent, has crystallized after the garnet. Orthoclase 
is much the most important feldspar, though microcline, 
plagioclase and microperthite are also present. The 
