372 PROCEEDINGS OF SECTION C. 
A peculiar and probably exceptional form of schist is where 
epidote takes part in the foliated structure ; the foliations being 
of mica, or of epidote and quartz with mica. In one part the slice 
is composed of somewhat larger crystals of epidote and quartz. 
II. IGNEOUS. 
(2) Granitic—A plite. 
4], This rock is peculiar in so far that the felspar is orthoclase, 
microcline, microperthite, and more rarely a plagioclase. These 
crystals are hypidiomorphic and set in a ground mass of quartz in 
interlocking grains. The plagiolase may be oligoclase, but the 
observations as to extinction in the zone P.M. were not conclusive. 
The mica in this rock is in very small amount, in minute flakes, 
or aggregates of flakes, and is both muscovite and biotite. 
43. In another sample the felspars as mostly microcline, more 
rarely orthoclase intergrown with albite veins, thus forming 
microperthite. The plagoclase is in hypidiomorphic crystals and 
obscures as under :— 
P. — + to P. and M. — M. 
4° 40’ — 16° 40’ — 22° 58’ 
With convergent light the trace of the exit of an optic axis is 
visible about the plane T and of a bisectrix on M. These felspars 
appear, therefore, to be albite. A considerable amount of quartz 
and very little mica complete this sample. 
A series of samples illustrates the effects of crushing and of the 
production of a schistose structure in these aplites. 
40. The felspars are of the kind already described, but in this 
sample are broken or somewhat rounded. The rock may be 
described as being composed of a ground mass of comminuted quartz 
and fragments of felspars. In this, which is the “ mortar struc- 
ture ” of some authors, are embedded the felspar crystals, all being 
more or less broken or rounded off. Mica has also been produced 
and forms small foliations in the slice. 
31. In places metamorphism has produced regeneration of 
material, orthoclase crystals being bordered and enlarged by 
micropegmatite. 
26. A further stage is the production of a decidedly schistose 
structure. The rock has been considerably altered so that the 
felspars are much micacised, but it may be described as alternations 
of felspar, probably orthoclase and quartz in irregular foliations. 
Irregular layers of dark-brown iron-magnesia mica also fill in 
cracks and crevices, and are clearly of secondary origin. 
The quartz is in comparatively large fields, but almost always 
has cloudy obscuration. 
This is one of the forms of schistose rock produced by meta- 
morphism of an intrusive plutonic mass. 
