042 Messrs. Clough, Crampton, and Flett— a 
schists. In the Loch Chaoruinn district the rocks are further arranged 
in the form of a syncline, traceable by means of one of the andalusite | 
bands mentioned above. This syncline is truncated on the one hand | 
by the granite margin and on the other by the schistose rocks. The | 
pelitic mass in the areas just referred to isin the condition of hornfels, 
except along a narrow belt in contact with the granite, and at its 
outer margin next the psammitic schists, in both of which positions 
it has generally undergone considerable shearing. ‘The pelitic outcrop, 
which originally must have been a single mass of shale or sandy shale, 
is now at some points an unsheared hornfels, while at others it has 
been converted into a garnetiferous mica schist, with folds and 
foliation striking at right angles to the bedding in the hornfels. 
As we proceed outward from their centres the masses of hornfels 
in other areas also can usually be traced passing into mica schist, - 
whether we move towards the granite or away from it. There are 
many intermediate stages between typical hornfels and typical mica 
schist, one of the best marked being a fine greyish rock full of small 
micas, white and black. This may be called the stippled schist, and 
often forms a belt next to the granite. It has more mica than the 
hornfels, especially muscovite, which has developed at the expense 
of felspar. The garnets of the hornfels persist, but the sillimanite 
and andalusite disappear. The latter passes first into kyanite, and 
pseudomorphs of kyanite after chiastolite, retaining the original 
outlines and structure, though consisting only of aggregates of small 
divergent prisms, may often be seen. These we take to be illustrations 
of the efficiency of pressure in substituting that form of the silicate 
of alumina which has the highest specific gravity and least molecular 
volume. Later the andalusite crystals are greatly bent and puckered 
and converted into white mica, the large prisms being then drawn out 
into pale films that lie along the cleavage. 
The stippled schists are fissile, as their micas have a parallel 
orientation that is lacking in the hornfels. This is a new structure, 
namely, foliation. The direction of orientation often crosses the 
bedding, and as the foliation develops the sedimentary banding gets 
less evident, though still persisting. The rocks are being sheared 
and interstitial movement is taking place; the dragging out of the 
andalusite proves this and also the deformation of the quartz pebbles. 
In the other schists, which are more coarsely crystallized than the 
stippled schists, the mica plates get longer and larger; felspar 
vanishes almost completely, though sometimes a little albite makes 
its appearance. The ultimate product is a mica schist with each 
plate of mica a hundred to a thousand times larger than those of the 
hornfels. We note the operation of three processes closely connected— 
(1) interstitial movement, (2) recrystallization with orientation of the 
micas perpendicular to the directions of stress or along the planes of 
movement, (3) continued growth in size of the characteristic minerals 
of the schist. Here again chemical analyses have proved that the 
coarse mica schist was originally the same rock as the fine blue 
splintery hornfels. It is probable, however, that the extreme outer 
margin of the pelitic band near Kildermorie never was in the condition 
of hornfels, but was converted directly into mica schist. 
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i 
