CHARACTER OF ROCKS NEAR CONTACT. 323 



The separate grains of epidote in each nest have for the most part all a common 

 orientation and extinguish together. None present crystallographic boundaries 



nor distinct cleavages." 



Microscopic Examination of the Gneiss. — A specimen of the gneiss ob- 

 tained from the contact on the line between lots 4 and 5, concession III, 

 showed its contact with the Huronian schist. Of this Dr Lawson says : 



"A pinkish to yellowish gray medium-textured biotite granitoid gneiss, with a 

 portion of very fine-textured greenish gray schist partly adhering to and partly 

 enclosed in the granite on one side of the specimen. The thin section examined 

 is across the contact of the granite gneiss and the schist. In the section the two 

 rocks are very distinct, and the contact, while fairly sharp, shows portions of the 

 schists included within the granite. The granite is a granular aggregate of ortho- 

 clase, microcline, plagioclase, quartz, biotite and muscovite. * * In the struc- 



ture of the rock there are some slight evidences of pressure seen in the occasional 

 dislocation of a crystal of plagioclase, but there is neither shearing nor cataclastic 

 structure. The schist in contact with this granite is profoundly sheared, and it 

 only requires an inspection of the slide to see that the shearing was effected before 

 the magma from which the granite has crystallized was brought in contact with 

 the schist. The schist is composed essentially of quartz and muscovite, and these 

 minerals are arranged in parallel thinly lenticular areas which wedge into one 

 another. The optical tension of the quartz lenses is very constant. The cataclastic 

 structure of the quartz is pronounced. The general aspect of the schist is that of 

 a streaky rhyolite." 



( 'haracter of the Rocks near the Liar if Contact. — Near the line of junc- 

 tion the silicious slates and quartzites become highly schistose and show 

 signs of having been subjected to great pressure. Angular pieces of the 

 schistose rocks are included in the gneiss, especially near the curve in 

 the line of junction, while intrusions of gneiss were seen at several places 

 penetrating the stratified rocks. In one instance a lenticular mass of 

 distinctly foliated micaceous gneiss was seen intruded through the schists 

 parallel to their bedding at a distance id' three hundred yards from the 

 line of contact. Besides these gneissic intrusions there are irregularly 

 shaped fissures running transversely to the strike of the schists and filled 

 with coarsely crystalline feldspar and quartz. In the larger portions of 

 these veins the feldspar and quartz are present in about equal propor- 

 tion, but where they begin to thin out quartz seems to be the main and 

 in some cases the only constituent. These pegmatitic apophyses are 

 evidently portions of the adjacent gneiss which have been injected 

 through the schists and crystallized in the presence of heated vapors. 

 A large pegmatite vein of this sort was noticed on the line between 

 Broder and Dell extending across the strike of the schists for a distance 

 of half a mile from their contact with the gneiss. 



