so COLEMAN ON THE MICEOSCOPIC 



Muscovite-graniles are uucommou. 



Granite Proper, cousistiug of quartz, ortboclase, plagioclase, biotite aud muscovite, 

 seems rarest of all. 



Our granites vary in grain from rocks with the individual minerals an inch or more 

 in diameter to very fine-grained ones ; and in color from flesh-red, which is common, to 

 light or dark grey, or even light greenish grey, the prevailing felspar usually giving the 

 tone In relative amounts of their ingredients, also, they differ very much, some of the 

 muscovite granites, as observed by Eosenbusch in Europe, being very rich in quartz, 

 while biotite-hornblende-grauites, by increase of these two minerals and diminution of 

 quartz, form a transition toward syenite. In a few pegmatitic specimens mica is almost 

 wanting. 



Felsite. 



Macroscopic. — Quartz porphyries seem to be unrepresented in the drift of this region, 

 unless by a few felsites. These are massive and compact flesh-coloured rocks in which a 

 few quartz blebs and crystals of orthoclase aud i^lagioclase may be recognised with a lens 

 or the naked eye. 



Microscopic. — The bulk of the rock is composed of a micrograuitic magma of quartz 

 and felspar, or else a microfelsitic one, giving a wandering play of light and shade between 

 crossed niçois without distinguishable minerals. The minerals found in these rocks are the 

 same as those of the granites, but generally differing in habitus. No cavities have been 

 observed in the quartz of the magma, though these are common in the porphyritic blebs, 

 and then contain a liquid with a moving bubble and often a cube of salt. In one section 

 a plagioclase crystal has a portion broken out and shifted a little to one side, indicating 

 motion after the formation of this crystal and before the solidification of the magma. No 

 glass or other istropic substance was observed. 



(3.) Massive rocks free from <liiartz or uearly so. 



Syenite. 



This rock is comparatively rare in our drift, and the specimens examined all belong to 

 the biotite-syenites of Rosenbusch. They are coarse or medium grained, reddish or reddish 

 grey in color, and are composed of orthoclase, microcline aud ordinary plagioclase, with 

 much biotite and a little hornblende. Apatite, magnetite and titanite occur as secondary 

 minerals. The descriptions of the constituents of the granites apply fully to those of 

 syenite. 



B. 



SCHISTOSE. 



The acid schistose rocks regularly contain quartz, so that the subdivision " free from 

 quartz," which would correspond to the syenites among the massive rocks, is absent. To 

 this rule a solitary exception has been found in a single specimen of felspar rock in which 

 quartz was wanting. 



