306 TJie American Geologist. November, i89» 
ly by the parti -colored polarization which sometimes repre- 
sents exactly the original crystal form of the idiouiorphic 
augite, surrounded by fringes of external growth beyond the 
augite limits. When the augite grains were fragmentary, or 
were corroded before being enclosed in this rock, the horn- 
blendic growths have exactly filled them out, the dark color 
of the polarization (or even the color seen in ordinary light) 
showing distinctly the original augite outlines. Besides the 
conspicuous hornblendes sometimes this schist contains traces 
of feldspars, but usually feldspar is not evident except when 
the whole rock becomes coarser. When feldspar is seen dis- 
tinctly in the schist, the crystals often appear to have been 
altered into a micro-granulitic mass of secondary grains which 
appear to be of quartz and feldspar. Sometimes pellet-like 
spots appear, under the microscope, which are occupied by 
such granulation. By their assuming distinctly lighter and 
darker aspects four times in one revolution, there appears to 
be a remnant of the original feldspar grain with its orientation 
still intact. The "ground mass," so' to speak, surrounding 
these altered crystals, is composed largely of finer condition 
of the same elements, but usually it embraces also a notable 
amount of quartz, which is in the form either of free grains 
of angular clastic shapes or of fine and intimately interlocked 
chemical deposition. With the fine-grained quartz is appar- 
ently also equally fine feldspar. 
This green schist is sometimes composed almost wholly of 
actinolite spicules. At other, places it passes into a greenish 
graywacke. It is distinctly a fragmental rock, and shows 
a coarse, even pebbly structure, the pebbles being usually of 
rock like itself, but finer-grained. It is considered to be large- 
ly of the nature of an old volcanic tuf¥, grading, as it does, into 
the greenstones of the Keewatin. 
In the first place it should be noted that there is a strik- 
ing mineralogical afBnity between the schist-conglomerate and 
the crystalline rock, in that they both contain augite, and that 
this augite is of the nature of aegyrine; also that the feldspars 
of the schist-conglomerate, having very striking and unusual 
characters, are duplicated in the granites — i. e., the original 
feldspars are remarkably twinned and zoned. This statement 
as to the augite is not demonstrated, but rests on the concur- 
