LITHOLOGY OF THE SERIES 



36S 



wackes were formed. It is to be noted that the secondary minerals are 

 in much smaller individuals than those from which they were derived 

 (see figure 2), where hornblende is developing as a secondary product in 

 the metamorphism of these rocks. 



THE HORNBLENDE SCHISTS 



These rocks are regarded as the accomplishment of the processes of 

 rock and mineral alteration acting on the graywackes. A perfectly crys- 

 talline hornblende-schist is the abundant rock in the region west of 

 Moose lake and Sturgeon lake. While hornblende occurs in the freshest 



Figure 2.— Hornblende Grayivacke. 



The original grains of hornblende gray wacke have almost completely disappeared. This figure 

 shows hornblende developing in erystallographic continuity with larger areas of hornblende, also 

 doubtless secondary, developed from original graywacke grains. 1, quartz ; 2, hornblende ; 3, 

 feldspar. Banded portions, new hornblende. 



graywackes of Thomson and Carlton as an interstitial mineral, in the 

 region just named it has developed into the dominant rock constituent, 

 placing even quartz in the background. The parallel position of the 

 grains is usually seen, and the individuals elongated parallel to the 

 axis c. Quartz is present in clear, well defined grains, bearing every in- 

 dication of being secondary. Garnets and magnetite grains are rather 

 numerous. It was observed that toward the surface at every exposure 

 there was a greater proportion of biotite than at a few inches within the 



