PETROGRAPHIC GEOLOGY AND DESCRIPTIONS. 883 



Jaspilyte and argillyte.] 

 Quartz-porphyry. 



the face of the vertical surface the different pieces can be seen to extend downward 

 for a foot or more in the general mass. The rock must have been at first a banded 

 argillyte." No section. 



Age. Lower Keewatin(?) 



Remark. This structure is illustrated and discussed in volume iv, of the Final 

 lleport, pages 558-562. N. H. w. 



No. 2274. JASPILYTE AND ARGILLYTE. (Interbanded.) 



At the southerly slope of the hill containing conglomeratic argillyte near Moose lake, on the trail to 

 Wood lake. 



Ref. Annual Report, xxiv, page 82. 



Mff/. The weather-banding is very evident. The jaspilitic bands are about 

 a third of an inch in thickness and of a light-grayish color, appearing like flint and 

 nearly black within. The argillitic laminte are about one-sixteenth of an inch in 

 thickness and they weather out more rapidly, producing little grooves that run 

 parallel. No section. 



Age. Upper Keewatin(?) N. H. w. 



No. 2275. QUARTZ-PORPHYRY. 



" Burnt forties," near Soudan, at the corner of sees. 13, 14, 23 and 24, T. 62-15. 

 Ref. Annual Report, xxiv, page 84 ; vol. iv, pages 528-538. 



Meg. Gray, with some feldspar, the probable source of the pebbles of the 

 Stuntz conglomerate. 



Mic. This rock is like numerous others that have been described as quartz- 

 porphyry, or porphyrel. There are numerous old feldspar pieces and crystals nearly 

 perfect, which are uniformly permeated by decay, with development of Muscovite and 

 calcite, and occasionally a distinct bipyramidal quartz. Some of the feldspars are so 

 far decayed that they can with difficulty be distinguished from the matrix. This 

 decay has been interrupted by an opposite process, which has thoroughly permeated 

 the matrix, where it was originally fine grained, and has partly regenerated the 

 feldspars. This regeneration is marked by fresh feldspathic substance which is clear 

 and glassy, seen throughout the matrix and sparsely in the peripheries of the old 

 feldspars. (Figure 4, plate V.) The quartz, where originally fine, has also been 

 recrystallized and is clear and glassy; such quartz also forms a narrow rim about the 

 old original quartzes, which penetrates the matrix and darkens in unison with the 

 crystal to which it is an appendage. It is most marked about the distinctly 

 bipyramidal grains. One section. 



Age. Lower Keewatin(?) 



Remark. This rock differs petrographically in no way from those porphyries 

 and porphyrels which have been described between Moose and Flask lakes, which 

 cut the Upper Keewatin conglomerate of that region. N. H. w. 



