PETROGRAPHIC GEOLOGY AND DESCRIPTIONS. 853 



Conglomerate. Jaspilyte. Graywacke.] 



Mic. In a finely micro-gran ulitic groundmass are altered crystals of feldspar 

 and of hornblende. Much calcite is scattered throughout. 



This pebble appears to be of the same nature as the granitic and porphyritic 

 intrusive rocks at Kekequabic lake, the feldspars being much twinned, somewhat 

 irregularly. See remark under No. 1065. One section. 



Age. Archean (Keewatin). N. H. w. 



No. 2181. CONGLOMERATE. (Greenstone. ) 



Near the same place as No. 2180, but further west. 

 Ref. Annual Report, xxiv, page 57. 



Finely conglomeratic portion of the greenstone lying west from the 

 jaspilyte belt. 



Mic. Largely composed of fragmental feldspars with a copious matrix of 

 debris of the same, also of micro-granulitized pebbles in which are visibly embraced 

 small feldspars porphyritically, in the same manner as in No. 2179, with epidote, 

 calcite and chlorite as usual. One section. 



Age. Archean (Keewatin). N. H. w. 



No. 2182. JASPILYTE. 



Portage from Moose lake to Wood (Wind) lake, near Moose lake ; S. E. % S. W. ^ sec. 20, T. 64-9 W. 

 Ref. Annual Report, xxiv, page 57. 



Meg. The specimens vary from dark-brown jaspilyte to a dark -gray argillyte. 

 Intimately interbanded with the jaspilyte is fine-grained, greenish-yellow material, 

 which is evidently largely epidote. Minute veinlets of quartz cross the specimens 

 and are brought out sharply by weathering. No section. 



Age. Archean (Keewatin). u. s. G. 



No. 2184. GRAYWACKE. (Tuff. ) 



On the trail from Moose lake to Flask lake, sec. 28, T. 64-9 W. The land rises into a ridge or succession 

 of ridges, consisting mainly of conglomerate and graywacke. 

 Ref. Annual Report, xxiv, page 57. 



Meg. The rock is evidently fragmental and conspicuously stratified, spotted 

 with crystals of feldspar. 



Mir. The rock is much decayed. The feldspars are of clastic origin, as parts 

 of a coarse graywacke. Since the matrix is largely, or wholly, not recrystallized by 

 regeneration of the original elements, or by the formation of new elements, it was 

 plainly at first a clastic one. The old feldspars are crowded with little crystals of 

 other minerals, such as mica, calcite and chloritized hornblende. The matrix of these 

 feldspars, which are sometimes perfectly idiomorphic and identical in appearance 

 with those of the graywacke and conglomerate of Zeta lake (Nos. 1062 and 2187), is 



