PETROGRAPHIC GEOLOGY AND DESCRIPTIONS. 847 



Greenwaeke. Green schiat. Serpentine.] 



No. 2146. GREENWACKE. 



Straggling (dike?) cutting No. 2145. 

 Ref. Annual Report, xxiv, page 49. 



Meg. Fine-grained, weathering lighter, with schistosity parallel with that of 

 the enclosing rock. 



Mic. This appears now like a schist. Old feldspars, secondary feldspars, calcite, 

 leucu.cene, and some mica compose this rock. One section. 



Age. Archean (Keewatin). 



Remark. Neither the field relations nor the petrographic characters are 

 sufficient, nor both together, to determine whether this rock exists as a dike or a 

 part of the elastics. The occasional crowding which it manifests upon the other 



beds, indicating an intrusive nature, may be due to crumpling and overthrust, while 

 the microscopic characters rather favor a clastic origin. N. H. w. 



No. 2148. GREEN SCHIST. 



A little further south but still on the S. W. ^ N. E. J^ sec. 36, T. 64-11. Saturday lake ; a second low bluff. 

 Kef. Annual Report, xxiv, page 49. 



Meg. Rock is more uniform, but having scattered siliceous and calcareous spots, 

 somewhat resembling amygdaloid, the silica areas sometimes being from two inches 

 to two or three feet in diameter. The weathering of the calcite gives a decided 

 aspect of porosity. 



Mic. It is evident that these areas are of secondary origin, due to the replace- 

 ment of some of the minerals by calcite and quartz, the latter being micro-granulitic 

 and probably secondary after feldspar, while the calcite is the result of the same 

 replacement, but accumulated as pseudamygdules. Calcite, moreover, is distributed 

 widely through the rock in general. One section. 



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



No. 2148A. SILICEOUS PART OF No. 2148. 



Same place as No. 2148. 



Ref. Annual Report, xxiv, page 50. 



Meg. Of irregular shape, evidently not wholly of quartz. 



Mic. The quartz is of pneumatolitic origin and micro-granulitic structure, but 

 the grains vary considerably in size. Nine-tenths or more are of such quartz, the 

 rest being calcite and epidote. One section. 



Age. Keewatin. N. H. w. 



2158. SERPENTINE. ( Imperfect. ) 



Southwest corner of sec. 16, T. 64-10, Bassimenan lake. 

 Ref. Annual Report, xxiv, page 51. 



* 



Meg. Apparently originally peridotyte. 



