848 THE GEOLOGY OP MINNESOTA. 



[Amphibolyte. Quartz-feldspar schist. 

 Quartz schist. 



Mic. This rock is largely serpentinized, but there are remnants of all the 

 original minerals. The structure is wholly destroyed, apparently by decay and by 

 crushing. One section. 



Age. Archean (Keewatin). 



Remark. This rock has been used by the aborigines for making pipes. 



N. H. w. 

 No. 2159. AMPHIBOLYTE. (Epulotic.) 



Sec. 16, T. 64-10, Bassimenan lake. At the dull, high point just west of the mouth of the river which here 

 enters the lake. 



Ref. Annual Report, xxiv, page 52. 



Meg. Schistose, hornbleudic, with patches that weather lighter. 



Mic. The rock is largely of hornblende and epidote, with a little xjihcnc. What 

 little feldspar there was in this rock formerly has been replaced by an irregular 

 interlocking group of secondary feldspars. One section. 



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



No. 2161. QUARTZ-FELDSPAR SCHIST. 



Midway on the portage between Oak Point lake and Little Sucker lake, T. 04-10, lying next south of the 

 area of granite. 



Ref. Annual Report, xxiv, page 52. 



Meg. Gray, fine-grained, siliceous, pyritiferous, schistose. 



Mic. Evidently a sheared fragmental rock, consisting of fine angular quartz 

 grains, some old feldspars, mica, pyt'ite, epidote. It is evident that a great many old 

 feldspars have been altered into the micro-granulitic mosaic (quartz and feldspar) 

 which is also the product sometimes of recrystallization from a schist of clastic 

 origin to a new rock, approaching granite in proportion as this replacement is coarser 

 and more 1 and more prevalent. One section. 



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



No. 2162. QUARTZ SCHIST. ( Jaspilitic. J 



Little Sucker lake, south shore, near the portage going to Pine lake ; sec. 27, T. 64-10. 

 Ref. Annual Report, xxiv, page 52. 



Meg. Very siliceous, weathering nearly as white as a granite, fine grained, 

 gray-green within, fibro-schistose, but not visibly laminated, rising in bold glaciated 

 bosses on the weathered surface pitted from decay of some of the elements of the rock. 



Mic. The rock consists essentially of fine interlocking quartz, but with a 

 liberal cement of calcite, muscovite and of chlorite or chloritized hornblende. There 

 are a few tourmaline crystals and frequent spiculesof rutile, and apparently of actino- 

 lite. The pitted aspect of the weathered surface is due to the weathering out of the 

 chloritic or calcitic areas. One section. 



Age. Archean (Keewatin). 



