PETROGRAPHIC GEOLOGY AND DESCRIPTIONS. 613 



Granite. Iron Ore.] 



No. 958A. GRANITE. 



Same place as No. 958. 



Ref. Annual Report, xv, pages 333, 391. 



Meg. A fine-grained, dark-gray, granitic rock. This sample represents the 

 dark masses included in No. 958, and is spoken of in the field notes as a mica schist. 

 The hand specimen is too small to show the schistose character of the rock. 



Mic. A granitic aggregate of feldspar, quartz, hornblende and biotite. Some 

 micropegmatyte is present. The rock may be a quartz dioryte rather than a granite; 

 the feldspar was not determined, but considerable of it is plagioclase. 



One section. 



Age. Archean. u. s. G. 



No. 958B. GRANITE. (Vein.) 



Same place as No. 958. 



Ref. Annual Report, xv, pages 333, 391. 



Meg. From a small vein or dike in No. 958A. The component minerals are 

 quartz and feldspar. 

 No section. 

 Age. Archean. u. s. G. 



No. 959. GRANITE. (Bwtitic. ) 



Sec. 23, T. 61-12 W.; north shore of Birch lake. 

 Ref. Annual Report, xv, pages 334, a36, 391. 



Meg. A fine-grained, gray granite. 



Mic. A granite whose essential components are quartz, feldspar and biotite. 

 Magnetite and chlorite are also common. 

 One section. 

 Age. Archean. u. s. G. 



No. 960. IRON ORE (with olivine, etc.}. 



S. E. J4 S. W. % sec. 24, T. 61-12 W.; near north shore of Birch lake. 



Ref. Annual Report, xv, pages 335, 339, 391; Annual Report, xvii, page 195. 



Meg. A heavy, crystalline rock, composed largely of magnetite and with 

 another mineral which is in large plates. Compare Nos. 976, 1138. 



Mic. The rock is one of the " olivinitic iron ores," which are found in a 

 number of places along the north side of the gabbro. There are several sections 

 of this number, showing varying conditions. The essential minerals present are 

 magnetite, pyroxene, olivine, quartz and amphibole (perhaps grunerite). The pyroxene 

 is both monoclinic (diallage) and orthorhombic ( enstatite or lujpersthene) and the two 

 are sometimes intergrown. Five sections. 



Age. Keewatin or Animikie. u. s. G. 



