PETROGRAPHIC GEOLOGY AND DESCRIPTIONS. 669 



Granite. Schist.] 



Meg. Schistose. 



Mic. The section consists almost wholly of a fine interlocking background of 

 quartz, or quartz and feldspar, in which are many <i<iinlif<- fibres arranged mainly 

 in one direction, some magnetite with a very little garnet. One section. 



Age. Archean (Keewatin). 



Remark. The foregoing schists stand nearly vertical, forming a bluff at the outlet 

 of the lake which rises about 100 feet, and has been explored for iron. N. H. w. 



No. 1116. GRANITE. 



East shore of White Iron lake at a distance from contact with the schists. 

 Kef. Annual Report, xv, pages 330, 398. 



Meg. Granite. 



Mic. The feldspar (a fresh grain) cut perpendicular to n v in the acute axial 

 angle has extinction on a twinning striation at 88, indicating oligodase. Another 

 section, having , in the acute angle of the optic axes has extinction on n e of 15, 

 which falls between albite and oligoclase-albite. Some grains show the peculiar stria- 

 tion of wirroc/inc. There is also in the rock a series of older, much decayed feld- 

 spars which are frequently zoned. The hornblende of the "rock is almost converted 

 to chlorite. There is comparatively little quarts:. One section. 



Age. Archean granite. N. H. w. 



No. 1117. GRANITE. 



North end of White Iron lake, near junction with the schists. 

 Ref. Annual Report, xv, pages 331, 399. 



Meg. Rather quartzose and fine grained. 



Mic. The rock has much secondary quartz and secondary feldspars, the latter 

 both as zoning about an older feldspar and as separate small grains, which latter are 

 in part of microcline. There is a scant sprinkling of biotite, a little rusted garnet and 

 a few crystals of apatite. One section. 



Age. Archean granite. N. H. w. 



No. 1118. GRANITE AND SCHIST. (Uontw.t.) 



North end of White Iron lake ; junction specimen. 

 Ref. Annual Report, xv, pages 331, 399. 



MC<I. Granite in immediate contact on the schists. 



Mic. In the granite part of the slide is very much quartz in its usual secondary 

 form, with a slight tendency to micropegmatitic intergrowth in the feldspar, of 

 which some of the larger grains are of microcline, in which the peculiar and char- 

 acteristic quadrillage is seen frequently in only a portion of the section, as if it were 

 due to some secondary cause. There is also a little biotite and apparently of garnet, 



