588 THE GEOLOGY OF MINNESOTA. 



[Granulyte. Amphibolyte. Granite. 



considerable kaolinite. The biotite grains have their cleavage in general parallel, 

 and this mineral is more or less altered to chlorite. A little garnet is present. 



Two sections. 



Age. Archean. u. s. G. 



No. 880. GRANULYTE. 



Nodules of irregular forms embraced in the mica schist, No. 879; sec. 14, T. G3-17. 

 Ref. Annual Report, xv, pages 293, 388. 



Meg. Of medium grain, gray, of a syenitic aspect. 



Mlc. Apparently consisted at first of feldspar and quartz, but now, by pressure 

 and probably some shearing, the feldspars are filled with Muscovite, though still 

 showing albite twinning lines, and the quartz is broken into many fragments, 

 showing undulatory extinction. 



One section. 



Age. Archean. N. H. w. 



No. 881. AMPHIBOLYTE. 



From a dike, cut by later dikes, north part of sec. 35, T. 63-16, north part of Vermilion lake, on Pine island. 

 Ref. Annual Report, xv, pages 302, 388. 



Meg. The rock is gray, weathering light-colored; feldspathic and amphibolic, 

 with fine specks of pyrite. There is a marked fibrosity, the minerals being prevail- 

 ingly elongated in one direction. 



Mic. Amphibole makes up a large part of the slide, and the rest is principally 

 a secondary feldspar. Yet there are present accessory amounts of mica and of spit en c, 

 with some zircon and garnet and a little quartz. The last is identifiable only by the 

 observation of a dark cross, since it closely resembles the feldspar. The feldspar 

 has for acute bisectrix, which precludes albite but allows <>H<jwlase. This oligoclase 

 shows no polysynthetic twinning. It is of later date than the amphibole, and 

 usually is in very small grains. The older feldspars are crowded with zoisite. 



Two sections. 



Age. Archean. N . H . w. 



No. 882. GRANITE. (Schistose.) 



From the extremity of the point that projects eastwardly from section 35, into the N. W. J sec. 36, T. 

 63-16 W.; Pine island, Vermilion lake. 



Ref. Annual Report, xv, pages 302, 388. 



Meg. A medium-grained, roughly-schistose, pinkish-green rock composed of 

 red feldspar, chlorite and biotite. 



Mic. The section shows a granitic aggregate of much-altered and clouded 

 feldspar, some quartz, chlorite and biotite altering to chlorite. 



One thick section. 

 Age. Archean. v s G 



