644 THE GEOLOGY OF MINNESOTA. 



[Granite. Graywacke. 



light yellow (in the section examined), while the older grain is of the dark tint of 

 the first order. The extinction occurs in a shadowy manner, and in fan-shaped 

 patches, showing different orientations, somewhat in the manner of broad spherulitic 

 groups having always positive elongation, but without any other visible spherulitic 

 structure, the later feldspar (b in figure 38) having the same extinction as the earlier. 

 The name of this poikilitic mineral was not determined, but is supposed to be 

 orthoclase in two conditions, viz.: ordinary and deformed orthoclase, cut in the zone 

 (001) (010), the pseudo-spherulitic or lamellar structure being parallel to the 

 axis b, constituting a coarse microperthite. Compare No. 1034. 



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



No. 1052. GRANITE. 



W. % sec. 3, T. 64-7. Kekequabic lake, from near the contact with No. 1051. 

 Ref. Annual Report, xv, pages 364, 395. 



Mey. Red rock, same as No. 1046. 



Mic. Though much finer grained, this is a rock like. Nos. 1044-1046. The 

 hornblende is in small, irregular areas, not in spicules. There is the same distinction 

 between the old and the new feldspars, the latter being clear and glassy, and the 

 former cloudy. The new growths form the cementing band, as they constitute 

 interlocking arms and hooks, sometimes originating from the older grains and some- 

 times being apparently entirely free from them. The rock has the appearance of 

 having quartz in the new material, but owing to the fineness of the grain none can 

 be detected in convergent light. The feldspars are twinned on the albite and Carls- 

 band plans and apparently on the microcline, and the larger ones are occasionally 

 zoned. One section. 



Age. Archean (igneous). 



Remark. Were it not that this rock is so intimately connected in the field 

 relations with rocks Nos. 1044-1046, and those through No. 1051 with rocks Nos. 

 1047-1050, it might be difficult to affirm its original fragmental character. But 

 the microscopic characters entirely agree with the field relations and indicate that 

 both groups are recrystallized debris. N. H. \v. 



No. 1053. GRAYWACKE AND SLATE. 



N. W. % sec. 3, T. 64-7 W. West side of Kekequabic lake. 

 Ref. Annual Report, xv, pages 365, 395. 



Meg. There are two small hand samples of this number. One is a rather fine- 

 grained, gray, gritty rock. The other is a fine-grained, dark argillyte. Both hold 

 pyrite. No section. 



Age. Archean (Keewatin). u. s. G. 



