822 THE GEOLOGY OF MINNESOTA. 



[Quartz-porphyry. Feldspar schist. 



2010. The large quartzes are much broken and the fragments lie adjacent, while a 

 wavy extinction passes over them all. Between these parts is a granular cement 

 appearing to be of quartz or quartz and feldspar, but a little coarser than the cement 

 of the rock at large. This pebble, as seen in the thin section, has a distinct schistosity 

 in the direction in which the fragments of the broken quartzes are separated from 

 each other, and it has more abundant and coarser scales of sericite. One section. 



Aye.. Upper Keewatin (pebble in). 



Remark. These rocks may be compared with others of the Stuntz conglomerate, 

 Nos. 2017 and 2018. These are pebbles that lie in and form parts of that conglom- 

 erate. They have a strong resemblance (especially No. 2010) to rocks Nos. 1789 and 

 2095 (seen at Ely), which are intrusives in the Lower Keewatin. No. 2011 itself 

 appears to be a clastic rock. N. H. w. 



No. 2012. " QUARTZ-PORPHYRY." ( Graywacke. ) 



Prom the extremity of the point nearest the same small island, Vermilion lake. The rock in general is a 

 conglomerate. 



Ref. Annual Report, xxiv, page 12 ; Final Report, vol. iv, pages 530-532. 



Meg. Fine grained, light colored, apparently "quartz-porphyry." 

 Mic. This rock is like No. 2011, except that it contains much more calcite, 

 through greater alteration of the feldspars. It also shows remnants of hornblende in 

 form of actinolite in fibrous, lengthened shreds, and some brightly polarizing scales 

 of sericite. Fine particles, and groups of particles, resembling dark Icncoxene, are 

 visible in ordinary light. One section. 



Age. A stratum of the Stuntz conglomerate. N. H. w. 



No. 2013. QUARTZ-PORPHYRY. (Sheared.) 



On the point, in section 20, a little further west than No. 2012, Vermilion lake. 

 Ref. Annual Report, xxiv, page 12; Final Report, vol. iv, page 531. 



M<'<j. In contrast with No. 2014, the two being pebbles in the conglomerate. 



Mic. Owing to shearing pressure the feldspars and quartzes are considerably 

 broken and separated. There seems to have been formerly a hornblendic element 

 in this rock, but it is lost by the dynamic action to which the conglomerate has been 

 subjected, only traces remaining in the form of elongated chloritic streaks which 

 are isotropic. These are frequently associated with greater amounts of scrir/fi'. 

 Leucoxene appears in formless clusters of particles as in the foregoing. One section. 



Age. Pebble in Upper Keewatin. N. H. AV. 



No. 2014. FELDSPAR SCHIST. 



Same plain; as \o. 2013. 



Ref. Annual Report, xxiv, page 12; Final Report, page 531. 



* 



Meg. This pebble lies in contact with No. 2013. It is finer grained than No. 

 2018 and schistose. 



