632 THE GEOLOGY OP MINNESOTA. 



[Greenstone. 



rocks, but it is difficult to say whether it is hornblendic or chloritic. It composes 

 the most of the matrix of the feldspars, but is not entirely wanting in them. Quartz 

 is wanting or scarce. One section. 



Aye. Archean (Lower Keewatin). N. H. w. 



No. 1019. GREENSTONE. 



Same place; same rock surface as the last. 

 Ref. Annual Report, xv, pages 327, 394. 



Meg. Similar schist, schistose. 



Mir. Rock is very like the last, a little coarser grained, with less frequent 

 feldspar microliths, but with a large area in which either a rock fragment was 

 enclosed of a different sort, or a different alteration has progressed. In this area are 

 numerous angular quartzes. The leucoxene is lighter colored than in the last. One 

 section. 



Age. Archean (Lower Keewatin). N. H. w. 



No. 1020. GREENSTONE. 



Same place; same rock surface as the last. 

 Ref. Annual Report, xv, pages 327, 394. 



Meg. Coarsely schistose, but similar to the last. 



Mic. A little coarser grained, but essentially the same as the last. There is, 

 however, a stronger suggestion of an original ophitic structure in the disposition of 

 the feldspars, and especially as in two or three instances one is seen to cross another 

 at a considerable angle without change of orientation by either. Brown leucoxene is 

 common. One section. 



Age. Archean (Lower Keewatin). N. H. w. 



No. 1021. GREENSTONE. (Oranuhn:) 



Same place as the last; same exposed surface. 

 Ref. Annual Report, xv, pages 327, 394. 



Meg. Similar to the last, but evidently changed from an igneous debris. 



Mi<-. There is much epidote, which is yellowish and granulated and bunched, 

 but the granules retain their polarizing power, characteristic of epidote. The feld- 

 spars are also deprived of their microlitic shapes, and are scarce, scattered in isolated 

 fragments, there being no ophitic structure preserved. There is much dark Iciico.fciu . 

 and much of the same coloring green chloritic substance, which last is almost mono- 

 refringent between the nicols, and a very little of quartz and of magnetite. One 

 section. 



Age. Archean (Lower Keewatin). \. n. w. 



