770 THE GEOLOGY OP MINNESOTA. 



[Granite. Mica schist. 



Mic. The coloring element is green hornblende in irregular small shreds (with 

 one or two grains of zircon} and a small amount of hematite. There are two or three 

 feldspars and some quartz, all united in a fine, uniform, granular structure. One 

 feldspar is filled with inclusions, largely of mica, but sometimes of epidote, hornblende 

 and apparently of another feldspar. The feldspathic substance that now occupies 

 these grains has a higher refractive index than quartz and is probably andesine. It 

 is sometimes coarsely twinned. The fresh feldspars are microcline and apparently 

 albite and oligoclase. One section. 



Age. Archean. N. H. w. 



No. 1726. GRANITE. (Augttic. ) 



Appearing in irregular patches, somewhat dike-like, in No. 1725, though these two rocks apparently grade 

 into each other. 



Ref. Annual Report, xxi, page 156. 



Meg. Intrusive granite. 



.Mic. This rock is much like No. 1725, but is coarser grained. It also contains 

 sphene, while the hornblendes are replaced by augite, which is green, and appears like 

 hornblende. The microcline exhibits microperthitic and other intimate relations to 

 small grains of other feldspar, often surrounding them in a poikilitic manner. One 

 section. 



Age. Archean. N. H. w. 



No. 1727. GRANITE. (Augttic.) 



S. W. % sec*. 26, T. 64-9, Snowbank lake, near No. 1726. 

 Ref. Annual Report, xxi, page 156. 



Meg. As a dike, cuts the crystalline condition of the conglomerate, contact 

 running about east and west. 



Mic. Like No. 1726, but contains also a little hornblende. One section. 

 Age. Archean. N. H. w. 



No. 1728. MICA SCHIST. 



S. W. 14 sec. 26, T. 64-9, north shore of Snowbank lake. 

 Ref. Annual Report, xxi, page 156. 



Meg. A micaceous, fine-grained condition of the conglomerate (No. 1724), cut 

 by granitic dikes. There is a distinct dip visible on the tops of the knobs (E. S. E.), 

 and the strike is 15 E. of N., the dip throwing the rock under the granite. Not 

 schistose. 



M/r. This rock differs from rock No. 1724 only in the following respects: Less 

 hornblende, considerable mica (biotite), greater invisibility of many of the old feld- 

 spars, absence of quartz, and the greater number of the "globular feldspars," which 

 last character gives the finer parts of the slide a granulitic, interlocking structure. 



