912 THE GEOLOGY OP MINNESOTA. 



[Schist. Greenwacke. Graywacke. 

 Greenstone. 



No. 89W. SCHIST. ( Sericitic. ) 



S. E. y S. E. J^ sec. 29, T. 63-12, main land, shore of Long lake. 

 Ref. Annual Report, xv, page 55. 



Meg. Coarse, gray, schistose. 



Mic. The same fine interlocking groundmass of fresh quartz and feldspar 

 embraces feldspar and augite forms, but in place of feldspar and augite are now other 

 minerals, viz., in place of feldspar muscovite and calcite, with considerable chlorite, the 

 two former in unusually large grains, and in place of augite is chlorite. There is 

 also in general much epidote, sometimes in grains of size sufficient to give colored 

 polarization. One section. 



Arje. Archean (Keewatin). N. H. w. 



No. 91W. GREENWACKE. 



Centre of N. E. % see. 28, T. 63-12, Long lake. 

 Ref. Annual Report, xv, page 55. 



Meg. Chloritic graywacke. 



Mic. A confused mingling of fine feldspars and quartz, with abundant hornblende, 

 c-alcite and leucoxene, and with epidote. In the slide are inequalities of grain and in 

 the distribution of the hornblendes, denoting the former existence of other minerals, 

 probably of feldspars, which have been absorbed and replaced by a fine micro- 

 granulitic growth, such as is common in old greenstones. In other places remnants 

 of such old feldspars are still visible. The rock was probably at first a debris of 

 basic composition, perhaps tuffaceous. One section. 



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



No. 92W. GRAYWACKE. 



S. W. y S. W. Ji sec. 23, T. 63-12. 

 Ref. Annual Report, xv, page 55. 



Meg. Graywacke. 



Mic. Similar to 91 W, but much lighter colored, having no hornblende, little 

 chlorite, and much better preserved feldspars, but the rest of the slide is largely 

 ' composed of a tine quartz-feldspar secondary replacement, which is irregular in 

 fineness, indicating that the rock was originally fragmental. 



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



No. 94W. GREENSTONE. ( Altered dibuxe.) 



S. E. % S. W. Yi sec. 20, T. 63-11, Garden lake. 

 Ref. Annual Report, xv, page 68. 



Mic. The feldspar is almost wholly destroyed, its place being occupied by saus- 

 suritic products, largely epidote. Hornblende is abundant, but is frequently replaced 

 by a later isotropic chloritic substance. There are large angular masses of leucoxene 



