590 THE GEOLOGY OP MINNESOTA. 



No. 885. CHLORITE SCHIST. 



[Chlorite schist. Greenstone. 

 Graywacke. Argillyte. 



North end of a cut on the Duluth and Iron Range railroad, about one-third rnile northwest of the south- 

 east corner of sec. 5, T. 61-15 W. South from Soudan. 

 Kef. Annual Report, xv, pages 270, 388. 



Meg. A fine-grained, soft, green schist. 



M ic. The section shows a schistose rock composed of chlorite, quartz and probably 

 also feldspar. There are varying amounts of calcite, magnetite and epidote. Thickly 

 scattered through the section are minute grains which have a high index of refrac- 

 tion and very weak double refraction; they are probably zoisite. One thick section. 



Age. Keewatin. u. s. G. 



NO. 886. "GREENSTONE." 



South end of the same cut from which No. 885 came. 

 Ref. Annual Report, xv, pages 270, 388. 



Meg. A fine-grained, compact greenstone. 



Mic. The section shows lath-shaped plagioclases in a mass of alteration products 

 composed mainly of green hornblende, chlorite and finely divided magnetite. Calcite 

 is common, and epidote is present. The rock was probably originally a diabase. 



One section. 



Age. Keewatin. u. s. G. 



No. 887. GRAYWACKE. 



Cut on the Duluth and Iron Range railroad; S. E. % sec. 8, T. 61-15 W. South of Soudan. 

 Ref. Annual Report, xv, pages 271, 388. 



Meg. A hard graywacke of medium grain. 



Mic. More or less angular, prominent feldspars and fewer quartzes are 

 embedded in a much finer grained groundmass, although there are grains of sizes 

 intermediate between the grains of the groundmass and these more prominent grains. 

 The feldspars are usually considerably altered and cloudy, though some still show 

 albite twinnings. The groundmass is composed essentially of quartz, feldspar, chlorite, 

 Muscovite and calcite. One section. 



Age. Keewatin. u. s. G. 



No. 888. ARGILLYTE. 



Same place as No. 887. 



Ref. Annual Report, xv, pages 271, 388. 



Meg. A fine-grained, dark-gray, slaty argillyte with mica scales along the 

 cleavage planes. 



Mic. The rock is composed chiefly of fine grains of quartz and probably also 

 of feldspar and flakes of biotite and chlorite. Magnetite and pyrite are present, and 

 there are some minute grains which appear to be epidote. One section. 



Age. Keewatin. u. s. o. 



