PETROGRAPHIC GEOLOGY AND DESCRIPTIONS. 933 



ynartzyte. Hornblende schist.] 



set with granules and minute groups of side-rite, the light which passes is sufficient 

 to make the field quite illuminated. This slide shows a condition of the iron ore of 

 the Mesabi range. One section. 



Age. Animikie. 



Remark. Macroscopically this sideryte forms granular bands or layers alter- 

 nating with hematitic layers, the whole being probably originally water-deposited, 

 but the hematitic bands cotemporaneously mingled with more volcanic ash and 

 devitrified glass. This sideryte exists in quantities sufficient to make it of commer- 

 cial value. It has the outward appearance of a fine, gray, stratified sand. N. H. w. 



No. 205S. QUARTZYTE. 



N. W. M N. W. ^ sec. .">G, T. 58-21, Mesabi range. 

 Ref. Annual Report, xxii, page 132. 



Granular quartzyte, grayish red. 



Mic. Originally clastic, round grains of quartz have been enlarged by secondary 

 silica in crystalline agreement with the various grains, making a compact rock. 

 Amongst these are a few of microcline and of other feldspars equally rounded but 

 not apparently enlarged. There is a dark narrow border of rejected debris which 

 separates the enlarged grains from each other, and a less distinct one that separates 

 the original grains from their enlargements. One section. 



Age. Pokegama (base of the Animikie). 



Remark. The "rejected debris" mentioned is sometimes in roundish shapes as 

 if it had constituted original grains. It appears to be devitrified glass. It is usually 

 crowded with indistinct, minute crystalliths and is largely isotropic. N. H. w. 



No. 226S. QUARTZYTE. 



S. W. y N. W. y sec. 35, T. 58-21. 

 Ref. Annual Report, xxii, page 133. 



Meg. Gray quartzyte. 



Mic. Similar to No. 205S, but less coarse. The intergranular substance is 

 green and apparently chlorite, and more abundant than in No. 205S. There are also 

 a few minute zircons. One section. 



Age. Pokegama (base of the Animikie). 



Remark. This greenish substance is finely scaly, like chlorite. It may have 

 resulted as a detritus from ferromagnesian Archean rocks. N. H. w. 



No. 227S. HORNBLENDE SCHIST. 



N. W. y^ N. W. J4 sec. 35, T. 58-21. 

 Ref. Annual Report, xxii, page 133. 



Meg. Fine, dark, schistose, hornblendic. 



