Iron Ore Ranges of Minnesota. 



47 



Fig. 4. — Mica schist intruded by granite 



(4) The next slide shows some of these recrystallized sedi- 

 mentary rocks. The original sediments, represented now by the 

 mica schist, were penetrated and crossed by granite in diagonal in- 

 trusions and in parallel laminations. This granite is not supposed 

 to have come from a deep-seated source, but from some nearby lo- 

 cality where the original rocks were fused, or at least plastic so as 

 to enter any cracks that were formed in the adjacent sediments. 



This vertical attitude of the strata is seen at all the open mines 

 in the Vermilion range. Here however the original rock was not 

 an acid sedimentary one ; but a basic igneous one. Outside of tin 

 mines, at short distances to the north or south, however, this igneous, 

 basic, green rock is replaced by acid sediments. It is a very sig- 

 nificant and remarkable fact that the ore of the Vermilion iron range 

 is in a basic igneous formation, one which has been called "Kawish- 

 iwin", and that in some cases it is in somewhat regular alternation 

 with layers of such igneous rock. We will not dwell here on the 

 importance of that fact, but will pass at once to some slides that 

 show that structure. 



Fig, 5. — Jaspilyte and Green Schist. 



