SOUDAN FORMATION. 



243 



Statement shoioing -production and ishipments from all Vermilion Range mines since 



ISSJj. — Continued. 



Long tons. 



Total production 19,351,388 



Total shipments 19,120,990 



PROSPECTING. 



From the facts of occurrence given in the preceding pages we are 

 enabled to draw the following conclusions concerning the localities at which 

 prospecting' for ore might be advantageously prosecuted in the Vermilion 

 district. At the outset it may be said that as a result of the mode of forma- 

 tion and occurrence of the ores it is very probable that all of the large 

 ore deposits which exist will somewhere reach the top of the iron formation. 

 However, in consequence of the glacial drift which covers a large portion 

 of this region, the ore deposits rarely reach the present surface of the 

 ground, being buried by the drift. In the case of the deposits at Tower 

 and Soudan, the ore, on account of its exceptional hardness, outcropped upon 

 the tops of the highest hills, which, owing to their height, are, to a very 

 considerable extent, free from the drift. But usually the ore is softer than 

 the adjacent hard jasper and chert and greenstones, and is likely to have 

 suffered more from erosion than these. Hence the ores commonly occupy 

 more or less marked topographic depressions. 



At Ely the exposures were first found at the west end of a broad basin, 

 illustrating what the writer considers the typical occurrence, at least for the 

 east end of the district. Since igneous rocks form the impervious basements 

 upon which the ore deposits rest, it follows that the igneous rocks should be 

 examined with great care, especially where they are impregnated with iron 

 and are in the condition in which they are known as the paint rock. The ideal 



