244 THE VERMILION IRON-BEARINQ DISTRICT. 



condition for the accumulation of ore is, as has been shown, a pitching troug-h 

 of greenstone, with a great thickness of fractured jasper lying in it. The 

 most favorable conditions for the formation of an ore body or ore bodies of 

 some size are present where there is an amphitheater of greenstone within 

 which lies the jasper, in a much crumpled and fractiired condition, with the 

 axes of the synclines plunging toward the opening of the amphitheater of 

 greenstone. Unfortunately, even when these favorable conditions are 

 found, only exceptionall}^ has the accumulation of the ore taken place. 



The size of the ore bodies varies much as the result of a number of 

 factors, but one can state with confidence that the larger the amphitheater 

 and the larger and thicker the mass of iron formation, and the fewer the 

 dikes contained within this formation — whose effect would be to subdivide 

 the large pocket into a number of smaller ones — the more likely will an 

 ore deposit found prove to be a large one. 



The Tower and Soudan deposits are in synclines which occur on the 

 top of anticlines, forming hills. As the result of this known occurrence, 

 the prospectors have appeared very generally to neglect explorations in low 

 ground. But there are a number of areas of low ground that are with 

 great degree of probability underlain by the iron formation, and some of 

 them possibly by iron ore, which should be explored, for, as already noted, 

 where the ore is soft it is generally found to occupy the lower areas. The 

 difficulties attending prospecting- in these low areas are great, on account of 

 the water and the deep drift frequently found in them; but they may 

 contain ore deposits which will pay in proportion to the difficulties 

 attendant upon their discovery. It may be well to call to mind the fact 

 that some of the large deposits occurring in Michigan — for instance, the 

 Aragon mine of the Menominee range and the Lake Ang'eline of the 

 Marquette range — are found in such positions. 



But it should be emphasized that, as a matter of experience, no large 

 ore deposits have been found except where the iron-bearing formation has 

 considerable breadth. At many points the favorable conditions mentioned 

 above, except the presence of broad bands of the iron-bearing formation, 

 have been found ; but in no known case where the iron formation is narrow 

 have such localities yielded workable ore deposits. Certainly experience 

 in the Vermilion district does not justify the expenditure of money in 

 exploring the narrow bands of jasper. Many thousands, probably hundreds 



