22 OUTLINE OF MONOGRAPH. . 



erogenic movements that have occurred since its deposition. In consequence of this 

 its rocks have been most intricately folded. Where it is exposed most prominentl}^ 

 it forms anticlines, although upon these are numerous minor rolls, giving folds with 

 steep pitches. The formation consists of (1) a very subordinate fi'agmental portion 

 made up of some conglomerate, clearly recognizable as having been derived from 

 the underlying greenstones, grading up into sediments of finer character; and (2) 

 lying above this fragmental portion, the iron-bearing formation proper, which 

 consists of siliceous rocks, largely white cherts — though varying in color from. white, 

 green, yellow, and purplish to black — with red jasper and carbonate-bearing chert, 

 griinerite-magnetite-schist, hematite, magnetite, and small quantities of pyrite. 

 These various rocks occur in bands of varjdng thickness. Where banded thej' 

 rai'ely exceed a thickness of 6 or 6 inches. The hematite occurs in certain places 

 in masses of variable size, which constitute the ore de^josits. These iron-bearing 

 rocks are clearlj^ of sedimentarjf origin. They do not now present their original 

 characters, but are presumed to have been derived from rocks that were largely 

 carbonate-bearing, ferruginous cherts. The relation of the iron formation to the 

 adjacent greenstones is clearlj'' that of a sedimentary overlj'ing an igneous series. 

 The few basal conglomerates of the iron formation that have been found consist of 

 pebbles derived from the underlying greenstone, showing conclusively' their relation- 

 ship. This relationship is obscured, however, in most places, bj' ,the absence of 

 the conglomerates, and bj' the fact that the iron formation has been very closelj' 

 infolded in the greenstone. In consequence of the extreme folding and of the 

 impossibility of determining different horizons in the iron formation, it has been 

 impracticable to ascertain its thickness. 



The first published statement of the occurrence of iron ore in the Vermilion 

 district was made by J. G. Norwood in 1850. After a brief period of exploration 

 for gold in the sixties the attention of explorers was turned to the development of 

 the iron deposits. As the result of this development a railroad was built to Tower 

 in 1884, and shipments of the ore began. The ores are extremelj^ hard, massive, 

 blue hematites. In the Chandler mine the ores have been brecciated, but the 

 fragments of the breccia are still the hard blue hematite, averaging about 63.7 per 

 cent iron, 0.05 per cent phosphorus, 1.78 per cent silica, and 5.5 per cent water. 



The iron-ore deposits of the Vermilion district show a striking analogy with 

 those of the Marquette district. Like them, the^' ma}' occur in two positions with 

 respect to the iron-bearing formation. Thej' are found first at the bottom of this 

 formation, and second within it, the 'ores in both cases being the same in character. 

 The largest known deposits are at El}'. These are tj'pical of the deposits occurring 

 at the base of the formation. They are found at the bottom of a closely compressed 

 syncline of the iron formation which lies in the relativelj' impervious greenstone. 

 The source of the iron was, in the first instance, the Ely greenstone. From this 

 it was removed through the action of water and collected in the Archean sea to 

 form the sedimentarj' deposits of the Soudan formation. After the folding of the 

 formation this disseminated iron was carried by downward-percolating waters. into 



