68 Minnesota Academy of Science 



,i I, so far as exploited, it is nonlbessemer. Sulphur is present 

 in the gangue. but not notable in the ore itself. 



The ore is principally limonite.* 



The ore is never conglomeratic but is associated with some 

 paint rock. This paint rock is not known to be a fragmental shale, 

 like the paint rock of the Mesabi, and is comparatively scant. 



The ore is not granular, but massive, previous to mining, and 

 the rock taconyte has not as yet been met with. 



As to the Associated Rocks. 



The position of the formation is nearly or quite vertical. The 

 rocks are metamorphic, and sometimes may be called crystalline. 



They are largely of greenstone, or green schist. Both granite 

 and a line silky mica schist are found on the Cuyuna range, the lat- 

 ter in many drill holes. 



In some instances a carbonaceous (graphitic) black slate has 

 been found on the Cuyuna range, but its structural relations are un- 

 known. It may be due to early igneous action, but it has not been 

 found to be referable to volcanic debris, like the slates of the Me- 

 sabi range. 



The ore is sometimes associated with jasper, but not to a mark- 

 ed extent. It is identical with the jaspilyte of the Vermilion. 



These answers are based on what is now known of the Cuyuna 

 range, and are liable to correction as new discoveries are made, 

 but it is not at all likely that such discoveries will change the gen- 

 eral purport of present evidence. 



It is hardly necessary to state that the testimony of these ans- 

 wers is overwhelmingly in favor of the Archean age, and .hence in 

 favor of the Vermilion range. It would be vain, therefore, to search 

 for the Mesabi ore, or any ore like the Mesabi ore, in the Cuyuna 

 range as now developed. 



There is still one important proviso that ought to be mentioned 

 in favor of the possible discovery of the Mesabi ore on the Cuyuna 

 range, viz: at some places on the Cuyuna range some of ttie red 

 shales, and the igneous conglomerates characteristic of the Mesabi 

 ores, have been discovered by diamond drilling. Such red shale 

 was found near the west end of Dam lake, having a thickness of 

 thirty feet, and the igneous conglomerate (or breccia) was found 

 at eight miles east from Brainerd. These indicate the extension of 

 the igneous rocks of the Mesabi over some part of this region, and 

 it would be wise for future explorers to give careful heed to these 

 discoveries, to the end that an extension of the Mesabi ore may be 

 brought to light. 



The first discovered of the Iron ranges was Marquette, and at 

 that place for some years ore was mined from rocks of both ages 

 before it was found that both existed in the limits of the range. It 

 seems very likely now, that the Cuyuna, the newest of the iron 

 ranges discovered, may duplicate Marquette in having both repre- 

 sented, and that Aitkin fifty years hence will be as far-famed as 

 Marquette is todav. 



* Latterly the ore of the Cuyuna has been found to consist large- 

 ly of hematite. 



