324 N. H. WINCHELL ORIGIN OF LAKE SUPERIOR IRON ORES 



discovered and pointed out the ^^glauconite," or greenalite, as one of the 

 phases through which, as he supposed, tlie Mesabi iron ore liad passed. 



Since the date of Spurr^s work (1894) this green substance has been 

 the object of much study. Numerous chemical analyses have shown not 

 only that it is not true glauconite, such as that derived from Forami- 

 nifera, but also that it is a mineral having such definite chemical propor- 

 tions that it is deserving of specific designation. Leith gave it the name 

 greenalite in 1903, in his report on the Mesabi range. 



DiVEEGEXCE OF A^IEWS BETWEEN THE SURVEYS 



Among the divergences which early sprang up between the Minne- 

 sota Geological Survey and the United States Geological Survey, that 

 concerning the origin of the iron ores of the Lake Superior region (espe- 

 cially those of Minnesota) is one of the most important. Those diverg- 

 ences are so numerous and so interlocked, and have become so profound, 

 that many of the final conclusions are widely aj^art, and to one who reads 

 either for the first time, the other appears too much like imaginary 

 romance. Throughout the period involved in this investigation the re- 

 sponsible geologists have aimed to depend usually on fact or on legitimate 

 inferences from fact, and, so far as the writer is concerned, he has never 

 knowingly misrepresented the fact reported by another, nor the state- 

 ments of another based on such fact. Unfortunately, however, his views 

 and his statements have been peculiarly liable to misunderstanding and 

 hence unintentional misre|)resentation. This is so remarkable that the 

 writer's theory of the agenc}'' of igneous rock in the origination of the 

 iron ores has beeu distorted and discarded, although nearly allied {u one 

 that is set up in its place, and identical with it so far as they run ])ai'allel. 



X. H. WixciTELLs S'rr'DiER OF Basic Tfjxi.ors Iiocks 



In 1899 the writer became convinced of the immediate connection of 

 basic Igneous rock with the origination of the ores of Minnesota. This 

 was published in 1900,^^ and it was the first published statement of that 

 broad generalization. '^J'his connection involved igneous eruption, sedi- 

 mentation, and segregation from the parent rock of the concerned iron 

 ore. The igneous rock was shown to be originally in the form of basic 

 lava, often consolidated in the form of obsidian. This rock was con- 

 sidered the first carrier of the iron. It was attacked by the waters of the 

 ocean, torn into fragments by the action of the beach, and its debris dis- 

 tributed as detrital sediment. Cotemporary with this distribution, the 

 oceanic water probably being hot, this igneous rock, whether lava or 



" Final Report of the Minnesota Geological Survey, vol. v. 



