USEFUL METALS 



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Keweenawan by another unconformity. The Keweenawan 

 formations consist of gabbro and granite intrusives in all of t In- 

 lower formations. All of the foregoing rocks are separated from 

 the Cretaceous by another unconformity. 





The Biwabik iron formation forms a continuous belt from 

 Grand Rapids on the west to Birch Lake on the east. Its breadth 

 varies from a quarter of a mile to more than two miles. It pre- 

 sents four widely different varieties of ferriferous rocks. (1) 



