96 IRON ORES OF IRON SPRINGS DISTRICT, UTAH. 
iron formation is regarded as a prerequisite for exploration for iron ore. 
The Iron Springs deposits lack an associated sedimentary iron forma- 
tion to serve as a guide for exploration, though there are locally pre- 
sent lean phases of ores for which the term "iron formation," without 
genetic significance, might be appropriate. The deposits themselves 
in the Lake Superior region rest in structural basins which determine 
for each district certain uniformities and peculiarities of shape for the 
ore deposits for that district. For the Lake Superior region as a 
whole the variety of shapes of ore deposits is probably greater than that 
in the Iron Springs district, but the Iron Springs deposits probably 
have a shape and size which can be less safely predicted in advance of 
exploration than can those of the deposits of any one of the Lake 
Superior districts. They have, however, one considerable advantage 
in that they are largely exposed on the erosion surface, whereas the 
Lake Superior deposits are in great part covered by glacial drift. 
