EARLE, INTERBEDDED IRON ORE DEPOSITS 131 



filtered out of the bed, otherwise the pei'centage of iron in the bed would not 

 diminish below drainage level. 



"Wherever the ore is valuable the inclosing rocks are very much weathered ; 

 the lime rocks are changed into clay and the shales overlying the ore are 

 bleached almost white; their iron having presumably been transferred to the 

 ore bed. And this is a reasonable way of explaining the fact that the ore bed 

 does not always keep the same place in the series, for any bed can become an 

 ore bed, provided it is so situated as to be a water-bearer and recipient of the 

 iron-leachings." 



A. F. Foerste (110, pp. 38-39) : 



"As a rule the iron has replaced the substance of the bryozoan itself; all 

 the stages between partial and complete replacement may be noticed, the most 

 complete stages being of course found in the purer ores. Usually, correspond- 

 ing changes are observed in the cement Avhich binds the oolitic grains together 

 into a solid mass. It is evident in these cases that the origin of the oolitic 

 structure is not due to a concretionary segregation of iron particles, but finds 

 its explanation in the gradual replacement of the lime of the fragmental fossil 

 bryozoans, particle by particle, by the iron ore." 



N. S. Shaler (303, p. 163) : 



"The ores were not included in the present iron-ore beds at the time of their 

 deposition, as conditions varied so much at different points that this would 

 have been impossible. The ore-occurrences are due to replacement of limestone 

 beds by iron-bearing solutions derived from overlying shales. The iron could 

 not have been deposited as far from the shore as the limestones were." 



J. P. Kimball (190, p. 355) : 



"Parts of thin fossiliferous limestones of the Clinton group of strata are 

 often replaced by red and bi'own ferric oxides from extraneous sources. 



"This replacement has been wrought especially in steep dips by infiltrations 

 from drainage of adjacent ferruginoiis strata, partially of an inferior series 

 outcropping topographically higher in the flanks of these parallel ridges." 



Application of Recent Investigations 

 theory of original sedimentation 



Even though it may be demonstrated that the oolitic hematite can be 

 successfully synthesized in a chemical laboratory in open agitated water; 

 even though oolitic formations such as the sand of the Great Salt Lake 

 in Utah and the brown iron oolites of the Swedish lakes are being formed 

 in open water to-day ; yet no matter how plausible the theory may be in 

 most respects, if a single factor prevails that would be impossible under 

 conditions necessary for original deposition of the iron ore beds, it is 



