IRON ORES OF THE CLINTON FORMATION 5 1 



mining, by which the overlying burden is removed over a con- 

 siderable area before the ore is taken out; the surface of the 

 stratum is extremely regular and smooth, not less so than the 

 surface of the superincumbent limestone. 



In their uniformity of character the hematites possess a fea- 

 ture that is consistent only with a sedimentary derivation. This 

 uniformity holds true for the beds near the surface and also 

 with regard to the ores encountered at depths of several hun- 

 dred feet from the surface. The recent exploration with the 

 diamond drill has shown that there is no notable change of 

 character on the dip for distances of 5 or 6 miles from the out- 

 crop. Deep borings made some years since at Syracuse and 

 Chittenango found the hematite below 600 feet showing it to be 

 of normal composition.^ The ores hold out to much greater 

 depths than could be expected from the work of underground 

 waters. 



Enrichment by solution and redeposition of the iron has not 

 occurred in the New York beds. Whatever variation in iron 

 content there may be is to be regarded as original or as due 

 to weathering on the surface. There are no bodies of soft ores 

 at all comparable to those found in the southern districts. This 

 may be ascribed in large measure perhaps to the effects of the 

 glacial invasion ; during the long period previously in which the 

 beds were exposed to atmospheric agencies it seems likely that 

 the ores may have weathered for some distance from the out- 

 crop but were planed off by the ice in its southward advance. 

 Yet, the horizontal disposition of the beds has no doubt retarded 

 disintegration. The chief eff'ect of weathering is the removal 

 of calcite which cements the particles of hematite. 



The physical constitution of the hematites has already been 

 described and need not be considered in this connection further 

 than to allude to the almost universal presence of oolitic grains 

 in the ores, even those which are apparently of purely fossilifer- 

 ous nature. The deposition of iron about a nucleus in layer 

 after layer can scarcely be conceived as taking place elsewhere 

 than in bodies of standing water, with the nucleal grains free 

 to roll about and completely in contact witli the ferruginous 

 solutions. 



The probable conditions prevailing in Clinton time, bearing 



* C. S. Prosser. The Tliickness of tlic Divoiiiaii and Siliii iati Ixorks in Central 

 New York. Geol. Soc. Am. Bui..): 91. 



