52 NEW YORK STATE MUSEUM 



Upon the formation of the ore beds, have been well stated by 

 Professor Smyth in a paragraph of his paper of which the fol- 

 lowing is a translation. 



By reference to a geological map of the eastern United States, 

 it will be observed that the Clinton beds were deposited in a 

 sea which received the drainage from an extensive area of crys- 

 talline rocks. Long continued denundation of these rocks, which 

 are made up in part of iron-bearing silicates and inclose import- 

 ant bodies of magnetite and pyrite, set free large amounts of 

 iron to be carried seaward in solution or suspension. Along the 

 coast of the sea there were in Clinton time extensive swamps 

 and mud flats, evidenced by the frequent surface markings, 

 cracks and tracks of crustaceans and worms found in the 

 shales and sandstones. In other places calcareous fossil frag- 

 ments accumulated and were rolled about and ground by the 

 waves and finally deposited in shallow water forming shell 

 beaches similar to those of the present day, for example, the 

 coquina on the Florida coast. Most of the iron brought down 

 by land drainage of course would be wasted, but a part would 

 be precipitated to form the ore beds. The precipitation occurred 

 in two ways, thereby giving rise to two ore varieties. Where 

 the waters were collected in partially or completely inclosed 

 basins, the iron was thrown down by slow oxidation and gath- 

 ered in layer upon layer about the sand grains, thus forming the 

 oolitic ore. The conditions requisite to this method of precipi- 

 tation obtained apparently over no gre^t areas, so that the oolitic 

 beds are generally of limited extent. Again the ferruginous 

 waters came in contact with the calcareous shell fragments; 

 here the iron was precipitated partly by reaction with the lime 

 carbonate, yet mostly by oxidation, while the lime was carried 

 off in solution by the aid of the carbon dioxid set free. As this 

 process took place while the shells were being rolled about or 

 heaped up in loose aggregates and was chiefly a result of oxida- 

 tion, the iron took the form of oxid rather than carbonate. It 

 need scarcely be stated that this method of replacement is 

 widely different from the other process of replacement that has been 

 applied to the ores. The progress of the reaction advanced step 

 by step with the accumulation of the fossil fragments. Thus, 

 while the iron is a secondary product as regards the individual 

 particles of ore, it is primary in relation to the ore bed itself. 

 After the ores had thus been collected into loosely aggregated 

 masses of grains and altered fossils, -they were compacted into 

 beds and covered by shales, sandstones and limestones. As a 

 result, the grains and fragments rich in iron are frequently sur- 

 rounded by pure calcite, a circumstance that is far from being 

 opposed to the present theory of ore formation, but rather in line 

 with what one would expect. 



