l82 NEW YORK STATE MUSEUM 



conditions, whether through the intervention of magmatic or of 

 meteoric waters or both. 



In view of the nature of pyrite, it is probable that the general 

 tendency during these operations has been toward concentration 

 rather than dissipation, and it is possible that workable deposits 

 might result. But, as shown above,, there is reason for believing 

 that in the final stage at least, pyrite has been added from external 

 sources. 



While, on the assumption that the four periods of concentration 

 are well established, there is stiir room for much difference of 

 opinion as to their relative importance, from what has been said 

 above it is evident that the writer regards original sedimentation 

 as merely of potential importance affording only disseminated pyrite 

 which would demand great concentration to be available. Such 

 concentration may have been effected to a considerable degree in 

 the hypothetical second or ground-water period, was probably not 

 greatly influenced in the third or metamorphic period, and was 

 chiefly accomplished in the fourth or postmetamorphic period, 

 during which, minerals formed in the third or metamorphic period 

 were broken down and replaced by others, of which pyrite is the 

 most important. That much of the pyrite was actually deposited in 

 its present form and place during this period is certain, that the ore 

 bodies are to a large degree the products of this deposition is the 

 conclusion reached from the evidence now available. 



