28 NEW YORK STATE MUSEUM 



There seems to be no doubt that the blende has shared in this 

 process and, consequently, in its present condition is a precipitation 

 from descending surface waters. 



In other words, the blende of this deposit is ascribed to such 

 conditions as produce the " secondary enrichment " of copper ores 

 rather than to the much deeper seated conditions represented by the 

 other zinc ores of the region. Obviously, if this interpretation is 

 correct, the blende in question is vastly younger, in its present state, 

 than the blende of the other deposits. 



As this younger blende is all light colored, it might be taken as 

 evidence that the small quantities of light blende in the other deposits 

 were of the same late and superficial origin. Reasons have already 

 been given for believing that this is not the case and an added 

 argument against this supposition is afforded by the fact that, in 

 the one case where it appears to be evidently applicable, the cond'- 

 tions implied by it have completely changed the character of the ore 

 deposit, making it wholly dissimilar to the ordinary zinc ore else- 

 where in the region. The latter shows no features that suggest any 

 extensive action of superficial waters such as have so thoroughly 

 made over the Sylvia lake deposit. 



Thus, while the latter deposit shows that there has been, in this 

 particular instance, a transfer and redeposition of blende by super- 

 ficial waters, acting geological ages after the primary deposition of 

 the mineral, this does" not indicate that the same action is account- 

 able for the small quantities of light-colored blende associated with 

 primary blende in the ordinary ore deposits. While this light- 

 colored blende is, obviously, somewhat younger than the dark 

 mineral, the age dift'erence appears to be slight and both types are 

 regarded as belonging essentially to one period of ore formation or, 

 in other words, to continuous and practically uniform geological 

 conditions. Any solution and redeposition of blende that has 

 occurred is ascribed to the action of the normal vein-forming solu- 

 tions rather than to superficial waters of later date. This is, how- 

 ever, a question in regard to which there is room for much differ- 

 ence of opinion and Newland ascribes the later blende to superficial 

 waters. 



To summarize briefly : The ore deposits are of high-temperature 

 type, with the sequence — anhydrous silicate, sulphides, hydrous 

 silicates, or, in more detail, (i) diopside, tremolite, (2) pyrite, 

 (3) blende, (4) galena, (5) talc, (6) serpentine, controlled by 

 decreasing temperature. Throughout the process of mineral forma- 



