2(i NEW YORK STATE MUSEUM 



the talc and in the same geological surroundings, is a noteworthy 

 feature which has only recently attracted attention. The ores form 

 pockets and bands in limestones and schist with the characteristics 

 of replacement deposits. In any case, they have undoubtedly been 

 introduced in solution and precipitated in their present place after 

 the upraising of the sediments represented by the wall rocks. It 

 would appear probable from these and from other- considerations 

 which need not be entered upon here that there is a close genetic 

 relation between the talc and the metallic minerals. This point is 

 of some significance in regard to the probable extent of the talc 

 deposits and renders a more detailed investigation of the field highly 

 desirable, 



Zinc. A brief visit to the zinc ore localities of St Lawrence 

 county was made during the summer for the purpose of studying 

 the occurrences and securing material for the collections. There 

 has been much activity in prospecting within the district, but the 

 recent developments have been restricted, as in the previous year, 

 to the locality near Edwards. As the result of recent discoveries, 

 it is known that zinc blende has a rather wide distribution in the 

 section from Edwards to Sylvia lake, which is practically coextensive 

 with the talc district. The economic importance of the deposits is 

 scarcely to be estimated as yet, but the work on the single property 

 that is under exploration, lends encouragement to the hope that a 

 substantial industry may be developed. Some difficulty has been 

 encountered in the mill treatment of the ore which contains more 

 or less pyrite in intimate association with the blende, the two min- 

 erals occurring usually in finely divided intergrown particles. 



Field observations show that the blende is found in crystalline 

 limestones of the same belt that includes the talc and tremolite 

 beds. The limestone belt is interrupted here and there by bands 

 of rusty, quartzose schists, and by dark basic hornblende and biotite 

 gneisses. The rusty schists are very certainly a part of the same 

 sedimentary series representing probably old sandstones, while the 

 hornblende and biotite gneisses also are believed to be derived from 

 sediments of the nature of shales, though in places they may repre- 

 sent altered igneous intrusions of gabbroic nature. The gneisses 

 and schists have been invaded by a red granitic rock, with pegmatitic 

 phases, that is developed in dikes, bands and occasionally as bosses 

 of some size. The granite is perhaps related to the great batholiths 

 of that rock which are found in the interior of the Adirondacks. 

 The gneisses have been so injected and soaked by the granite that 

 in places they partake quite as much of igneous as of gneissic 



