8 XEW YORK STATE MUSEUM 



NATURE OF THE PROBLEM 

 The problem of the genesis of the ores falls into three parts, 

 involving different methods of study. First, and most fundamental, 

 is the study of the general geology of the region in which the 

 deposits occur; for here, as elsewhere, the ores are merely a minor 

 and special product of the geological agents and conditions con- 

 trolling the development of the region as a whole. Second, is the 

 determination of the form, size and structure of the ore deposits 

 themselves and their relations to the immediately surrounding rocks. 

 Third, is the laborator}' study of the ores, their chemical and 

 mineralogical composition and the interrelations of the minerals 

 in a minute way, as shown by microscopic examinaton. 



In the paper above referred to, I\Ir Xewland has discussed the 

 first two phases of the problem at length and the third phase more 

 briefly. The latter is here considered with more detail and, as will 

 be seen, the conclusions reached are in close agreement with 

 Xewland's. 



RESUME OF GEOLOGICAL FEATURES 



The area whose general geolog}^ underlies the problem is, broadly 

 spealdng, the whole Adirondack region, which has been studied by 

 a number of geologists, during a long period., with the resultant 

 determination of the major features of its geological history. 



More specifically, it is the belt of rocks within which the ore 

 deposits lie, together with the closely adjoining formations, whose 

 histor}- is involved in that of the ores ; and the results of the study 

 of these rocks have already been given by 'Mr Xewland. But, as is 

 evident, these rocks can be clearly interpreted only by comparing 

 and correlating them with the formations of the larger region. 



The salient facts of the geolog}' of the Edwards district, from the 

 standpoint of the genetic problem, may, to advantage, be repeated 

 in this immediate connection. 



The ore deposits occur in a belt of thoroughly metamorphosed 

 limestone, with minor amounts of schist, quartzite etc. On the 

 north this limestone is overlaid by schists, apparently part of the 

 same sedimentary series and, like the limestone, thoroughly meta- 

 morphosed. These schists are cut by dikes of pegmatite and granite 

 and thoroughly injected by granitic material, often taking on the 

 character of typical injection gneisses. 



To the south of the limestones (which, with the schists and 



