24 NEW YORK STATE MUSEUM 



Adirondacks. This is attributed to the more thorough explora- 

 tion of the outer areas owing to the advantages they afford in 

 regard to accessibility for prospecting and transport of the ore to 

 the market. No doubt the explanation is a reasonable one and 

 entitled to serious consideration. But it would seem not improb- 

 able that there is an underlying geological basis for the gen- 

 eral distribution of the occurrences that may be brought out 

 clearly when the region is mapped in detail. The present study 

 has not been extended beyond the limits of the ore-bearing dis- 

 tricts. The interior of the Adirondacks is occupied in part by the 

 great anorthosite mass, within which the ores are all titaniferous. 

 Of the extensive region to the west and south of this area to near 

 the Adirondack borders little is known as yet concerning its 

 geology. 



By far the greater number of mines that have been worked, 

 including all the important ores, are restricted to a few districts 

 of comparatively limited area. The total surface embraced within 

 these districts constitutes but a very small portion of the whole 

 region. It is probable that future exploration when extended 

 into the outlying areas will result in the addition of new deposits 

 to the list; but it can hardly be expected that the discoveries will 

 compare in importance with those already made. The favorable 

 ground for development was sought out by the early prospectors 

 who seem to have penetrated into the most remote parts in their 

 search and to have made good use of the dip needle and compass, 

 by w r hich the location of highly magnetic bodies like these is a 

 comparatively easy matter. 



Character of the ores 



The ores show great variation in their mineral and chemical 

 composition. They range from impure lean varieties consisting of 

 magnetite intermixed with the constituents of the wall rocks, such 

 as quartz, feldspar, pyroxene, hornblende etc., to those made up of 

 practically pure magnetite. The richest average from 60 to 70 per 

 cent iron. They have been obtained principally from the Mineville 

 district, where some large bodies have averaged 60 to 65 per cent 

 iron and have afforded considerable quantities assaying above 65 

 per cent and even approaching closely the theoretical limit for 

 magnetite which is 72.4 per cent. The Hammond ville, Arnold 

 hill and many other mines have yielded ores with 50 to 60 per cent 

 iron. The magnetites that carry less than about 50 per cent iron 



