THE EASTERN AREA. 365 



which contains frajicnients of jftsper, quartz, ami feldspar interlaminated 

 with narrow suanis ot" jarsper whicli appear to be uonfragnieiital. It is' 

 of course possible that the iron-bearing rocks proper occur in Sees. IJ) 

 and 30, but explorations have not yet developed the fact. So far as we 

 are able to jndge by present knowledge the belt which in Sees. 20 and 

 2!) is largely a nonfragmental sediment becomes to the west in the next 

 sections largely a mechanical sediment. . 



Prohahility of ore deposits in the eastern area. — We are now in a position 

 to judge as to the probability of finding iron ore in paying qnantities 

 in the eastern area. The position of the ore de})osits in the main area to 

 the west and the conditions which favor their concentration have been 

 discussed. It will be remembered that they in general rest upon a frag- 

 mental foot-wall quartzite, and that the concentration has been possil)le 

 because of the penetrability of the layers of the formation by percolating 

 waters combined with the impervious character of the belts of rock north 

 and south of the Iron-bearing member, as well as the presence in a pecu- 

 liarly favorable condition of numerous impervious dikes. In the eastern 

 area it is evident that none of these conditions are found. In the fii:st 

 place the original iron carbonate, instead of being deposited in a single 

 homogeneous belt 800 feet in thickness, is scattered through a much greater 

 thickness of rock, part of which is more largel}^ a fragmental than non- 

 fragmental sediment. Second, the different layers of the iron-bearing rock 

 which are purely nonfragmental are separated from one another by almost 

 impervious layers of chloritic and clay-slates or eruptive outflows; so that 

 it is not possible for the concentration to have gone on as a unit, as in the 

 western area. Instead of having a single impervious basement for the non- 

 fragmental rocks we have several or many such basements. In each one 

 of these narrow belts there could have been but a scant supply of iron 

 carl)onate from which iron ore deposits could have formed. It would thus 

 follow that if concentration has taken place in these belts the deposits 

 there formed would l)e of small size. Again, many of the rocks of the 

 iron-bearing belt in the eastern area belong to the actinolitic slate type. 

 It has been already noted that in the main area, where the ore fonnation is 

 mainly ot this type of rock, no ore deposits have been discovered. Finally, 



