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NEW YORK STATE MUSEUM 



parallel to the banding, but their general shape, if indeed they have 

 any uniformity, is far less clearly understood than that of the ores 

 in gneiss as they have not yet been much mined. 



GENERAL FEATURES OF THE NON-TIT ANIFEROUS MAGNETITE 



ORE-BODIES 



The common form assumed by non-titaniferous ore bodies, and 

 the one usually associated with gneisses for wall-rock, is that of 

 a bed or flattened lense, or pod, which lies parallel to the general 

 foliation. They show no traces of having filled a cavity, but unless 

 regarded as segregated veins, i. e. as having gathered along the bed- 

 ding by the concentration of iron oxide from the walls, after the 

 manner of a concretion on a grand scale, they must be considered 

 true beds. For the smaller ore bodies in the two towns here 

 described, these general relations and shapes hold good but for the 

 great ore-bodies at Mineville, it is difficult to see how any folding 

 and contortion of simple beds can explain the peculiar and irregular 

 shapes which are later illustrated. They are decidedly abnormal. 

 In the writer's estimation no segregative agency strictly so called 

 could have occasioned them and some other method of origin must 

 be invoked. The true lenses pinch, swell and feather out at the 

 boundaries. They often fork when wedge-shaped masses of the 

 walls come in. They are often distributed along a general horizon 

 in the gneiss, although at times several beds, one over the other are 

 afforded. The long axis of the ore-body does not run straight 

 down on the dip, but diagonally, and this inclination is called the pitch 

 in distinction to the true dip. The rule already formulated in New 

 Jersey also holds good in the Adirondacks, that with a westerly dip 

 the pitch is to the southwest, and with an easterly dip the pitch is 

 northeast. 



DETAILED GEOLOGY OF THE IRON ORES 

 The Mineville and Barton Hill Groups. The topography of 

 this district may be seen from the accompanying map. As already 

 stated the Barton Hill group occurs at a higher horizon in the gneisses 

 than the Mineville group, but just what it is in feet is hard to say, for- 

 there is a fold or crumpling between. As shown by the table the 

 ores are contrasted in composition, the lower series being much 

 higher in phosphorus. Almost no sulphur occurs in either, and 

 titanium is insignificant. 



