MAGNETITE IRON DEPOSITS OF SOUTHEASTERN NEW YORK 103 
surrounded by the ore are frequently encountered. Newland **’ 
states, in discussing the ore of the Forest of Dean mine: “ Some 
sorting is necessary on account of admixture with granite which is 
found in stringers and small bodies within the deposit, and is of the 
same character as the granite that divides the two wings.” 
The rock thus found is not granite; it is Pochuck-Grenville, which 
is at times highly pegmatized, and always more or less profoundly 
affected by the end-stage emanation processes that gave rise to the 
magnetite. A sample of rock included in the ore on the sixth level 
carries pyroxene, now wholly altered to either sericite or fine flaky 
talc, and fine dusty carbonate, feldspars more or less sericitized, 
biotite, quartz with replacement aureoles of sericite surrounding it, 
and much magnetite (see plate 7, figure 3; plate 10, figure 3 and 
plate 11, figure 1). Sometimes the included rock is a streak or 
bunch of pegmatite, occupying a sort of pocket in the magnetite. 
Here are found masses of coarse pink calcite mixed with anhydrite, 
feldspar, generally plagioclase, coarsely crystalline magnetite in large 
grains, green pyroxene and apatite, the whole related to the 
pegmatite and a part of it, the magnetite always existing in end- 
stage relations. 
These features seem to support not only the postulated close rela- 
tionship between the pegmatite and magnetite, but also the assumed 
magmatic end-stage emanation origin of the magnetite, and magmatic 
end-stage deuteric replacement. 
g Persistence of form and cross-section. This is indeed a remark- 
able thing; not because the magnetite persists in depth, for that may 
well be expected in a deposit of magmatic origin, but because of the 
retention of shape and cross-section which is difficult to explain; 
the slope has now been sunk 4500 feet, without any indication of 
change in the form or in the quantity of the ore. If one can imagine 
this body of magnetite as restored to place, and then pulled out of the 
ground as one would pull out a stake which had been thrust into the 
earth, and if one then imagines this long cylinder of ore set end-up 
on the surface like a pillar, an imposing column of magnetite almost 
a mile high and 80 feet or more in diameter would make a land- 
mark for the surrounding country. 
The walls. Both walls are Pochuck-Grenville, but in most places 
it is granitized. The footwall is the more highly granitized, for 
very coarse Pochuck granite appears at the surface in the little hill 
147 Unpublished and incomplete manuscript on the iron mines of New York, 
placed at the writer’s disposal by D. H. Newland. 
