MAGNETITE IRON DEPOSITS OF SOUTHEASTERN NEW YORK OI 
to the folded condition of the Grenville in the Adirondacks, because 
he thought insufficient evidence had been accumulated to prove the 
existence of such structures. Thus he says: “none of the published 
Adirondack maps or available data afford any reasons to believe 
that the Grenville strata were ever profoundly folded or com- 
pressed.” (p. 592) In summarizing, he adds “ there is no 
known evidence within the Adirondack region that the Grenville 
strata have ever been highly folded. . . .” (p. 596) He accounts 
for the foliation as follows: “the Grenville foliation was developed 
during the crystallization of essentially horizontal strata under heavy 
load of overlying material.” (p. 597) Whatever the character of the 
structure may be in the Adirondacks and in the Highlands of New 
Jersey, there seems to be sufficient structural evidence in the High- 
lands of southeastern New York to show that: 
a The Grenville strata were intensely metamorphosed and strongly 
folded before the invasion of the igneous masses which so pro- 
foundly modified them, as previously stated; and 
b No folding of any magnitude has affected either the invaded 
complex or the ore bodies, since the ores were deposited. 
c Whatever the structures shown by the ore bodies, they were 
inherited from former structures 1n the rock replaced, in most cases. 
Where folds are simulated, as in the Forest of Dean mine (see 
figure 3), these are judged to represent structures inherited from 
the Pochuck-Grenville, or the Grenville, and its modifications. 
The proof of the first statement lies in the following field relations: 
1 Where the Grenville still exists in unmixed exposures folded 
structures are in most cases visible. 
2 Xenolithic blocks of Grenville schists swamped in granite, 
exhibit folded structures, but the inclosing granite shows no evi- 
dence of ever having been folded. 
3 The existence of roof-pendants of Grenville schist isolated from 
one another, all maintaining the same regional strike and the same 
steep dip; they are highly metamorphosed coarse micaceous schists, 
obviously parts of a large mass having the same characteristics in 
common with the remnants left, and whose structure was antecedent 
to the invasion of the granite. 
4 Changes in dip and strike in the modified Pochuck-Grenville 
in the vicinity of some of the ore bodies; indicating pitching folded 
structures, inherited. Notably, on the west, south and east sides of 
Sterling lake (see fig. 6), in the vicinity of the Scott group of mines 
“+. Q), in the vicinity of the Mahopac mine, and elsewhere. 
