MAGNETITE IRON DEPOSITS OF SOUTHEASTERN NEW YORK 79 
not far from correct. Its extension northerly has not been deter- 
mined, but there are surface evidences of its emergence at the south 
end of the lake. 
The slip-zone destroys the rolls, but does not apparently offset 
the ore so far as can be determined from the present stage of 
development work. The extension of the main slope has carried it 
through this zone on the lower levels of the mine, and massive ore 
was encountered on the eastern edge of the mixed rock-and-ore 
zone, as well as a renewal of the rolls, the axes of which at this 
point strike about north 78° east (estimated by the writer) as con- 
trasted with an almost due east-west strike in other portions of the 
mine, and a strike of north 78° west at the base of the hill just 
south of the lake (see fig. 6). 
The character of the rock in the slip-zone suggests that this zone 
may have been a channel of distribution for the intensely active, 
magmatic end-stage mineralizing aqueo-igneous solutions judged to 
have been responsible for the deposition of the magnetie. Coarse 
pegmatite, and large crystals of pyroxene, feldspar, garnet, epidote, 
quartz, occasionally tourmaline, and other characteristic minerals 
usually found in pegmatites, are derived from this zone, especially in 
shrinkage cavities or vug's, all intermingled with rock of the quality 
of Pochuck-Grenville the whole mixed with sufficient disseminated 
magnetite to make concentration a possibility. 
A critical study of some of the material shows that it has been 
fractured and faulted, but that it is now tightly healed by the 
products of magmatic end-stage emanations; that is, by epidote, 
soda-feldspars, carbonate and the like. It is probable that the period 
of deformation was very closely related to, and slightly overlapped 
the healing period, for fractures in the feldspar are in places healed 
with feldspar; and micro-crush zones in epidote crystals exhibit 
crushed epidote healed with epidote itself, so that a sort of selective 
action obtained during the process. 
It would appear, therefore, that whatever deformation occurred 
must have been an accompaniment of the invasion of the Pochuck 
magma; that the “slip-zone” is a Precambrian crush-zone, pro- 
duced slightly later than the cross-corrugations called “the rolls,” 
since these are destroyed within the zone, but a product of the same 
set of forces. And possibly serving as a channel for the magmatic 
end-stage products, related also to the same general period. (See 
plate 9, figures 2 and 4.) 
The ore. The ore in the Lake mine is in general a compact, fine- 
