52 NEW YORK STATE MUSEUM 
operations of the processes outlined above. The many different 
types of banded, injected gneisses encountered are due in large part 
to the originally variable habit and composition of the previously 
metamorphosed Grenville sediments subjected to these processes. 
The term “ Modified Pochuck-Grenville”’ includes, therefore, (a) 
pegmatized Pochuck-Grenville, (b) epidotized Pochuck-Grenville, 
(c) granitized Pochuck-Grenville, and all banded and injection 
modifications in general. (See plate 4, and plate 6, figure 4.) 
DAE GRANIDES 
Pochuck Granite. Almost invariably extremely coarse, white 
or light-colored, highly quartzitic and more or less feldspathic rocks 
are associated with the ore bodies, not infrequently forming parts of 
the walls, and commonly outcropping in the immediate vicinity of, 
and lying along the trend of the ore. Such, for example, as the 
light-colored, coarse granite adjacent to the footwall of the Forest 
of Dean mine, forming a part of the little hill just west of the 
shaft house; and the same type of granite in the immediate vicinities 
of the Clove, O’Neill, Bering, Denny, Lake and other mines, usually 
found close to or along the walls of the open cuts, or the walls of 
the ore bodies, or in their vicinity. 
Farther removed from the immediate vicinity of the magnetite 
bodies the same type of granite may be observed, always much more 
involved, however, with the Pochuck-Grenville, and more exten- 
sively distributed than has commonly been supposed. 
The writer first tried to correlate these coarse granites with the 
Canada Hill granite of Berkey and Rice,”® but a critical examination 
of their modes of occurrence, distribution and petrographic habit, 
and a comparison of them with the established types of the Canada 
Hill, seemed to prove the nonrelationship of the two. 
Because of the constant and intimate association of these coarse 
granites in their purer form with the ore bodies, and because of — 
certain peculiar petrographic characters, it is judged that they are 
genetically related to the magnetite, and are a product of the ulti- 
mate extreme end-phase selective crystallization (elimination resi- 
duum) of the Pochuck magma. That is, they are the ultimate 
product, in part, of extreme differentiation, representing the highly 
quartzitic, more or less feldspathic, last remaining mother liquor. It 
is conceivable, also, that some of the quartz might have been derived 
—— 
99 Berkey, C. P., & Rice, Marion. Geology of the West Point Quadrangle. 
N. Y¥. State Mus. Bul. 225-226. 
