﻿52 NEW YORK STATE MUSEUM 



the scarcity of inclusions of other types, and the invariable utter 

 absence of limestone inclusions, notwithstanding the abundance 

 of limestone in the formation. Beyond doubt many of these in- 

 clusions represent limestone fragments altered in this fashion. In- 

 tense alteration, however, seems necessary, and that perhaps fur- 

 nishes a reason why the comparatively small fragments caught up 

 in the granite mass are so uniformly changed over, while at the 

 contacts the change is much less obvious, or common. In our dis- 

 trict here we have amphibolite inclusions everywhere in the granite 

 gneisses, but no instances of the conversion of pure limestone into 

 amphibolite along the contacts, similar to those in Ontario. There 

 are, however, one or two instances of similar alteration on a small 

 scale, in connection with narrow bands of limestone and small 

 granite intrusions. The most clearly shown of these is right in 

 the village of Theresa, at the road metal quarry near the lower 

 bridge. The rock quarried here is a contact phase of the limestone 

 cut through and through by granite dikes. The chief rock is green 

 in color and consists of pyroxene, titanite, feldspars and calcite, the 

 latter running as high as 50^ of the whole in the portions of the 

 rock most remote from the dikes. In contact with these, however, 

 the rock is black, consists chiefly of hornblende and feldspars, 

 though with a little remaining pyroxene and calcite, and has nearly 

 completed its transformation into amphibolite. Very near at hand 

 is the pure limestone band shown in plate 2, and there can be little 

 question but that the green rock of the quarry is an altered phase 

 of that, and no question at all but that the green rock is changed 

 into amphibolite by the granite. On a small scale then it is a 

 change identical with that described by Adams. 



Contact rocks of the Antwerp bathylith. In so far at least as 

 the portion of the Antwerp bathylith included within the mapped 

 district is concerned, the contact action of this granite is but slight, 

 and it would seem to have been quite deficient in mineralizing 

 agents, though as effective in the production of mixed rocks as the 

 other granites. The dikes and stocks of white granite run every- 

 where through the limestones without affecting them any, except 

 in trifling amount in a few localities, nor does near approach to the 

 margins of the bathylith produce any observable change in the 

 Grenville rocks. In the case of dikes of granite pegmatite however, 

 some contact action is the rule, coarsely micaceous rocks being the 

 usual ones produced. Locally the mica becomes very. coarse and in 

 well formed crystals, so much so that at one locality north of 

 Theresa an attempt was made to mine it commercially. The mica 



