104 NEW YORK STATE MUSEUM 



unstriated feldspar abounds but is regarded as labradorite with 

 all appearance of twining destroyed by strain. 



The localized occurrence of this rock, together with its constant 

 peculiarities, disposes the writer to consider it as a separate intru- 

 sion, probably slightly later than the ordinary anorthosite in time. 

 The evidence for or against this view can be obtained only from 

 Essex county, if there. In Franklin county the only exposures 

 occur in the vicinity of Franklin Falls, the best being along the 

 river. Grenville limestones lie close at hand to the north and 

 east, and, as they are approached, the rock becomes rapidly more 

 basic, passing into a gabbro-gneiss of dark color, with a foliation 

 parallel to that of the succeeding Grenville rocks. 



On the west end of Catamount mount, 5 miles east of Franklin 

 Falls, in Clinton county, this Whiteface type is exposed, sur- 

 rounded on the north and east by the same gabbroic gneiss as at 

 Franklin Falls, this being followed by a red, granitic gneiss 

 toward the top of the mountain, with no contacts showing so far 

 as the writer has been able to discover. In this gabbro-gneiss 

 occasional augen of blue labradorite appear; in one place a con- 

 siderable face of rock like the Marcy type of anorthosite-gabbro 

 was seen, and near at hand, inclosed in a rotten brown gneiss, was 

 an unmistakable inclusion of ordinary anorthosite with numer- 

 ous blue labradorite augen, some of quite large size and iridescent. 

 The locality is very suggestive, but unfortunately the precise 

 nature of the inclosing rock is obscure on account of its decom- 

 posed condition. It is connected with, and seems to be a phase 

 of, the dark gabbro-gneiss rather than connected with the main 

 mass of the typical Whiteface anorthosite, and the question of the 

 relationship of this gabbro-gneiss is still an open one. From its 

 distribution around the edge of the Whiteface anorthosite it 

 would seem to represent merely a differentiation phase of that 

 rock, which would then be younger than the ordinary anorthosite. 

 It strongly resembles the gabbros whose consideration follows, 

 and may belong with them, in which case its apparent close re- 

 lationship with the Whiteface anorthosite may have a much 

 broader significance. Or the inclusion may not be an inclusion 



