24 NEW YORK STATE MUSEUM 



I 



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minerals, including garnet. A few examples follow. On the 

 southern side of Hawk island in Lake Placid, big ledges show 

 typical nearly white anorthosite and a gray anorthosite with 20 to 

 25 per cent of dark minerals, these two facies not being sharply 

 separated. Along the river two-thirds of a mile west-northwest 

 of Owen pond there are big ledges of Whiteface anorthosite with 

 zones of very gneissoid, dark, gabbroic anorthosite. On the moun- 

 tain spur two-thirds of a mile southeast of Morgan pond there is 

 locally developed in the Whiteface anorthosite a strongly gneissoid 

 facies. In the little area of mixed gneisses one-half of a mile east 

 of Keene village the Whiteface anorthosite shows a local develop- 

 ment rich in black minerals and garnet. By the river three-fifths 

 of a mile west of Owen pond a single outcrop exhibits quite typical 

 Whiteface anorthosite and a very gabbroic facies (no. 34 of 

 table i) in fairly sharp contact but without one cutting the other. 

 Local variations of the sort here described are believed to have 

 been produced as a result of differential fiowage under moderate 

 pressure in the cooling and differentiating anorthosite magma, this 

 matter being rather fully considered beyond. 



Certain exceptional types of very limited extent deserve men- 

 tion. One of these forms the walls of The Flume through which 

 flows the West Branch Ausable river. It is medium to moderately 

 coarse grained, consists very largely of pink labradorite together 

 with 2 to 15 per cent of hornblende and pyroxene scattered through 

 the mass, and is at times slightly gneissoid. This is no. 17 of 

 table I. It contains no large blue labradorite crystals. Some small 

 drawnout or lenslike inclusions of Grenville pyroxene gneiss occur, 

 a careful study of these in the field having led to the suggestion 

 that most of the much smaller (one-fourth to one-half of an inch) 

 lenslike masses which make up 5 to 15 per cent of considerable 

 portions of the rock are really very small fragments of Grenville 

 gneiss which were caught up in the intruding magma and roughly 

 arranged parallel to the magmatic lines of fiowage. 



The only other similar pink anorthosite found, occurs in the 

 small area on the mountain side i mile east-southeast of Owen 

 pond. This rock never shows over 2 per cent of dark minerals, 

 and it contains no inclusions of Grenville. 



Another exceptional type is medium grained and almost pure 

 white, with about i per cent of green pyroxene and very few 

 scattering grains of ilmenite and titanite. In thin section it shows 

 fully 24 per cent of colorless monoclinic pyroxene with good 

 cleavages. This is no. 18 of table i. It is finely exposed in bare 



