472 



NEW YORK STATE MUSEUM 



feature of the rock containing these constituents. Most of the 

 anorthosite of the quadrangle contains garnet and the black min- 

 erals in noticeable quantity, owing to its comparative nearness 

 to the border. 



Like the other Precambric rocks the anorthosite has been 

 much metamorphosed, being crushed or granulated and some- 

 what recrystallized. But owing to its original very coarse texture, 

 and to the fact that granulation mostly commences at the edges 

 of crystals and slowly works its way inward, the rock does not 

 appear so thoroughly metamorphosed as do the other rocks, none 

 of which approached it in original coarseness of grain. The crush- 

 ing which would have, completely granulated a more finely crys- 

 talline rock would only partially destroy the large labradorite 

 crystals, and uncrushed cores of large or medium size would 

 remain, even in the most excessively metamorphosed portions 

 of the rock. With increase in the amount of dark minerals present 

 the original grain of the rock seems to have been progressively 

 less coarse and such rock is generally more completely granulated, 

 with the uncrushed feldspar cores fewer in number and of smaller 

 dimensions. This is a more common rock within the quadrangle 

 than the coarser and purer variety. 



In some portions of the rock the feldspar crystals are more 

 numerous, are smaller and are all arranged with their long axes 

 parallel. This is a " flow structure " due to movement in the 

 mass during solidification, which has strung out the already formed 

 crystals into parallel arrangement. 



The granulated portion of the rock varies in appearance accord 

 ing to the fineness of the crushing. In the majority of instances 

 where not too finely granular, it has a grayish green to grayish 

 blue tinge weathering to brownish. In more severely mashed 

 portions the grain is very fine, gray to white is the color, the rock 

 is very dense and hard, and uncrushed cr3^stals much less frequent 

 and of smaller size. Sometimes locall}^, either near bodies of later 

 intrusives, or else in badly sheared portions of the rock, the feld- 

 spar has been largely altered to a dull, white or greenish white 

 material known as saussurite. This is quite different material 

 from the soft products of surface decay of the same mineral. Rock 

 of this sort makes up the rock point on the east bank of the Raquette 

 river h mile below the Raquette Falls landing. Similar material 

 occurs at various places in the woods. 



