36 ANNALS NEW YORK ACADEMY OF SCIENCES 



due to a reaction between the mica schist and the biotite norite, although 

 it is, of course, impossible to explain why the same conditions should have 

 given rise to the syenite to the west of it or the diorite to the east. That 

 the quartz in the rock of this little border patch is entirely adventitious 

 is quite improbable; its rather frequent occurrence in the rocks asso- 

 ciated with the emery would indicate that certain peculiar conditions 

 are requisite for its formation and that these conditions had been satis- 

 fied here. 



Augite Norite 



Augite norite is a basic and comparatively unimportant facies of the 

 biotite augite norite magma, having been found in two small patches on 

 the borders of the latter area and as streaks in pyroxenite on Montrose 

 Point. The smallest is at Montrose: the other, about half a mile east 

 of Pleasantside. Its position would thus seem to indicate that it is 

 merely a local segregation, derived by the loss of biotite. In the hand 

 specimen, it resembles hornblende norite most closely, since there is no 

 biotite. The rock is compact, dark gray and of medium grain. Under 

 the microscope, there is little of note. In the patch at Montrose, there 

 is a trace of biotite, while the augite and hypersthene are subequal in 

 amount. There is a remarkable development of apatite in this rock, 

 sharply crystallized in very large grains. In the rock from the other 

 patch, there is no biotite; the hypersthene is somewhat less in amount 

 than the augite, and both are characterized by such an abundance of 

 inclusions as renders them almost opaque. Bastite, chlorite, epidote 

 and kaolin are the well-developed alteration products. The streaks on 

 Montrose Point are similar to the last, except that the plagioclase is 

 more acid (approaching oligoclase) and the orthoclase abundant, being 

 about one-third of the feldspar. The hypersthene is light in color and 

 in pleochroism and is often in small elongated grains. The augite is in 

 larger crystals, with numerous black inclusions, and there are a few 

 grains of brown hornblende. 



Hornblende Norite 



Hornblende norite is the third important member of the norite group. 

 The bulk of it occurs in the large area to the southwest of Pleasantside ; 

 the rest in a small patch half a mile to the southeast. The former is 

 entirely surrounded by norites, while the latter is on the edge of the 

 norite district. 



The rock in the hand specimen can usually be identified as a norite bv 

 the pink or (when altered) brownish color of the feldspar. The absence 



