132 The Monoclinic Pyroxenes of New York State. 



tween is frequently filled with ealcite. The igneous rock also be- 

 comes more pyroxenic as the zone of contact is approached. 

 The most important of these contact localities are at Russell, 

 East Russel, Gouverneur, Pierrepont, Diana, Natural Bridge, 

 Rossie, Oxbow, Dekalb and Edwards. 



The small beds of ophicalcite of the eastern Adirondack re- 

 gion contain an abundance of pyroxene in grains and crj^stals, 

 which are either disseminated through the rock or else collected 

 with other minerals in the form of large bunches of silicates in 

 the limestone. An excellent illustration of these bunches of 

 silicates appears in a recent paper by Prof. J. F. Kemp. (See 

 Ref. 30.) 



In this same region the pyroxene not unfrequently occurs in 

 intimate association with the ore-bodies, either as well developed 

 crystals, or forming granular streaks between the ore bed and the 

 wall rock. 



The pre-cambrian rocks of the Highland region in southeastern 

 New York are composed of a series of gneissic and granitic 

 rocks, interbedded limestones and beds of iron ore, the whole in- 

 tersected by many dikes. The conditions of occurrence of 

 pyroxene in this region are therefore somewhat similar to those 

 found in the Adirondacks. While it occurs in grains and anhedra* 

 in many of the gneissic rocks and dikes its best development is 

 around the beds of magnetite. The most important localities are 

 at the O'Neil Mine, the Bradley Mine and the Sterling Mines. 

 Owing to the cessation of mining these localities are practically 

 exhausted. 



To the southwest of the Highland region the area around Mts. 

 Adam and Eve is of great importance, for the intrusion of the 

 granite into the limestone has given rise to a rich development of 

 contact minerals, pyroxene being among the best developed. 

 Most of the specimens have been found near Edenville. 



The gabbros and diorites of the Cortlandt Series, near Peeks- 

 kill, Westchester Co., contain an abundance of pyroxene, and the 

 same mineral has been formed as a result of contact metamor- 

 phism in the surrounding limestones (Ref. 61 and 63). The same 

 is true of the Rosetown extension of this area across the Hudson 

 River (Ref. 22). 



*L. V. Pirsson. Philadelphia Meeting Geol. Soc. Amer., Dec. 1895. 



