338 



DESCRIPTIVE MINERALOGY. 



Rockland County. Minute crystals of feldspar are found imbedded in the variegated lime- 

 stone at Montaigne's quarry, two and a half miles northwest of Grassy point. This is also 

 one of the minerals imbedded in the greenstone near Piermont. 



St. Lawrence County. The most interesting localities of feldspar hitherto found in the 

 State of New-York, occur in this county. 



A mile southwest of the village of Gouverneur, large crystals of feldspar have been ob- 

 tained. They are white, and are highly modified. The associates are quartz, green pyroxene, 

 and babingtonite. 



Eight miles from Potsdam on the road to Pierrepont, feldspar is said to have been found in 

 crystals twelve inches in diameter.* And according to the same gentleman, quoted below, 

 there is a hill of red feldspar about a mile beyond Allen's mill, on the Oswegatchie. 



There is a fine locality of crystallized feldspar in the town of Rossie, two miles north of 

 the village of Oxbow, where it is associated with pargasite, pyroxene, sphene and apatite. 

 The crystals are white and bluish-white, and vary in size from a quarter of an inch to an inch 

 in diameter. 



Among the forms obtained here, are those represented in Figs. 307, 308 and 310; and also 

 in Fig. 313, the quadrihexagonal of Haiiy, with the faces M and P enlarged ; Fig. 314 ; and 

 Fig. 315, a modification of the decidtiodecimal of Haiiy. M on n 135° ; M on 5 116° 20'; 

 M on y 90° ; M or T on z 150° ; F on y 99° 29' ; F on s 124° 10'. 



Fig. 313. 



Fig. 314. 



Fig. 315. 



Near De Long's Mill, in the town of Hammond, crystallized feldspar is found associated 

 with apatite and zircon, in white limestone. The crystals are yellowish white or dark brown, 

 and they are often bent, and have the edges rounded as if they had been fused. There have 

 been found at this locality the sexdecimal (Fig. 311), and the synoptique of Haiiy, Fig. 316 ; 

 also Fig. 317, and the twin crystals represented in Figs. 318 and 319, in which the face of 

 composition is parallel, and the axis of revolution perpendicular to M. M on n 135° ; q on 

 X 164° 40'. 



* Finch. American Journal of Sciaice. XIX. 220. 



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