336 



DESCRIPTIVE MINERALOGY. 



Fig. 306. resemble the prismatique of Haiiy. Fig. 306. M on Z 120° ; P on Z 



111° 40'. 



The variety necronite, in translucent crystals, usually imperfect, is 

 also found at this locality. It is very fetid when rubbed briskly, or 

 wrhen struck .with a hammer. 



About five miles north of Ticonderoga, in Crown-Point, good clea- 

 vages of red feldspar have been obtained. The associates are quartz 

 and magnetic iron ore. 



In Newcomb, it occurs, according to Dr. Emmons, of a green colour. 

 To these localities several others might be added, as there is scarcely 

 a mine of magnetic iron ore at which feldspar is not found, either as 

 an associate of the ore, or forming a part of the rock in the immediate vicinity. But I have 

 never observed it in these situations exhibiting regular crystalline forms, although it is often 

 susceptible of cleavage. 



Herkimer County. Fine cleavages of feldspar of pale flesh-colour, may be obtained on 

 the banks of the canal in the immediate vicinity of Little-Falls. Other common varieties also 

 occur in the gneiss near this village. 



Jefferson County. A valuable bed of whitish feldspar occurs on High island, in the St. 

 Lawrence, nearly opposite to Alexandria. It is said to be suitable for the manufacture of 

 porcelain.* 



Lewis County. Near Natural bridge, feldspar, 

 both crystallized and massive, is found in white 

 limestone. The crystals have a white and yel- 

 lowish white colour, and are from a quarter to 

 three-quarters of an inch in length. They are 

 associated with pyroxene and hornblende. Among 

 the forms are the prismatique of Haiiy (Fig. 306) ; 

 and also the modifications represented in Figs. 

 307 and 308. M on I 120° ; P on Mll° 40'; P 

 on s 124° lO'; P on y 99° 29' {Haiiy). 

 The massive variety often has a bluish colour, and is associated with the black pyroxene, 

 scapolite and sphene, for which this locality is so much celebrated. 



New-York County. At Thomson's quarry, near 196th-street (Kingsbridge), necronite or 



fetid feldspar is found in the white limestone. It is bluish white, and is very fetid when struck. 



At Harlem (30th-street and 9th avenue), small crystals of feldspar, of the primary form, 



are found in the fissures of gneiss. There is also a six-sided prism formed by the truncation 



Fig. 307. 



Fig. 308. 



Emmons. New-York Geological Reports, 1837. 



