SILICA. 



269 



Transparent and beautiful crystals, but which seldom exceed an inch in length, are still 

 found in considerable abundance on Diamond island, and at Diamond point, about a mile north 

 of the former. They are usually contained in cavities in the calciferous sandstone, and arc 

 associated with crystals of calcareous spar and pearl spar. Small particles of anthracite are 

 also occasionally found in these cavities, as is the case in Herkimer county. Perfect crystals 



Fig. 176. 



177. 



Fig. 178. 



Fii:. 179. 



Fia. ISO. 



Fig. 181. 



Fig 182. 



of large size are now very rare at these localities. Figs. 176, 177, 178 and 179 represent some 

 forms obtained at Diamond Point. Fig. 180 is from Diamond island. 



Westchester County. Drusy quartz occurs in geodes and cavities in hornstone, which 

 almost approaches calcedony, in the vicinity of New-Rochelle. It is associated with serpen- 

 tine and other magnesian minerals. 



Common quartz is found in masses of some size, in the vicinity of the village of Yonkcrs, 

 and also near West-Farms, where it is of a rose colour. 



At the marble quarry at Hastings, there are veins of calcedony, from | to ^ inch in width, 

 between the layers of tlie rock. The specimens are translucent, pale yellow and white. 



To the above I add. Fig. 

 181, the plagiedre oiUdiUy, 

 which, according to She- 

 pard, is found on the White 

 mountains in New-Hamp- 

 shire ; Fig. 182, the cmar- 

 gine of Haiiy, and .Fig. 183 

 from Shepard, both of which 

 occur at Quebec, Canada. 



Fig. 181. P on .(■ US° 

 42' ; r on a- 1G~ ' 5G' ; z on 

 X 125° W. 



Fig. 182. P on/ or ; on 

 fhU^ 40'. 



Fig. 183. P on o 1(30° 

 lo'; oono 125'^ 10' {Shr. 

 pard). 



