SILICA. 



261 



Also the forms represented in Figures 134, 135, 136, 137, 138, and the twins 139 and 140. 

 These crystals are usually small. 



Fig. 134. 



Fig. 135. 



Fig. 136. 



Fig. 137. 



Fig. 138, 



Fig. 139. 



Fig. 140. 



Similar crystals are obtained in the slate near the paper mill, two miles west of Catskill ; 

 and during the process of excavations that were made for the railroad, large and beautiful 

 crystals were sometimes thrown out. 



Hehkimer County. Uncommonly beautiful specimens of rock crystal, perfectly transpa- 

 rent, have been found in various parts of this county, especially at Middleville, Fairfield, 

 Little-Falls, Salisbury and Newport. They are found sometimes in cavities in the calciferous 

 sandstone ; and at others, they lie loosely in the sand, probably produced by the disintegration 

 of the rock. Mr. Vanuxem has remarked, that there is probably no locality in the world 

 which produces more perfect or more beautiful quartz crystals than Middleville ; and with an 

 equal refractive power, they would rival the diamond. They are found of various sizes, and 

 variously grouped. Perfect crystals have seldom been found here of more than two or three 

 inches in length, while those of from three quarters of an inch to an inch are very abundant. 



