ALUMINA. 



359 



Fti- 3G3. 



I-'is. 3C1. 



St. Lawrence County. Near the village of Gou- 

 vcnicur, crj'stals of tourmaline have been found, vary- 

 ing from one inch to several inches in length, and 

 from one to four inches in diameter. The colours 

 are light reddish brown, cinnamon and dark brown, 

 and they arc associated with apatite, scapolite, mica, 

 etc. in white limestone. The nonodiiodecimah of 

 Haiiy, Fig. 363, and the form Fig. 3G1, have been 

 found at this locality ; but it is difficult to obtain per- 

 fect crystals. P on o 141° 40'; P on n 156° 43' ; I 

 on 135^ 44' ; o on o 103'^ 20' {Hai'iy). 

 At Kichville, in the town of Dekalb, brown tourmaline, in perfect crystals, associated with 



tremolite, occurs in the soft and tough pyroxene and white limestone. The crystals are very 



brittle ; and this, together with the peculiar toughness of the gangue, renders it exceedingly 



difficult to obtain perfect crystals. 



Eight miles from Potsdam, on the road to Pierrcponl, tourmaline is said to have been found 



in crystals three inches in diameter.* 



Saratoga County. One of the most interesting localities of tourmaline in this State, is in 

 the town of Greenfield, about a mile north of Saratoga-Springs. The mineral is of a jet black 

 colour, often having the sides and terminations highly finished. The crystals are usually 

 small, and are associated with garnet, chrysoberyl, feldspar, apatite and mica, in quartz or 

 a very coarse granite which forms a vein in gneiss. The following forms have been observed 

 at this locality, viz : Fig. 362 ; Fig. 365, the isogone of Haiiy ; Fig. 366, the same with 

 the additional plane / ; Fig. 367, tredccimalc of Ilauy ; Fig. 368, a modification of the pre- 

 ceding ; 



Fig. 365. 



Fig. 366. 



Fig. 3G7. 



Fig. 368. 



f^ 



*1. Fincli. Americayt Journal of Scmicf. XIX. 220. 



