322 



DESCRIPTIVE MINERALOGY. 



with iron pyrites, calcareous spar and dark brown hornblende.* I have diligently searched 

 for this mineral at the locality just mentioned, but have not succeeded in obtaining specimens 

 of it. The brown tourmaline is quite abundant in the white limestone, and it is possible that 

 it may have been mistaivcii for idocrase. 



This mineral has been found, by Dr. Emmons, in carbonate of lime at Long pond. 



Fig. 267. 



Jefferson County. On Muscolunge lake, in the town of Antwerp, 

 four miles norliiwest of O.xbow, tliis mineral occurs in light yellow 

 crystals, associated with crystallized mica, in white limestone. Some 

 of these crystals are similar to the pe.riocto.edre of Haiiy, Fig. 267, 

 M on d 135°; otiiers have modified terminations, but they are too 

 imperfect to be determined. 



Orange County. This mineral occurs in grains, crystals and crystalline masses, near the 

 village of Amity in the town of Warwick. The granular variety is probably that which was 

 analyzed by Dr. Thomson, and described by him as a new mineral under the name of 

 Xanthite. The colours are yellow and greenish yellow. Of the crystalline forms, there are 

 the perioctaedre of Haiiy (Fig. 207), and another highly modified crystal, too imperfect for 

 description. Some of the lateral planes are striated. The crystalline masses, according to 

 Dr. Horton, are not unfrcquenlly from six to ten inches in diameter. 



In regard to the xanthite, it may be remarked that there is still a difference of opinion. It 

 is usually placed under idocrase, with which the analysis of Dr. Thomson agrees very well. 

 It is as follows : 



Silica, 35 . 09 



Lime, 33.08 



Alumina, 17.43 



Peroxide of iron, 6. 37 



Protoxide of manganese, 2. 80 



Magnesia, 2.00 



Water, 1.68t 



On the other hand, Mr. Mather stales that it exhibits cleavages parallel to the faces of an 

 oblique rhomboidal prism. t The specific gravity is from 3.201 to 3.221. It is fusible by 

 the blowpipe, according to my trials, into a greenish bead. In my opinion, it is identical 

 with idocrase. Its associates are hornblende, apatite, etc. 



About half a mile south of the village of Amity, crystallized idocrase occurs of a greyish 

 and yellowish brown colour, in while limestone. There is another locality about a mile east 



• Shepard. American Journnl of Science. XVII. HO. 

 X American Journal of Science. XVlll. 359. 



t Thomson. Outlines of Mineralogy, Geology^ 4*-* 



