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 mistaken for idocrase. 
This mineral has been found, by Dr. Emmons, in carbonate of lime at Long pond. 
Fig. 2G7. 
Jefferson County. On Muscolunge lake, in the town of Antwerp, 
four miles northwest of Oxbow, this mineral occurs in light yellow 
crystals, associated with crystallized mica, in white limestone. Some 
of these crystals are similar to th e perioctaedre of Hauy, Fig. 267, 
M on cl 135°; others 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. 267), 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 unfrcquently 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,..... 1.68f 
On the other hand, Mr. Mather states that it exhibits cleavages parallel to the faces of an 
oblique rhomboidal prism.f 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 white limestone. There is another locality about a mile east 
* Shepard. American Journal of Science. XVII. 140. 
% American Journal of Science. XVllf. 359. 
f Thomson. Outlines of Mineralogy, Geology, Sfc. 
