278 PHYSIOGRAPHY. 



Idocrase. 



3. Some of the varieties of Idocrase occur in serpentine, others in 

 veins in gneiss and limestone, and in ejected volcanic masses. It is 

 commonly associated with Garnet, Pyroxene, Mica and Hornblende. 



4. The imbedded crystals of the form unibinaire, have been found on 

 the banks of the Wilui river, and Lake Baikal in Siberia ; the implanted, 

 complicated crystals occur at Monte Somma, among the fragments eject- 

 ed by Vesuvius, and have been originally formed in those cavities of the 

 rock in which they are found. At Hasta, near Eger in Bohemia, it oc- 

 curs in long, reddish-brown, deeply striated forms, and in columnar 

 masses; in similar circumstances inFinland. In beds in limestone, it occurs 

 at Orawitza in the Bannat of Temeswar, and at Mount Monzoni near Fassa 

 in Tyrol ; also near Christiania in Norway, and in magnificent crystals 

 of a light green color, in the valley of Brozzo, and at other places in 

 Piedmont. A variety from Tellemarken in Norway, of a blue color, and 

 containing copper, has been called Cyprine. 



The most interesting specimens of Idocrase which the U. S. has hith- 

 erto afforded, were discovered at Worcester, (Mass.) in aquartzoserock, 

 in which it formed seams and veins, accompanied by Pyroxene and Gar- 

 net. The variety is precisely similar to that from near Eger in Bohe- 

 mia. Another locality is at Amity, (N.Y.) where it occurs both granu- 

 lar and in crystals, (sometimes an inch in diameter,) disseminated through 

 limestone with Pyroxene and Hornblende. The granular variety was 

 supposed by Dr. THOMSON to constitute a new species, to which he 

 g.ive the name of Xanthite. The handsome brown crystals accompany- 

 ing Corundum at Newton, (N. J.) have been erroneously referred to 

 this species : they belong to Tourmaline. 



IGLOITE. (See Jlrrogonite.') 

 ILMENITE. (See Crichtonite.) 

 ILVAITE. (See Yenite.) 

 INDIANITE. 



Massive ; composition granular to impalpable. It yields to 

 cleavage, according to BROOKE, in two directions, inclined to each 

 other under angles of 93 15' and 84 45'. 



Lustre vitreous. Color greyish-white, with a tinge of rose- 

 red. Translucent. 



