PSEUDOMORPHOUS MINERALS OF NEW YORK. 251 



southern part of New Yorlv. Among these I may here mention 

 the fact that in the gneiss which abuts upon this dolomite there 

 are crystals of epidote, stilbite, apophyllite, mesotype, and other 

 minerals quite peculiar to rocks of igneous origin. I have also 

 found analcime in well defined leucite crystals, together with 

 a gi-eat abundance of rounded trapezoidal crystals of garnet in 

 the gneiss at Yonkers, in Westchester county, which is also asso- 

 ciated with the dolomitic deposit. 



Changes in the Ores of Iron. 



It not unfrequently happens in the northern part of New York, 

 that beds or parts of beds or veins are alternately made up of the 

 magnetic uon ore and the specular ore. This is particularly ob- 

 servable in the Arnold mine in Clinton county, where the ore in 

 one of the veins, although it has the structm-e and all the exter- 

 nal characters of the magnetic oxide, gives a red pow^der, and 

 upon analysis is found to be the peroxide of iron. In the Saxe 

 mine, at Crown Point, the ore, which seems to have been origi- 

 nally magnetic, has been changed to the peroxide, and indeed in 

 this case the structure is fibrous, exactly resembling that of the 

 Limonite of mineralogists. INIore partial changes of a similar 

 kind occm- in many of the deposits of iron ore in other parts of 

 Essex county, as at the Everest and Green mine, where the mag- 

 netic passes into the specular or red ore in various parts of the 

 vein or bed. 



Changes similar to the preceding have been noticed by Hai- 

 dinger. In the papers already referred to, he describes " the octa- 

 hedral crystals from Brazil, often of considerable magnitude, and 

 of a particular ore of iron. They afford a red streak, and seem 

 to contradict the characteristic of Mohs, namely, that it should 

 have a black streak. On a more close inspection, however, the 

 octahedral masses are found to be composed of a gi-eat number 

 of small crystals resembling those of the rhombohedral iron ore, 

 a species, one of whose characters is in fact the red streak ob- 

 served. A specimen from Liberia given to Mr. Allan by Sir A. 

 Crichton, presents the same change, excepting that in this speci- 



