246 PSEUDOMORPHOUS MINERALS OF NEW YORK. 



mineral, and the causes which have operated to effect them, are 

 probably similar to those just noticed. 



Changes in Spinelle. 



There is in Orange county a mineral which has long been 

 known, and which has also passed under various names, as ke- 

 rolite pseudomorphous of spinelle, pseudolite, &c. These names 

 seem to have been employed to express the supposed chemical 

 constitution and the crystalline form. 



The crystals to which I refer are of a black color, and of an 

 octahedral form, exactly resembling those of spinelle. They are 

 imbedded in a gangue of soft, dark-colored serpentine. These 

 octahedi'ons can be scratched with a knife, and easily reduced to 

 a coarse powder ; but the powder, which is of a gray color, is 

 gi'itty, and with difficulty rendered impalpable. 



In conducting the analysis of this mineral, I found that a good 

 part of the powder operated on, resisted tsvo or three fusions with 

 carbonate of soda. This led me to suspect that it might contain 

 a portion of real spinelle, instead of its being, as I had supposed, 

 entirely made up of serpentine or some allied mineral. The 

 correctness of this view was confirmed by my subsequent exam- 

 inations. 



The composition of these crystals is nearly as follows, namely : 



SiHca, 19.07 



Alumina, 35.00 



Oxide of iron, . . . . . . . 9.97 



Magnesia, 28.58 



Water, 7.33 



If now we take about seventeen parts of the silica, fifteen of 

 magnesia, six of water, and two of oxide of iron, they will pro- 

 duce about forty per cent, of serpentine, and the remaining con- 

 stituents \vi]\ be nearly in the proportion in which they are 

 found, according to the most ti'ustworthy analyses, to occur in 

 spinelle. 



The peculiarity of this mineral, therefore, is to be referred to 

 the intrusion of the serpentine into the crystals of spinelle, a part 

 of which has been removed. And although the crystals are soft- 



