248 psEUDOMORPnors minerals of new york. 



eii2^n matter, bnt still having tlio form and cleavage of pyroxene. 

 This author quotes three analyses by Rose, one of which is 

 as follows, namely : 



Silica, 60.65 



Lime, 4.97 



Magnesia, 25.20 



Protoxide of iron, 4.18 



Oxide of manganese, 0.78 



Water, 4.38 



According to calculation, this contains pyroxene, 37.40, stea- 

 tite, 62.30, hygi-ometric water, 0.40. 



The localities of this altered mineral are so numerous in 

 the counties of St. Lawrence, Jefferson, and Lewds, and they are 

 of such considerable extent, that the cause which operated to 

 produce the change must have been a general as well as a pow- 

 erful one. An examination of the beds of white limestone in 

 which the altered masses are found, sufficiently attests the agency 

 of heat. Nodules and semi-crystalline forms of serpentine every 

 where occur, together with hexahedral scales of gi'aphite. And 

 the crystals of phosphate of lime, quartz, scapoUte, and of other 

 minerals, constantly exhibit that rounded form, which we at 

 once ascribe to fusion at the moment of, or subsequently to, 

 their formation. Now the heat necessary for the fusion of quartz 

 would easUy effect the liquefaction of pyi-oxene. And if in this 

 lava-state the materials of serpentine were injected into this 

 mineral, it would produce a change similar to that which is now 

 observed in the steatitic pyroxene. 



Before this explanation can be received, however, an impor- 

 tant qviestion is to be decided. It is this : whether the presence 

 of one mineral substance, especially if it be not peculiarly sus- 

 ceptible of crystallization, changes the crystalline form of another 

 mineral ? In some cases I am aware that very small proportions 

 of one salt will change the crystalline form of another salt; as 

 where sulphate of iron crystallizing in a solution of alum, takes 

 the octahedral form of the alum, although the crystals contain 

 scarcely a trace of this salt. I am also aware, that certain bodies, 

 when they exist together in solution, may, in a striking manner, 



