ECONOMICAL MINERALOGY. 



Fig. 4. 



Fig. 5. 



Warwick, Orange County. 



O'Niel Miue, Orange County. 

 (Very rare.) 



Cleavage parallel with the primary form. In some cases, as in the specimens from the Rich 

 Iron Mine in Orange county, easily obtained ; in others, entirely obliterated by the conchoidal 

 or uneven fracture. 



Lustre metallic, but sometimes imperfect ; opaque, brittle. Hardness 5.5 to 6 .5. Specific 

 gravity 4.74 to 5.09 (Beudant) ; 5.092 (Thomson) ; 4.20 to 5.20 (Cleaveland) ; 4.729 to 

 5.019 by my own trials on massive varieties from this State. 



Not altered by the blowpipe per se. But when highly heated, it assumes a brown colour, 

 and loses its power over the magnetic needle. With borax, in the oxidizing flame, it fuses 

 into a dull red glass, which becomes clear on cooling, and often assumes a yellow tint. In the 

 reducing flame, it becomes bottle green. 



Insoluble in nitric acid ; usually soluble in hot concentrated muriatic acid, but for this pur- 

 pose the mineral should be reduced to a very fine powder. Sometimes, however, the presence 

 of foreign matters renders it necessary to calcine the ore with carbonate of soda or potash be- 

 fore its solution can be effected. 



Distinctive characters. The black colour of its powder, and its strong action upon the 

 magnet, will usually serve to distinguish this species from the specular oxide of iron, which 

 it often resembles. 



Composition. This mineral was formerly supposed to be a pure protoxide of iron. It was 

 first proved by Berzelius that it contains both the protoxide and the peroxide of iron. Accord- 

 ing to that celebrated chemist, tlie proportions are 31 protoxide to 69 peroxide ; but these pro- 

 portions are subject to great variations. 



The value and importance of this ore vrill be properly appreciated by the single remark, 

 that the Swedes iron, so justly esteemed in the arts, is produced entirely from it. 



Geological situation. The magnetic oxide of iron is most generally found in beds or 



