38 MINERALOGY AND LITHOLOGY. 



copper pyrites. At Orford, where the copper ores are decomposed at 

 the surface, some green carbonate of copper has been formed, and also 

 some black oxide. As there observed, it is an earthy, black substance, 

 easily reduced on charcoal with the blow-pipe to metallic copper. It is a 

 mineral of little importance to us. 



24. Corundum [AI2 O3]. 



When this substance is impure, from the presence of oxide of iron, it 

 is called emery. It is stated, in the old lists of mineral localities, that 

 emery has been found at Lancaster and Lyman. The present survey 

 has not detected it, and is not able to verify the statement. 



25. Hematite [Fe^ O3]. 



There are large deposits of this oxide of iron in some parts of the 

 state, and in some places the effort has been made to extract it. Of the 

 most mineralogical interest, the ore, as it occurs at Piermont, may be 

 mentioned. There it is found in a micaceous form, made of a mass of 

 the brightest scales. This ore has been analyzed by Jackson, with the 

 following result : 



Iron sesquioxide, . . . . . . . . . . 93.5 



Titanic acid, 3.8 



Impurities, ........... 2.7 



A part of the iron ore in the beds at Bartlett and Jackson is hematite. 

 Franconia, Lisbon, and Rindge are other localities; while in insignificant 

 amounts it is found in many other places, and, as a microscopic ingre- 

 dient, it is scattered through all our bedded rocks. 



It is most natural to find this oxide of iron so widely spread in our old 

 crystalline rocks; for, as has been often shown, beds of iron ore are in 

 general accumulated by the agency of water, which brings together de- 

 posits of the hydrous iron sesquioxide, as can be seen in certain boggy 

 places where similar deposits are being formed to-day ; and, when beds 

 have been subjected to such heat as we may suppose has operated in the 

 crystallization of our granitic rocks, the water has been driven out, trans- 

 forming them into hematite ; when, at the same time, some reducing 



