414 On Sulphurets of Copper from the Canton (Ga.) Mine. 
And in 1836, Mr. Fox submitted to the British Association an 
experiment showing that yellow copper (pyrites), in a dilute 
solution of sulphate of copper, under the influence of a w 
galvanic current, undergoes a change by which “a black and 
somewhat friable crust” of sulphuret of copper was formed, and 
native copper deposited in “brilliant crystals” on the sulphuret. 
That all the conditions for such decomposition and recomposi- 
tion occur at the Canton mine, the above description will amply 
testify, and that such changes are in actual progress is proved by 
a specimen of copper pyrites in my possession, which is com- 
pletely blackened by a very thin coat of the sulphuret, while 
mispickel and pyrites in immediate contact still retain their color 
This power thus exerted in the formation of Harris- 
ite and Cantonite is probably as active in pseudomorphic changes 
as in any other. The question then arises, Can they be pseudo- 
mo n my first examination of these crystals in August, 
1855, I considered them copper-glance in forms of galena, and 
their porosity} well Ree taking their specific gravity by 
the escape of air bubbles, strengthened that opinion. Subsequent 
examination of the locality and a greater variety of specimens, 
has entirely removed that impression. e occurrence of both 
minerals crystallized in connexion with erubescite renders It 
highly improbable that they replaced galena in that connection. 
Galena, with a cubical fracture (if it does in any form) does not 
occur in contact with the sulphurets. Nor are they found occu- 
pying the normal position of the galena, in strings along the wall. 
his negative evidence, with some minor considerations, but 
especially the character of the crystals, the lustrous cleavage 
planes of which, with their sharp and well-defined angles, dis- 
agreeing so decidedly with pseudomorphic characters, renders 
some positive evidence necessary to prove them pseudomorphs. 
Nor can Cantonite be Covelline in form of Harrisite, since the 
latter is never found among cubic pyrites, where the former 18 
In conclusion, I infer from the results of this investigation that 
copper glance is dimorphous, Harrisite being its monometric 
form. Also that Covelline is dimorphous, Cantonite being 18 
monometric form. The cause of this latter dimorphism will 
probably be found in the fact that the monometrie crystals are 
formed by aqueous, and the hexagonal (covelline) by igneous 
agency. Again, that Harrisite and Cantonite will not be found 
at great depths, but only within the range of decomposition. Oa 
7 Seer bynes, then, and the argentiferous galena, will ret 
Phe 
get? 
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