COPPER ORES. 291 



Siberia, Cornwall, and Brazil, are noted for the copper 

 they have produced. A mass supposed to be from Bahia, 

 now at Lisbon, weighs 2616 pounds. The vicinity of lake 

 Superior is* one of the most extraordinary regions in the 

 world for its native copper, where it occurs mostly in ver- 

 tical seams in trap, and also in the enclosing sandstone. A 

 mass weighing 3704 lbs. has been taken from thence to Wash- 

 ington city : it is the same that was figured by Schoolcraf* 

 in the American Journal of Science, volume iii, p. 201 

 Masses from 1000 to 3700 pounds, from this region, hav 

 been exposed on the wharves of Boston, Mass. This i 

 small compared with other pieces which have since beei 

 laid open. One large mass was quarried out in the " Cliff 

 mine," whose weight has been estimated at 200 ions. Il was 

 40 feet long, 6 feet deep, and averaged 6 inches in thickness. 

 This copper contains intimately mixed with it about T 3 7 per 

 cent, of silver. Besides this, perfectly pure silver, in strings, 

 masses, and grains, is often disseminated through the cop- 

 per, and some masses, when polished, appear sprinkled with 

 large white spots of silver, resembling, as Dr. Jackson ob 

 serves, a porphyry with its feldspar crystals. Crystal* 

 of native copper are also found penetrating masses of preh 

 nite, and analcime, in the trap rock. 



This mixture of copper and silver cannot be imitated by 

 art, as the two metals form an alloy when melted together. 

 It is probable that the separation, in the rocks, is due to the 

 cooling from fusion being so extremely gradual as to allow 

 the two metals to solidify separately, at their respective 

 temperatures of solidification — the trap being an igneous 

 rock, and ages often elapsing, as is well known, during the 

 cooling of a bed of lava, covered from the air. 



Small specimens of native copper have been found in the 

 states of New Jersey, Connecticut, and Massachusetts, where 

 the same formation occurs. One mass from near Somerville 

 weighs 78 pounds, and is said originally to have weighed 

 128 pounds. Near New Haven, Conn., a mass of 90 pounds 

 was formerly found. Near Brunswick, N. J., a vein or sheet 

 of copper, from a sixteenth to an eighth of an inch thick, 

 has been observed and traced along for several rods. 



Where has rmuve copper been found in the United States ? Wha 

 is said of its associations with silver ? What explanation :e given ot 

 this mixture of copper and silver ? 



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