OHES OF COPPER. 13} 



Native Copper. 



Isometric. In octahedrons ; no cleavage apparent. Often 

 in plates or masses, or arborescent and filiform shapes. 



Color copper-red. Ductile and malleable. H. =2*5-3. 

 GL=8;84. 



xsative copper often contains a little silver disseminated 

 throughout it. Before the blowpipe it fuses readily, and on 

 cooling it is covered with a black ox} T d. Dissolves in nitric 

 acid, and produces a deep azure-blue solution on the addition 

 of ammonia. 



Obs. Native copper accompanies the ores of copper, and 

 usually occurs in the vicinity of dikes of igneous rocks. 



Siberia, Cornwall, and Brazil are noted for the native cop- 

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

 now at Lisbon, weighs 2,016 pounds. South of Lake Supe- 

 rior about Portage Lake on Keweenaw Point, and also, less 

 abundantly, on the Ontanagon Eiver, and at some other 

 points in that region, native copper occurs mostly in veins 

 in trap, and also in the enclosing sandstone. A mass 

 weighing 3,704 lbs. has been taken from thence to Wash- 

 ington City ; it is the same that was figured by School- 

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

 201. One large mass was quarried out in the " Cliff Mine," 

 whose weight has been estimated at 200 tons. It was 40 

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

 This copper contains, intimately mixed with it, about T \ 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. Crystals of 

 native copper are also found penetrating masses of prehnite 

 and analcite 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 separa- 

 tion 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. Native copper occurs sparingly in St. Ignace 

 and Michipicoton Islands, Lake Superior. 



