ORES OF COPPER. Sa 
Native Copper. 
Isometric. In octahedrons; no cleavage apparent. Often 
in plates or masses, or ar borescent and filiform shapes. 
is oe ee -red. Ductile and malleable. H.=2-5-3. 
eae copper often contains a little silver disseminated 
throughout it. Before the blowpipe it fuses readily, and on 
cooling it is covered with a black oxyd. 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 2,616 pounds. South of Lake Supe- 
rior about Portage Lake on Keweenaw Point, and also, less 
abundantly, on the Ontanagon River, 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 Ibs. 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 ii. mt 
201. One large mass was quarried out in the * Cliff Mine,” 
whose weight has been estimated at 200 tons. It was 40 
feet long, 6 feet deep, and averaged 6 inches in UMS. 
This copper contains, intimately mixed with it, about 5%, per 
cent. of silver. Besides this, perfectly pure sily er, In see: 
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. 
