COPPER. This metal was known at a very remote period ; and in the early ages of the world, before iron was in use, copper was the chief ingredient in do mestic utensils and instruments of war. It is an abundant metal, and is found native, and in many ores ; of these the most im portant are the varieties of pyrites, which are sulphurets of copper and iron. There are 19 principal ores of copper, and seve ral subvarieties. There are no rules by which copper ores may be known exter nally, but after fusion with nitre, water of ammona receives a deep blue tint from any cupreous ore. The ores are na tive copper, sulphurets, oxides, silicates, carbonates, sulphates, phosphates, do rides, and arsenates. Native copper is found abundantly on the shores of Lake Superior, both in Canada and this coun try, where it is found imbedded in trap, intruded through secondary rocks; per haps this is the largest district of native copper in the world. The mass disco vered by Sehoolcraft on the west bank of the river Onoutagon weighs 12,200 Ibs. It is now at Washington. Large masses of pure copper are quarried at the several mines in that region (Minesota) to which attention was first called by Dr. Hutton.
Some of these veins contain 10 per cent of silver, which brings its value up to between four and five thousand dollars per ton. The Eagle Harbor Mining Company drifted along a piece of na tive copper ninety feet without finding its length and four feet downwards, without reaching its depth; its average thickness was 18 inches. The veins vary in thickness from 6 inches to 2 feet branching east and west, in small strings 2 inches thick, and 12 to 24 inches .long. The trap in the interstices are charged with native copper to about 50 per cent. There are six very profitable veins in this shore. Dr. Jackson has shewn that these mines were worked by the native Indians many years back. Congress, in 1847, di rected a survey of these mines to be made ; the report has not yet been sent in. In the working of the Cliff and Mine sota mine the difficulty has been to get away pieces small enough. Seven pieces taken from the Cliff mine in 1850 weighed 29,852 lbs., and 4 from Minesota weighed 14,641 lbs. The latter company smelt their copper in New York. The copper is chiselled away with heavy hammers.
The pyritic ores are the vitrious copper ore, which consists of 81 copper and 19 sulphur, found in the II. S. in old red sandstone. The purple copper ore Con tains iron with sulphur : it is not found in quantity. The grey copper ore con sists of copper 52, iron 23, and 14 sul phur. It occurs plentifully in Russia, Chili, and Mexico.
Yellow copper ore is the most abun dant ore, found plentifully in this north ern and southern continent. It contains copper 30, iron 32, sulphur 36; lead and arsenic 3.
The red oxide, or tile ore, is the richest variety, containing 88•5 per cent of cop per. It occurs in Peru and Chili. Azure
copper and malachite are carbonates ; they are found in Pennsylvania and Lake Superior. The finest specimens of mala chite are from the Siberian Ural Chain in Russia, where it occurs so massive that large doors 30 feet by 18 have been cut out of the mineral, and are now exhibited in the Crystal Palace, London.
The ores are repeatedly roasted and fused to drive off the sulphur, and the oxide of copper is ultimately reduced by the joint agency of heat and carbon. Cop per is distinguished by its color. Its spe cific gravity is 8.6. It is ductile and mal leable, and requires a temperature equal to about 2000° of Fahrenheit's scale for its fusion ; that is, nearly a white heat. Ex posed to air and moisture, copper gradual ly becomes covered by a green rust; heated red-hot, it absorbs oxygen, and is super ficially converted into a black oxide, which is the basis of the principal salts of cop per ; it consists of 32 copper and 8 oxy gen. It forms blue or green salts with the acids ; of these the sulphate of copper, or blue vitriol, is a good example. The salts of copper are poisonous ; and in consequence of the use of copper vessels for culinary purposes, food is sometimes contaminated by them. It is detected when in very minute quantities by the bright blue color produced by the addi tion of liquid ammonia, and by a brown precipitate with ferrocyanate of potash. A clean plate of iron dipped into R. solu tion containing copper becomes covered with the latter metal in a metallic state.
Two improvements in the smelting of copper ores have been suggested. One is to roast the sulphuretted copper ores with silt. The sulphur is converted into sulphuric acid, which seizes on the soda of the salt. Its chlorine passes to the copper, forming a chloride, which can be dissolved out by water. The copper is separated from this solution by pieces of iron dropped into it.
The other mode is by roasting to con vert the ore into a sulphate of copper, and dissolve this in water. The copper is thrown down by iron as in the first instance. (See METALLURGY.) Bronze and Bell Metal are alloys of cop per and tin. They are melted" in cruci bles, and cast in charcoal m An alloy of 100 copper and 4 of tin makes a good metal for medals.
Copper 100, and tin 14, affords a metal for edge tools equal in hardness to steel. Cymbal and Gong Metal consists of copper 100, and tin 25. After being heated it should be suddenly cooled.
For White Copper, see GERMAN &MYER.
Copper may be tinned by placing a sheet of tin on a well polished surface of copper, and subjecting them to a strong heat, a little resin or muriate of ammoni um being sprinkled between the plates to prevent oxidation.