Copper ore

“ Copper in the ore is often blended with several other metallic substances, and with volatile minerals, such as Sulphur and Arsenic. Copper ores also frequently participate [Pg 263] of the nature of the pyrites, containing a martial and an unmetallic earth, both of which are entirely refractory, and hinder the ore from melting. In this case you must add equal parts of a very fusile glass, a little borax, and four parts of the black flux, to facilitate the fusion. ”

“ Fox adds,—"There are, however, many instances of tin ore accompanying copper ore to a great depth; and in Dolcoath mine it is found in a copper lode more than 200 fathoms below the surface, and even under the copper." Mr. Carne observes,—"In general an ochreous oxide of iron (gossan) is found in the upper part of the copper veins, to which sulphuret of iron ('mundic') frequently succeeds, below which the miners confidently expect to obtain copper ore." ”

“ He pointed out several new forms of crystals in the slags from his blast furnaces, and he also beautifully illustrated the theory of the formation of native copper from the vaporized chloride of copper, while working the Atacamite of Peru.
"The most important of his labors were of an eminently practical nature, such as discovering the best and most economical methods of mixing the various copper ores of commerce, so as to make one ore flux another, and thus to obtain the largest yield of metal at the least expense. ”

“ A white crystaline stone is also found to contain a great quantity of yellow copper. The lodes of copper ore generally lie deeper than those of tin, and its ores are mostly of the pyritous and sulphurated kinds, with more or less arsenic. “The lodes, both of tin and copper, appear most frequently to have granite for their country, and to make an angle from 60° to 76° with the horizon.” The matrices of copper ore are very numerous. Among the blue ores, there is one of an extremely fine blue earth. ”

“ A small United-States coin is termed a “nickel.”
Fig. 411.—Native copper.
Copper is the next metal we have to notice. It has been known for centuries. It is encountered native in many places. The Cornish copper ore is the copper pyrites. The fumes of the smelting works are very injurious, containing, as they do, arsenic and sulphur. The ground near the mines is usually bare of vegetation in consequence of the “smoke.” Sheet copper is worked into many domestic utensils, and the alloy with zinc, termed Brass, is both useful and ornamental. ”

“ The further treatment of the converter metal depends to a large extent upon its composition, and the purpose for which it is intended. The matte-smelting operations on copper ores bring about the elimination of the greater part of the constituents accompanying the copper. The converter-grade matte may, however, in addition to the copper, iron and sulphur, also contain considerable proportions of easily reducible impurities of the ore, possessing a greater tendency to enter the matte than to be oxidised and eliminated in the slag. ”

“ Rich copper ores are also found in the Cape of Good Hope, Abyssinia, and equatorial Africa. Large and excellent deposits of iron ore have been found in the Transvaal and in Algiers, and a railroad 20 miles long has been built to carry it from the Algerian mines to the sea. Very many tribes in equatorial and Central Africa work both iron and copper ores into different shapes and uses, showing that the ore-beds must be widely distributed. ”

“ The strike of this shoot of ore is north 50° west, dipping northeast at an angle of 70°. At the depth of 65 feet below the croppings, in sinking a winze, which in its downward course follows a slip northward but is vertical as compared with the dip of the vein, a bunch of high-grade, partly oxidized copper ore was discovered. Further development discovered other pockets or bunches of copper ore carrying usually 68 about 15 ounces in silver per ton. When a depth of 120 feet had been reached a crosscut tunnel was run in 235 feet. ”

“ The Fusion of Ores in Reverberatory and Cupola Furnaces.—After the ore has been partially calcined, it is smelted to extract its earthy matter and to concentrate the copper with part of its iron and sulphur into a matte. In reverberatory furnaces it is smelted by fuel in a fireplace, separate from the ore, and in cupolas the fuel, generally coke, is in direct contact with the ore. When Swansea was the centre of the copper-smelting industry in Europe, many varieties of ores from different mines were smelted in the same furnaces, and the Welsh reverberatory furnaces were used. ”

“ A large furnace and a Bessemer converter, the pair capable of making a million pounds of copper a month from a low-grade sulphuretted ore, will not occupy a space of more than 25ft. by 100ft.; and whereas, in making metallic copper out of a low-grade sulphuretted ore, one day’s labour used to be expended on every ton of ore treated, to-day one day’s labour will carry at least four tons of ore through the different mechanical and metallurgical processes necessary to reduce them to metal. ”

“ By the present methods of exploitation, the daily output of ore will shortly be twenty tons per day; and this ore, with proper plant for concentration, could be brought up to 33 per cent. of copper, worth £16 10s. per ton. The carbonates of copper which the ore carries could, by proper treatment, be made to yield from sixty per cent. to eighty per cent. of copper suitable for smelting. But there is an alternative scheme for the complete exploitation of the property, by which 100 tons of copper ore, of a value of £550, could be raised and treated per diem. ”

“ The metal occurs in small quantities at Bonmahon (Waterford) ; copper and cobalt at Mucross, and grey copper ore in Cork, Kerry, Tipperary, and Galway. In 1855 some 1157 tons were shipped to Swansea.
The Greenlanders and Eskimos cut and hammer their pure native copper, without smelting, into nails, arrow-piles, and other tools and weapons. Mackenzie (second voyage) tells us that pure copper was common among the tribes on the borders of the Arctic Sea, whose arrow-heads and spear-heads were cold-wrought with the hammer. ”

“ Domestic ore ranges from $10 to $12 a ton, while the pure imported ores are worth $21 a ton. The yearly consumption in the United States is about 16,000 tons, and the American production 100 tons. This ore is useful as a lining for furnaces, and the demand promises to become important. Newfoundland is said to contain large deposits.
Copper. Native copper occurs in the Lake Superior region, but the demands of commerce are supplied from chalcopyrite or copper pyrites, and tetrahedrite or gray copper ore. Many different ores of copper may exist in the same vein. ”

“ Traces of copper ore in the trap-rock were first noticed on the easterly side of Keweena Point, and near the commencement of the trap formation. This ore, which is an impure copper black, was observed in a vein of variable thickness, but not in any part291 exceeding 21⁄2 inches; it is sufficiently compact and hard to receive a firm polish, but it is rather disposed to break into small irregular masses. ”

“ The metal is so pure that it can be refined by a continuous operation in the same furnace.
Wet Methods for Copper Extraction.—Wet methods are only employed for low grade ores (under favourable circumstances ore containing from 1⁄4 to 1% of copper has admitted of economic treatment) , and for gold and silver bearing metallurgical products.
The fundamental principle consists in getting the ore into a solution, from which the metal can be precipitated. The ores of any economic importance contain the copper either as oxide, carbonate, sulphate or sulphide. ”

“ To chemical science, therefore, we are indebted for such an ample supply of this valuable metal. It is asserted, that a large copper mine has been worked for some time in the state of New-Jersey in America, and that the ore raised there is brought to this country to be smelted. Native oxides of copper are found in Cornwall and in South America. Carbonate of copper occurs as a natural production in two varieties, called malachite and mountain green. Sulphate of copper, of a very rich quality, is also found in the state of Connecticut. The stream in its course destroys vegetation ”

“ The weighed quantity of ore is dissolved by evaporating with nitric acid and taking up with hydrochloric, as already described. Any coloured residue which may be left is generally organic matter: it is filtered off, calcined, and any copper it contains is estimated colorimetrically. Nearly always, however, the residue is white and sandy. The copper is separated from the solution as sulphide by means of a rapid current of sulphuretted hydrogen. ”

“ The roasted ore is then smelted to a mixture of copper and iron sulphides, known as copper “matte” or “coarse-metal,” which contains little or no arsenic, antimony or silica. The coarse-metal is now smelted, with coke and siliceous fluxes (in order to slag off the iron) , and the product, consisting of an impure copper sulphide, is variously known as “blue-metal,” when more or less iron is still present, “pimple-metal,” when free copper and more or less copper oxide is present, or “fine” or “white-metal,” which is a fairly pure copper sulphide, containing about 75% of the metal. ”

“ The very great variety of purposes for which the metal called copper is used, renders it one of the most valuable productions of this country, and several very important manufactures would be incomplete without it, since it is the principal material of which many large vessels are formed, and is also largely employed as an alloy for other metals. Although the metal is sometimes found in a pure or native state, its most abundant ore is that known as copper pyrites, of which there are many kinds. ”

“ In the reduction of the oxides of this group, no sublimate is visible upon the charcoal.
(a.) Copper (Cu) .—This metal occurs in the metallic state, also as the protoxide, and as oxides combined with acids in different salts (carbonate of copper as malachite, etc.) The sulphide of copper is the principal ore of copper occurring in nature. In the metallic state, copper is of a red color, has great lustre and tenacity, is ductile and malleable, and crystallizes in octahedrons and cubes. It melts at a bright red heat, is more difficult than silver to fuse, but fuses more readily than gold. ”

“ A variety of copper ornaments are worn by the Kafirs of the northern parts of the Transvaal who have known how to extract the metal from the mineral and to smelt it into pure ore. No mining operations in search of copper have, as I believe, yet been carried on by white men in the country. At an Agricultural Show which was held in 1876 at Potchefstroom, the chief town in the southern part of the Transvaal, prizes were awarded for specimens of the following minerals found in the country itself. Gold-bearing quartz, alluvial gold, copper, tin, lead, iron, plumbago, cobalt, and coal. ”

“ The ore, as at first found in the mines of Copiapó, has barely 18 to 36 per cent. of copper, and has to undergo six or seven smeltings before it becomes sufficiently pure to be sold at a profit in the markets of Europe. The smelting-furnace produces about seven tons of copper per diem, at a consumption of 60 tons of coal, [121] which is imported from 342Swansea, partly from Pennsylvania, and is worth 12 to 15 dollars per ton of 2240 lbs. ”

“ It occurs extensively in Montana, Arizona, Tennessee, Canada, Chili, Japan, Spain, Cornwall, etc.
Chalcopyrite ores vary considerably in copper contents; thus Tennessee ores contain about 2·5 per cent. of copper, Montana ores 5 to 51⁄2 per cent. (with gold and silver valued at about £11 per ton of copper) , whilst the Arizona ores vary, being often rich.
Chalcocite (also known as copper glance or redruthite) is much less important. The copper contents are 79·8 per cent. when pure, but such a condition is rare, although the ore seldom contains less than 50 per cent. of copper. ”

“ In the bosom of mountains where copper is found, they hollow out galleries which go down deep into the earth. There workmen called miners, with lamps to light them, attack the rock with great blows of the pick, while others carry the detached blocks outside. These blocks of stone in which copper is found are called ore. In furnaces made for the purpose they heat the ore to a very high temperature. The heat of our stove, when it is red-hot, is nothing in comparison. The copper melts, runs, and is separated from the rest. ”

“ It needs not to be insisted upon that much attention ought to be given to free copper from arsenic, which is so very liable to render it brittle. When a pound or two of the ore is given to the sample-trier, as a fair sample of 50 or 100 tons, his report is but too often grounded on the weight of the prill he has obtained from a given quantity of the ore, without reference to the substances with which it may be alloyed, which indeed his skill does not enable him to detect. ”

“ If no action is noticed, even after heating the dish, the dust is genuine. As "dust" is sometimes merely copper coated with gold, the better plan is to cut all the larger grains in two, so that the acid may attack the copper should it be present.
Copper. Copper is a very easy mineral to test for. First crush the ore and dissolve it in nitric acid by heating. Then dilute with some water, and add ammonia. The solution should turn dark blue. The carbonate ores of copper do not extend deep in the mine. Their places are taken by copper pyrites. ”