Mineral ore

“ Replacement implies the precipitation of the ore and gangue, molecule by molecule, in the position of the original minerals but without, as in pseudomorphs, the necessary reproduction of crystalline forms. Some waterway must of course introduce the ore-bearing solutions, but it may be slight compared with the great size of the resulting ore-bodies. Lead and zinc ores, often carrying some silver, are those most widely distributed, as they were also the earliest recognized in deposits of this character. More than any other metals their association with limestone is pronounced. ”

“ Native metals not being compounds were not considered ores. The product of the copper mines on Keweenaw Point, Lake Superior, was, and to a great extent is still, called copper rock rather than copper ore, and native gold in quartz is often described as gold quartz rather than gold ore, but these restrictions are gradually disappearing. An ore may therefore be defined as a metalliferous mineral or aggregate of metalliferous minerals mingled with a greater or less amount of barren materials called the “gangue,” and yet rich enough to be mined at a profit. ”

“ The normal annual production of iron ore in Greece has been in the neighborhood of 400,000 tons.
Canada. —Small iron-ore deposits occur in New Brunswick and Nova Scotia. In Ontario there are two principal iron-ore districts—the Atikokan and the Michipicotan ranges. The ore in the former is magnetite, and in the latter hematite and siderite with some limonite. The ores of western British Columbia are largely magnetite. The principal deposits are on Texada and Vancouver islands, where the ore is of excellent grade, averaging 63 per cent. iron, 0.02 per cent. phosphorus and 4 to 10 per cent. ”

“ Perhaps no other portion of the earth's surface is so rich in mineral resources as that which has been covered by these observations, and nowhere else is to be found as great a variety of ore deposits, or those which illustrate as well their mode of formation. This is so true that it maybe said without exaggeration that no one can intelligently discuss the questions that have been raised in regard to the origin and mode of formation of ore bodies without transversing and studying the great mining belt of our Western States and Territories. ”

“ When our mining experts discover a mineral belt containing precious metals or copper, iron, lead, nickel, platinum, cobalt, quicksilver, manganese or any other ore used in manufactures and the arts, the first thing we do is to sink a shaft on the most likely ore chimney and at every one hundred feet in depth we run levels to develop it and if we continue to find ore as we go down and the ground requires drainage, we survey for a drainage tunnel that will drain the mine at the greatest depth, even if we have to run a tunnel ten miles. ”

“ Since then development has considerably increased these reserves. In addition there is estimated to be 1,600,000 tons of low-grade ore averaging 5.1 ounces of silver, 7.5 per cent. lead, 4.8 per cent. zinc, and 0.2 per cent. copper per ton, with excellent prospects of larger developments. A large tonnage of gossan outcrop ore containing 4 or 5 ounces silver, 4 to 5 per cent. lead, and a little zinc is cheaply mined and available as siliceous flux. The essential constituents of the ores are galena and sphalerite with a little pyrite and chalcopyrite. All of the ore is argentiferous. ”

“ The ore used is the common sulphuret, with a foliated, glittering and cubical fracture. It occurs with scarcely any adhering gangue. Cubical masses of it are found, at some of the diggings, which are studded over with minute crystals of calcareous spar. These crystals, when examined, have the form of the dog-tooth spar. This broad, square-shaped, and square-broken mineral, is taken from east and west leads, is most easy to smelt, and yields the greatest per centum of lead. It is estimated to produce fifty per cent. ”

“ If the ore does not possess this property on mere exposure to air and moisture, it is broken into pieces and laid upon a bed of brushwood and small coal, to the depth of about four feet, when the pile is fired and fresh lumps of the alum-mineral thrown on, until the mass becomes of considerable height and size. The combustion, as soon as established, is conducted with a smothered fire, until the calcination is complete; care being taken to prevent fusion, or the disengagement of either sulphurous or sulphuric acid, from contact between the ignited stones and the carbonaceous fuel. ”

“ When we compare the first and second tabulations with the third it is at once apparent that with the possible although only occasional exception of iron the production of an ore-body from the normal rocks which constitute the outer mass of the earth requires the local concentration of each of the metals by one or several geological processes, and to a degree that is only occasionally developed in the ordinary course of nature. ”

“ The stamps crush the ore to a fine sand more easily and rapidly than could be done by any other method. Water is kept running over the ore, and as fast as it is crushed sufficiently fine for the particles to pass through a wire screen, the water with which they are mixed is allowed to flow over large plates of copper which have been coated with quicksilver. The latter mineral has an attraction for gold, and so catches and holds most of the particles, no matter how small they are. ”

“ It is only after a sense of security in gold parting has been acquired, that the attack of an ore can be profitably accomplished, and even then simple and easy ores should be first taken, passing on to others more difficult, either because of a more complex mineral composition or a difficulty in sampling. ”

“ Considerable amounts of iron ore are also consumed annually for flux in the smelting of silver, copper, lead, and other metalliferous ores.
Iron and its products are more widely used than any other metal; and the yearly production of pig iron makes up 94 to 96 per cent. of the total amount of all the metals produced in the world, and in normal times averages about 80,000,000 tons annually. ”

“ To find the number of cubic feet per fathom of matter in a vein, multiply its thickness in inches by 3. Great care is requisite in estimating the ore in a vein or the amount of mineral in sight. Very clever men often make grave mistakes in such calculations.
A MAKE-SHIFT FLUX.
Rough smelting may be done with powdered white glass, though either borax or carbonate of soda is better. As soon as the gold is melted and the flux fluid and still, remove the bulk of the flux with an iron spoon, and pour the metal into a clay mould. Crush the flux for gold. ”

“ There are many naturally-existing mineral mixtures in the crushing of which a similar result occurs in a very marked degree; and, indeed, there are none which do not show the peculiarity more or less, because the constituents of an ore are never of exactly the same degree of hardness. When the worthless parts are the softer and therefore have the greater tendency to "slime," the ore is very readily dressed to a high percentage by means of water. ”

“ The tin-smelting capacity of the world is approximately 154,000 tons, whereas the world’s production of tin ore is equivalent to approximately 130,700 tons. It is evident that, unless greater production is forthcoming, some smelters will be idle, and it is a reasonable surmise that neither the British nor Dutch smelters will lack ore. ”

“ Of far the greatest importance of all the ore-bodies in troughs are the iron ores of the Lake Superior region, now the most productive of all the iron-mining districts. In a series of sedimentary formations, generally of Huronian age, and with associated eruptives, there occur strata consisting of a cherty iron carbonate, which were probably originally marine deposits akin to glauconite. They rest upon relatively impervious rocks, and are often penetrated by basaltic dikes. ”

“ The silicate gangue ore bodies carry rhodonite, garnet and quartz and are richer in zinc and silver than those of calcite gangue.
Eight mining companies are now at work. In the order of the importance of their output and ore reserves, these companies are: Broken Hill South Silver Mining Co.; Broken Hill North Mining Co.; Zinc Corporation; Sulphide Corporation; British Broken Hill Proprietary Co.; Broken Hill Proprietary Co., Block 10; and Broken Hill Proprietary Co., Block 14. The estimated ore reserves of all the mines approximate 12,000,000 tons. ”

“ After being thus freed from the admixture of other minerals, the ore is usually roasted or burned, to drive off any traces of sulphur it may contain; it is afterwards heated to redness with blind coal or culm, and a small portion of lime, when the melted metal separates from the dross, and runs into cavities prepared for its reception. It is afterwards refined by being remelted, and other impurities separated, which either sink or float on the surface. The purest metal is yielded by the ore called stream-tin, which is smelted with charcoal instead of coal. ”

“ The ore deposits are usually discovered by the cherty masses of silicious rock, which, being harder than the limestone, stand out from its weathered surface in bunches and small, vein-like masses. Often in 77 breaking the cherty rocks, stains of copper carbonate are found, and from such rock silver, and sometimes gold, is obtained. Numerous shafts, cuts, and tunnels have been made on these claims, twenty or more in number, and in every one ore of good grade has been found, although the quantity is usually small. ”

“ Lead, iron, coal, gypsum, manganese, zinc, antimony, cobalt, ochre of various kinds, common salt, nitre, plumbago, porphyry, jasper, chalcedony, buhrstone, marble, and freestone, of various qualities. The lead and iron ore are literally exhaustless, and of the richest quality. To say there is probably iron ore enough in this region to supply the United States with iron for one hundred thousand years to come, would not be extravagant. Here, too, is water power in abundance, rapid streams, with pebbly beds, forests of timber, and exhaustless beds of bituminous coal. ”

“ The ores when dug from the mine are generally stamped into powder, then “roasted,”—that is, made hot, and kept so for some time to drive off water, sulphur, or arsenic, which would prevent the “fluxes” acting properly. The fluxes are substances which will mix with, melt, and separate the matters to be got rid of, the chief being charcoal, coke, and limestone. The ore is then mixed with the flux, and the whole raised to a great heat; as the metal is separated it melts, runs to the bottom of the “smelting furnace,” and is drawn off into moulds made of sand ”

“ In the case of magnetic ores, roasting converts the ferrous oxide into ferric oxide, which lessens the possibility of the iron becoming mixed with the slag, thereby preventing considerable loss of metal.
Ore is frequently calcined in open heaps, but in more modern practice stalls or kilns are employed. Where fuel is cheap and space is abundant, the first process may be used. A layer of coal a few inches thick is laid on the ground, and a layer of ore is spread upon it; then coal and ore are laid in alternate layers until the pile is from 4 to 9 feet high. ”

“ In really successful mining it is in the last degree important that the mode of extraction of metals in the most scientific manner should be thoroughly understood, but as a general rule the science of metallurgy is but very superficially grasped even by those whose special business it is to treat ore bodies in order to extract their metalliferous contents, and whether in quartz crushing mill, lixiviating, or smelting works there is much left to be desired in the method of treating our ores. ”

“ The earthy materials of the ore with the flux form a fluid slag, while the action of the fuel, or other chemical action, produces a molten metal in some cases or, in other cases, a fused mixture of sulphides, called matte, which is much richer than the original ore in the amount of valuable metal it contains. In iron-smelting the ore, mixed with coke or coal as fuel and with limestone as flux, is fed in at the top of an enormous blast-furnace, a structure somewhat like a barrel in shape, but slenderer and much narrower at the bottom than elsewhere. ”

“ For instance, in ordinary times considerable quantities of high-phosphorus iron ores are mined; but, because of the fact that such ores require more time for conversion into steel, war-time practice concentrated on the higher-grade, low-phosphorus ores, resulting in an unbalanced production which in some cases amounted almost to robbing of ore deposits. In the case of coal, quantity was almost the only consideration; it was impossible to grade and distribute the coal to meet the specialized demands of industry. ”

“ Precious metals (gold, silver, palladium, and platinum) were found mainly in association with such base metals as copper, lead, and zinc. Industrial minerals are represented by a broad range of carbonate and silicate rocks, clays, gravels and sands, and volcanic material. Mineral fuels included coal (lignite) , natural gas, and petroleum.
Until the early 1990s, the mining, processing, and downstream exploitation of base metals established the region as a major European source of copper, lead, and zinc and a major world producer of chromite. ”

“ Persons unacquainted with minerals would be unable to discover the slightest affinity between the rough ironstone as brought up from the mine, and the iron or steel of commerce. To unpractised eyes they would seem to possess no properties in common, and it is only after subjecting the stone to severe processes of manufacture that usable metal can be obtained from it. The effectual reduction of the ore requires an intense heat, maintained by artificial methods, such as furnaces and blowing apparatus. ”