Ores sentence example

ores
  • Gold, lead, copper and iron ores occur as veins.
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  • Iron ores have been found in most of the states, and are especially abundant in Minas Geraes.
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  • The problem of the profitable treatment of the sulphide ores has been practically solved here.
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  • In the blast-furnace all lead ores are successfully smelted.
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  • This has led to the estimation of sugar by means of the polarimeter, and of the calorific power of fuels, and the valuation of ores and metals, of coal-tar dyes, and almost all trade products.
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  • He wrote Correlation Papers - Archaean and Algonkian (1892), Some Principles Controlling the Deposition of Ores (1901).
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  • Lead ores are smelted in the reverberatory furnace, the ore-hearth, and the blast-furnace.
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  • In smelting at once in the same blast-furnace ores of different character, the old use of separate processes of precipitation, roasting and reduction, and general reduction prevailing in the Harz Mountains, Freiberg and other places, to suit local conditions, has been abandoned.
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  • Ores are smelted raw if the fall of matte (metallic sulphide) does not exceed 5%; otherwise they are subjected to a preliminary oxidizing roast to expel the sulphur, unless they run too high in silver, say 100 oz.
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  • In making up a charge, the ores and fluxes, whose chemical compositions have been determined, are mixed so as to form out of the components, not to be reduced to the metallic or sulphide state, typical slags (silicates of ferrous and calcium oxides, incidentally of aluminium oxide, which have been found to do successful work).
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  • The lead produced in the reverberatory furnace and the ore-hearth is of a higher grade than that produced in the blast-furnace, as the ores treated are purer and richer, and the reducing action is less powerful.
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  • The gold is found in minute particles arid in the richest ores the metal is rarely in visible quantities before treatment.
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  • The resulting compound, nickel carbonyl, which was described to the Chemical Society in 1890, is both formed and decomposed within a very moderate range of temperature, and on this fact he based a successful process for the extraction of nickel from its ores.
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  • Molybdenum occurs in nature chiefly as the minerals molybdenite (MoS 2) and wulfenite (PbMo04), and more rarely as molybdic ochre (Moos) and ilsemannite; it also occurs in many iron ores.
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  • These harbours on the eastern side of Sydney are mainly frequented by cargo boats trading in coal, corn, frozen meat, wool, hides and various ores.
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  • The Bolivian tin ore is treated by first extracting the silver by amalgamation, &c., and afterwards concentrating the residues; there are, however, considerable difficulties in the way of treating the poorer of these very complex ores, and several chemical processes for extracting their metallic contents have been worked out.
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  • In the article on Mineral Deposits the distribution and mode of occurrence of the useful minerals and ores are fully discussed.
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  • In the case of the cheaper and more abundant minerals, such as coal and iron ore, and of large deposits of low-grade ores, the extent and character of the deposit can generally be determined by surface examinations at comparatively small expense.
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  • The subdrift system requires a smaller amount of narrow work in excavating the necessary haulage roads, and is therefore better adapted to hard ores in which such narrow work is expensive.
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  • On the other hand, as in mining ores containing lead, arsenic and mercury, the dust may be poisonous.
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  • The main mineral deposits are the nickel ores, occurring as veins of garnierite, associated with peridotite dikes, in the ancient rocks of the eastern slope of the island.
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  • The island imports wines, spirits, tissues, clothing and ironmongery; and exports ores, nickel, cobalt and chrome (which represent over three-quarters of the total exports in value), preserved meats and hides, coffee, copra and other colonial produce.
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  • As ores of zinc are usually shipped before smelting from widely separated places - Sweden, Spain, Algiers, Italy, Greece, Australia and the Rocky Mountains region of North America - it is important that they be separated from their mixtures at the mines.
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  • Neither mechanical nor magnetic concentration can effect much in the way of separation when, as in many complex ores, carbonates of iron, calcium and magnesium replace the isomorphous zinc carbonate, when some iron sulphide containing less sulphur than pyrites replaces zinc sulphide, and when gold and silver are contained in the zinc ore itself.
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  • Hence only in exceptional circumstances is it possible to utilize a large class of widely distributed ores, carrying from Io to 35 per cent.
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  • The ores of the Joplin district, in the Ozark uplift in the Mississippi Valley, are remarkable in that they are specially adapted to mechanical concentration.
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  • For the desulphurization of zinc blende where it is not intended to collect and save the sulphur there are many mechanical kilns, generally classified as straight-line, horse-shoe, turret and shaft kilns; all of these may be made to do good work on moderately clean ores which do not melt at the temperature of desulphurization.
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  • It is generally recognized that the purest ores produce the purest metal.
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  • Grades of commercial zinc are usually based on selected ores, and brands, when they mean anything, usually mean that the metal is made from certain ores.
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  • Ashcroft patented a process of dealing with complex ores of the well-known Broken Hill type, containing sulphides of silver, lead and zinc, but the system was abandoned after a long trial on a practical scale.
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  • Traces of ancient workings were found in several places, but the ores did not contain gold in paying quantities.
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  • In 1885 the brothers Cowles patented a process for the electrothermal reduction of oxidized ores by exposure to an intense current of electricity when admixed with carbon in a retort.
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  • The gold ores of Peru are usually found in ferruginous quartz.
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  • The dried dung of the llama (taquia) is generally used as fuel, as in pre-Spanish times, for roasting ores, as also a species of grass called ichu (Stipa incana), and a singular woody fungus, called yareta (Azorella umbellifera), found growing on the rocks at elevations exceeding 12,000 ft.
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  • The methods formerly employed in reducing ores were lixiviation and amalgamation with quicksilver, but modern methods are gradually coming into use.
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  • The metal generally occurs as sulphide of mercury (cinnabar), but the ores vary greatly in richness - from 21 to 20%.
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  • Iron ores are found in Piura, the Huaylas valley, Aya, and some other places, but the deposits have not been worked through lack of fuel.
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  • The manufacturing industries of Peru are confined chiefly to the treatment of agricultural and mineral products - the manufacture of sugar and rum from sugar cane, textiles from cotton and wool, wine and spirits from grapes, cigars and cigarettes from tobacco, chocolate from cacao, kerosene and benzine from crude petroleum, cocaine from coca, and refined metals from their ores.
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  • The ores are generally of good quality, and are easy of extraction.
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  • The richest mining districts are those of Cadereyta and Toliman, where there are metallurgical works for the reduction of ores.
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  • Old schists, free from fossils and rich in quartz, overlie it in parallel chains through the whole length of the peninsula, especially in the central and highest ridges, and bear the ores of Chu-goku (the central provinces), principally copper pyrites and magnetic pyrites.
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  • This group extends east of the Enns, and contains the Erzberg (5000 ft.) celebrated for its iron ores.
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  • Lead ores (chiefly argentiferous galena) and building stone are found, and iron ore is distributed over the hilly country.
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  • The exports include copper and silver and their ores, nitrate of soda, borax, guano and other minerals in small quantities.
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  • In the alluvial deposits the associated minerals are chiefly those of great density and hardness, such as platinum, osmiridium and other metals of the platinum group, tinstone, chromic, magnetic and brown iron ores, diamond, ruby and sapphire, zircon, topaz, garnet, &c. which represent the more durable original constituents of the rocks whose distintegration has furnished the detritus.
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  • Of this increase, a considerable part was derived from gold-quartz mining, though much was also obtained as a by-product in the working of the ores of other metals.
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  • In the Knox and Boss mills, which are also employed for the amalgamation of silver ores, the grinding is effected between flat horizontal surfaces instead of conical or curved surfaces as in the previously described forms.
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  • Gold in galena or other lead ores is invariably recovered in the refining or treatment of the lead and silver obtained.
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  • Pyritic ores containing copper are treated by methods analogous to those of the copper smelter.
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  • In Colorado the pyritic ores containing gold and silver in association with copper are smelted in reverberatory furnaces for regulus, which, when desilverized by Ziervogel's method, leaves a residue containing 20 or 30 oz.
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  • This is smelted with rich gold ores, notably those containing tellurium, for white metal or regulus; and by a following process of partial reduction analogous to that of selecting in copper smelting, " bottoms " of impure copper are obtained in which practically all the gold is concentrated.
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  • - In this process moistened gold ores are treated with chlorine gas, the resulting gold chloride dissolved out with water, and the gold precipitated with ferrous sulphate, charcoal, sulphuretted hydrogen or otherwise.
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  • The process is rarely applied to ores direct; free-milling ores are generally amalgamated, and the tailings and slimes, after concentration, operated upon.
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  • According to Egleston the loss may be from 40 to 90% of the total gold present in cupriferous ores according to the temperature and duration of calcination.
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  • It is best adapted for free-milling ores, especially after the bulk of the gold has been removed by amalgamation.
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  • The ores, having been broken and ground, generally in tube mills, until they pass a 150 to 200-mesh sieve, are transferred to the leaching vats, which are constructed of wood, iron or masonry; steel vats, coated inside and out with pitch, of circular section and holding up to woo tons, have come into use.
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  • The liquors are run off from the vats to the electrolysing baths or precipitating tanks, and the leached ores are removed by means of doors in the sides of the vats into wagons.
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  • The slime so obtained consists of finely divided gold and silver (5-5 0%), zinc (30-60%), lead (io%), carbon (io%), together with tin, copper, antimony, arsenic and other impurities of the zinc and ores.
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  • West of the Low Tatra extend the Fatra group, with the highest peak, the Great Fatra (5825 ft.), to the south and east of which lie the Schemnitz group, the Ostrowsky group, and several other groups, all of which are also called the Hungarian Ore Mountains, on account of their richness in valuable ores.
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  • The Carpathian system is richer in metallic ores than any other mountain system of Europe, and contains large quantities of gold, silver, copper, iron, lead, coal, petroleum, salt, zinc, &c., besides a great variety of useful mineral.
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  • Bismuth occurs in metalliferous veins traversing gneiss or clay-slate, and is usually associated with ores of silver and cobalt.
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  • Bismuth is extracted from its ores by dry, wet, or electro-metallurgical methods, the choice depending upon the composition of the ore and economic conditions.
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  • The extraction from ores in which the bismuth is present in the metallic condition may be accomplished by a simple liquation, or melting, in which the temperature is just sufficient to melt the bismuth, or by a complete fusion of the ore.
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  • Sulphuretted ores are smelted, either with or without a preliminary calcination, with metallic iron; calcined ores may be smelted with carbon (coal).
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  • Calcination in reverberatory furnaces and a subsequent smelting in the same type of furnace with the addition of about 3% of coal, lime, soda and fluorspar, has been adopted for treating the Bolivian ores, which generally contain the sulphides of bismuth, copper, iron, antimony, lead and a little silver.
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  • Ores containing the oxide and carbonate are treated either by smelting with carbon or by a wet process.
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  • In the wet process the ores, in which the bismuth is present as oxide or carbonate, are dissolved out with hydrochloric acid, or, if the bismuth is to be extracted from a matte or alloy, the solvent employed is aqua regia or strong sulphuric acid.
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  • Other minerals found in small quantities are copper, lead, zinc, iron ores, manganese ores and tin.
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  • Mispickel occurs in metalliferous veins with ores of tin, copper, silver, &c. It is occasionally found as embedded crystals, for example, in serpentine at Reichenstein, Silesia.
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  • No evidence of smelting ores with fluxes is offered, but casting from metal melted in open fires is assumed.
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  • In many deposits of iron ores found in connexion with igneous or metamorphic rocks small quantities of phosphate occur.
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  • The Swedish, Norwegian, Ontario and Michigan mines yield ores of this kind; and though none of them can be profitably worked as a source of phosphate, yet on reducing the ore it may be retained in the slags, and thus rendered available for agriculture.
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  • Silver is chiefly extracted in the Thames district, but other mines containing silver ores have been found.
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  • There are many other valuable ores - copper, iron, lead, zinc, antimony, chrome and manganese.
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  • Gold, silver, copper, lead and a little iron (almost entirely brown ore) are the principal ores of commercial importance found in Washington.
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  • The largest output of each of these ores in 1908 was in Stevens county; Ferry, King and Okanogan counties ranked next in the output of gold; Okanogan and Ferry counties in the output of silver; Okanogan in the output of copper; and King in the output of lead.
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  • About nine-tenths of the gold was got from dry or siliceous ores and about 8% from placer mines; about twothirds of the silver from dry or siliceous ores, about two-ninths from copper ores, and most of the other ninth from lead ores.
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  • The ore yields about 46% of iron, and contains about 2.5% of sulphur, the roasting of the ores being necessaryore-roasting kilns are more extensively used here than in any other place in the country.
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  • Then copper mining rapidly developed and considerable gold was obtained from copper ores.
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  • Until the development of copper mining, silver was produced only in small quantities along with gold, but as much more silver than gold was obtained from the copper ores the value of the silver product increased from $2,630,000 in 1881 to $24,615,822 in 1892.
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  • The product then fell off, but in 1907, when it amounted to 9,317,605 fine ounces, valued at $6,149,619, more than nine-tenths of it was derived from the copper ores in Silverbow county.
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  • It was in 1882 while Marcus Daly was sinking a shaft at Anaconda in preparation for milling gold and silver ores that he discovered the first rich copper ledge.
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  • The smelting and refining of the metal ores is also an important industry.
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  • The city's foreign trade is light (the value of its imports was $859,442 in 1907; of its exports $664,525), but its river traffic is heavy, amounting to about 3,000,000 tons annually, and being chiefly in general merchandise (including food-stuffs, machinery and manufactured products), ores and metals, chemicals and colours, stone and sand and brick.
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  • In other cases, especially near mineral veins, slates are filled with black needles of tourmaline or are bleached to pale grey and white colours, or are silicified and impregnated with mineral ores.
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  • The ores are almost exclusively gold, tellurides being the most characteristic form, and occur in fissure veins.
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  • Some peculiarities of the ores have required the use of new methods in their treatment, and in general the development of mining methods and machinery is of a wonderful character.
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  • From 1722 until the War of Independence the iron-ore product of North and West Maryland was greater than that of any of the other colonies, but since then ores of superior quality have been discovered in other states and the output in Maryland, taken chiefly from the west border of the Coastal Plain in Anne Arundel and Prince George's counties, has become comparatively of little importance-24,367 long tons in 1902 and only 8269 tons in 1905.
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  • Gold, silver and copper ores, have been found in the state, and attempts have been made to mine them, without much success.
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  • Excellent beds of coal are found in different places, especially about Kulja, but the fairly rich copper ores and silver ores have ceased to be worked.
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  • The manufactures are insignificant; and although silver, copper, iron, zinc, lead and marble are said to exist in considerable quantities, the only ores that have been worked are gold, silver and copper.
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  • Mining taxes, which are subject to periodic changes, consist of an initial or registry tax on the claim (pertenencia), an annual or rental tax on each claim, and a tax of 32% (1905) on the export of unrefined gold and silver, 21% on partially refined ores, and 12% on pure silver.
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  • Iron was not known, but copper and tin ores were mined, and the metals combined into bronze of much the same alloy as in the Old World, of which hatchet blades and other instruments were made, though their use had not superseded that of obsidian and other sharp stone flakes for cutting, shaving, &c. Metals had passed into a currency for trading purposes, especially quills of gold-dust and T-shaped pieces of copper, while coco-beans furnished small change.
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  • Manganese ore is the chief mineral, and is extracted for export to the extent of 160,000 to 180,000 tons annually, besides coal, lead and silver ores, copper, naphtha, some gold, lithographic stone and marble.
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  • Minerals.In 1619 the erection of works for smelting the ores of iron was begun at Falling Creek, near Jamestown, Va., and iron appears to have been made in 1620; but the enterprise was stopped by a general massacre of the settlers in that region.
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  • From the middle of the 17th century the smelting of this metal began to be of importance in Massachusetts Bay and vicinity, and by the close of the century there had been a large number of ironworks established in that colony, which, for a century after its settlement, was the chief seat of the iron manufacture in America, bog ores, taken from the bottom of the ponds, being chiefly used.
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  • The development of the coal and iron interests, and the increasing importance of the gold product of the Appalachian auriferous belt, and also of the lead product of the Mississippi Valley, led to a more general and decided interest in geology and mining; and about 1830 geological surveys of several of the Atlantic states were begun, and more systematic explorations for the ores of the metals, as well as for coal, were carried on over all parts of the country then open to settlement.
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  • Of the two classes of iron minerals used as ores of that metal, namely, oxides and carbonates, the latter furnish to-day an insignificant proportion of the countrys product, although such ores were the basis of a considerable part of the early iron industry, and even so late as 1889 represented one-thirteenth of the total.
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  • Of the oxides, various forms of the brown ores in locations near to the Atlantic coast were the chief basis of the early iron industries.
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  • Magnetites were also early employed, at first in Catalan forges, in which by means of a direct process the metal was secured from the ores and forged into blooms without being cast; later they were smelted in blast furnaces.
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  • But in the recent and great development of the iron industry the red haematite ores have been overwhelmingly predominant.
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  • From 1889 to 1907 the average yearly percentages of the red haematite, brown ores, rnagnetite and carbonate in the total ore production were respectively 824, I0I, 7.1 and 0.4.
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  • In the census of 1870 the share of the three varieties appeared almost equal; in 1899 that of the red ores had risen to near two-thirds of the total.
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  • The red and brown ores are widely distributed, every state in the Union in 1907, save Ohio and North Carolina, producing one or both.
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  • With the reservations that only in the case of certain red haematite bedded deposits can any estimate be made of relative accuracy, say within 10%; that the concentration deposits of brown ore can be estimated only with an accuracy represented by a factor varying between 0.7 and 3; and that the great Lake Superior and the less known Adirondack deposits can be estimated within 15 to 20%, the total supply of the country was estimated at 79,594,220,000 long tons73,21o,415,000 of which were credited to haematite ores and 5,054,675,000 to magnetite.
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  • The grade of precious ores hafidled has generally and greatly decreased in recent yearsaccording to the census data of 1880 and 1902, disregarding all base metallic contentsfrom an average commerical value of $29.07 to one of $8.29; nevertheless the product of gold and silver has greatly increased.
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  • This is due to improvements in mining methods and reduction processes, which have made profitable low-grade ores that were not commercially available in 1880.
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  • Since 1825 the total product of lead refined from domestic ores and domestic base bullion was, up to the close of 1908, 7,091,548 short tons.
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  • Considerable quantities of foreign ores and base bullion are also refined in the United States.
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  • The average percentage of metallic recovery from lead ores was about 68%, in 1880, and again in 1902, according to the national censuses of these years.
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  • According to the bureau of the census the value in 1902 of the lead yielded by copper, by non-argentiferous lead and zinc, and by gold and silver ores respectively was $19,053, $5,850,721 and $12,311,239.
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  • This reflects the revolutionary change in the history of lead mining since the first discovery of argentiferous lead ores in the Rocky Mountain states in 1864, which became available only after the building of railways.
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  • Until the completion of the Union Pacific in 1869 there was no smelting of such ores except for their silver contents.
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  • The value of products in 1902 were reported as $340,686 from gold and silver ores, and $8,665,675 from non-argentiferous lead and zinc ores.
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  • The mercurial ores of the Pacific Coast ranges occur in very irregular deposits in the form of strings and bunches, disseminated through a highly metamorphosed siliceous rod~c. The first locality where the metal was successfully mined was at New Almaden, about 100 m.
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  • The production had steadily fallen to 16,984 flasks in 1908, but in the opinion of the United States Geological Survey this reduction is mainly attributable, in recent years at least, to market conditions, and does not truly indicate the exhaustion of the mines, although the ores now available are of low grades, those of New Almaden having shown a decrease in yield from 36.7% in1850-1851to o~74% in 1895-1896, so that only the greatest metallurgical skill and business economy can sustain the mines against a weak market.
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  • Tin ores have been widely discovered, but though much has been hoped for from them, particularly from the deposits in the Black Hills region of South Dakota, there has been no more than a relatively insignificant commercial production.
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  • Metalliferous ores of various kinds occur both in Nova Scotia and in this province, but with the exception of the gold already mentioned, have not yet become the objects of important industries.
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  • The discovery of large deposits of nickel at Sudbury; of extremely rich gold mines on the head-waters of the Yukon, in a region previously considered well-nigh worthless for human habitation; of extensive areas of gold, copper and silver ores in the mountain regions of British Columbia; of immense coal deposits in the Crow's Nest Pass of the same province and on the prairies; of veins of silver and cobalt of extraordinary richness in northern Ontario - all deeply affected the industrial condition of the country and illustrated the vastness of its undeveloped resources.
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  • The total production of all classes of iron ores was 3,782,831 tons in 1905, Alabama ranking third in the Union in this respect.
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  • He was a man of more promise than performance, and his chief achievement was the discovery of the elements iridium and osmium, which he found in the residues from the solution of platinum ores (1804).
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  • Like the other provinces of this region, Antofagasta produces for export copper, silver, silver ores, lead, nitrate of soda, borax and salt.
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  • Iron and manganese ores are also found.
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  • The state ranks second to New York in the value of its manufactures, which increased from $155,044,910 in 1850 to $1,955,551,332 (factory products alone) in 1905, a growth which has been promoted by an abundance of fuel, by a good port on the Atlantic seaboard, by a network of eanals which in the early years was of much importance in connecting the port with the Mississippi river system, by its frontage on Lake Erie which makes the ores of the Lake Superior region easily accessible, and by a great railway system which has been built to meet the demands arising from the natural resources.
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  • An oolitic structure is sometimes present, and the ores are generally phosphatic, and may contain perhaps 30% of iron.
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  • It often happens that analyses of brown iron ores reveal a larger proportion of water than required by the typical formula of limonite, and hence new species have been recognized.
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  • Toledo is the port of entry for the Miami customs district and is an important shipping point for the iron and copper ores and lumber from the Lake Superior and Michigan regions, for petroleum, coal, fruit, and grain and clover-seed.
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  • Though the mineral products are varied, the supply of ores has hitherto proved scanty; besides which their exploitation is rendered difficult by the lack of labourers, water and wood.
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  • He next devised a plan for manufacturing pure alumina from the natural ores, and finally elaborated a process and plant which held the field for almost thirty years.
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  • Within the Carboniferous rocks, but due to the action of various agencies long after their deposition, are important ore formations; such are the Rio Tinto ores of Spain, the lead and zinc ores and some haematite of the Pennine and Mendip hills and other British localities, and many ore regions in the United States.
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  • A problem to which he returned repeatedly was that of separating nickel and cobalt from their ores and freeing them from arsenic; and in the course of his long laboratory practice he worked out numerous processes for the preparation of pure chemicals and methods of exact analysis.
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  • Foremost among these elements is carbon, which iron inevitably absorbs from the fuel used in extracting it from its ores.
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  • The iron oxide of which the ores of iron consist would be so easily deoxidized and thus brought to the metallic state by the carbon, i.e.
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  • The oxide ores of copper would be deoxidized by the savage's wood fire even more easily than those of iron, and the resulting copper would be recognized more easily than iron, because it would be likely to melt and run together into a mass conspicuous by its bright colour and its very great malleableness.
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  • From this we may infer that copper and iron probably came into use at about the same stage in man's development, copper before iron in regions which had oxidized copper ores, whether they also had iron ores or not, iron before copper in places where there were pure and easily reduced ores of iron but none of copper.
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  • Indeed, though iron ores abound in many places which have neither copper nor tin, yet there are but few places which have both copper and tin.
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  • Impurities.-The properties of iron and steel, like those of most of the metals, are profoundly influenced by the presence of small and sometimes extremely small quantities of certain impurities, of which the most important are phosphorus and sulphur, the former derived chiefly from apatite (phosphate of lime) and other minerals which accompany the iron ore itself, the latter from the pyrite found not only in most iron ores but in nearly all coal and coke.
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  • Ores of Iron.-Even though the earth seems to be a huge iron meteor with but a thin covering of rocks, the exasperating proneness of iron to oxidize explains readily why this metal is only rarely found native, except in the form of meteorites.
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  • They are four important iron ores, magnetite, haematite, limonite and siderite, and one of less but still considerable importance, pyrite or pyrites.
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  • Though it contains far too much sulphur to be used in iron manufacture without first being desulphurized, yet great quantities of slightly cupriferous pyrite, after yielding nearly all their sulphur in the manufacture of sulphuric acid, and most of the remainder in the wet extraction of their copper, are then used under the name of " blue billy " or " purple ore," as an ore of iron, a use which is likely to increase greatly in importance with the gradual exhaustion of the richest deposits of the oxidized ores.
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  • The Ores actually Impure.-As these five minerals actually exist in the earth's crust they are usually more or less impure chemically, and they are almost always mechanically mixed with xlv.
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  • These of course are the oldest of our ores, and from deposits of like age, especially those of the more readily decomposed silicates, has come the iron which now exists in the siderites and red and brown haematites of the later geological formations.
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  • The iron ores of the earth's crust will probably suffice to supply our needs for a very long period, perhaps indeed for many thousand years.
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  • The two assertions are not to be reconciled by pointing out that Professor Tornebohm underestimated, for instance crediting the United States with only 1 1 billion tons, whereas the United States Geological Survey's expert credits that country with from ten to twenty times this quantity; nor by pointing out that only certain parts of Europe and a relatively small part of North America have thus far been carefully explored for iron ore, and that the rest of these two continents and South America, Asia and Africa may reasonably be expected to yield very great stores of iron, and that pyrite, one of the richest and most abundant of ores, has not been included.
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  • Important as these considerations are, they are much less important than the fact that a very large proportion of the rocks of the earth's crust contain more or less iron, and therefore are potential iron ores.
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  • Rock containing 22% of gold is an extraordinarily rich gold ore; that with 21% of copper is a profitable one to-day; that containing 21% of iron is not so to-day, for the sole reason that its iron cannot be extracted with profit in competition with the existing richer ores.
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  • Very few of the ores which are mined to-day contain less than 25% of iron, and some of them contain over 60%.
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  • When, in the course of centuries, the exhaustion of richer ores shall have forced us to mine, crush and concentrate mechanically or by magnetism the ores which contain only 2 or 3% of iron, then the cost of iron in the ore, measured in terms of the energy needed to mine and concentrate it, will be comparable with the actual cost of the copper in the ore of the copper-mines of to-day.
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  • But, intermediate in richness between these two extremes, the iron ores mined to-day and these 2 and 3% ores, there is an incalculably great quantity of ore capable of mechanical concentration, and another perhaps vaster store of ore which we do not yet know how to concentrate mechanically, so that the day when a pound of iron in the ore will cost as much as a pound of copper in the ore costs to-day is immeasurably distant.
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  • On the other hand, the cost of iron ore is likely to rise much faster than that of the potential aluminium ores, clay and its derivatives, because of the vast extent and richness of the deposits of this latter class.
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  • Thus, if the use of ores very much poorer than those we now treat, and the need of concentrating them mechanically, were to double the cost of a pound of iron in the concentrated ore ready for smelting, that would increase the cost of rails by only one quarter.
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  • Hence the addition to the cost of finished steel objects which is due to our being forced to use progressively poorer and poorer ores is likely to be much less than the addition due to the progressive rise in the cost of coal and in the cost of labour, because of the ever-rising scale of living.
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  • The United States mine nearly all of their iron ores, Austria-Hungary, Russia and France mine the greater part of theirs, but none of these countries exports much ore.
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  • In 1905 the Cleveland district in North Yorkshire supplied 41% of the total British product of iron ores; Lincolnshire, 14.8%; Northamptonshire, 13.9%; Leicestershire, 4.7%; Cumberland, 8.6%; North Lancashire, 2.7%; Staffordshire, 6.1%; and Scotland, 5.7%.
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  • The middle states, New York, New Jersey and Pennsylvania, are known to have many great deposits of rich magnetite, which supplied a very large proportion of the American ores till the discovery of the very cheaply mined ores of Lake Superior.
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  • Sweden has abundant, rich and very pure iron ores, but her lack of coal has restricted her iron manufacture chiefly to the very purest and best classes of iron and steel, in making which her thrifty and intelligent people have developed very rare skill.
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  • The American ores now mined are decidedly richer than those of most European countries.
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  • To make a ton of pig iron needs only about 1.9 tons of ore in the United States, 2 tons in Sweden and Russia, 2.4 tons in Great Britain and Germany, and about 2.7 tons in France and Belgium, while about 3 tons of the native British ores are needed per ton of pig iron.
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  • In smelting the rich Lake Superior ores the quantity of slag made was formerly as small as 28% of that of the pig iron, whereas in smelting the Cleveland ores of Great Britain it is usually necessary to make as much.
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  • 80% of phosphorus limits, the use of the process, because there are few ores which can be made to yield so phosphoric a pig iron.
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  • This may not necessarily be true, but the acid variety lends itself more readily to excellence than the basic. A very large proportion of ores.
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  • The increased importance of Germany and Luxemburg may be referred in large part to the invention of the basic Bessemer and open-hearth processes by Thomas, who by them gave an inestimable value to the phosphoric ores of these countries.
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  • He saw all the mechanical difficulties that had to be overcome in mining; he learned the nature and succession of rocks, the physical properties of minerals, ores and metals; he got a notion of mineral waters; he was an eyewitness of the accidents which befel the miners, and studied the diseases which attacked them; he had proof that positive knowledge of nature was not to be got in schools and universities, but only by going to nature herself, and to those who were constantly engaged with her.
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  • Potassium bisulphate is useful in the preliminary treatment of refractory aluminous ores.
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  • The Devonian sandstones contain malachite ores near Kielce, and copper has been worked there since the 15th century, though the mines are now neglected.
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  • The brown iron ores of Kielce contain no less than 40% of iron.
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  • Brown iron ores, appearing in the neighbourhood of Bendzin as lenticular masses 55 ft.
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  • Spherosiderites and brown iron ores are plentiful also in the " Keuper formation."
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  • At the large and important Premier mine in the Transvaal the Elmore process, used in British Columbia and in Wales for the separation of metallic ores, has been also introduced.
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  • The chief exports are iron and other ores, china clay, granite, fish and grain.
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  • Commercially, Cologne is one of the chief centres on the Rhine, and has a very important trade in corn, wine, mineral ores, coals, drugs, dyes, manufactured wares, groceries, leather and hides, timber, porcelain and many other commodities.
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  • It is extracted from the ores in the mines of Freiburg (Saxony), the Harz Mountains, upper Silesia, Merseburg, Aix-la-Chapelle, Wiesbaden and Arnsberg.
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  • Ores, precious metals, asbestos, &c 28,834,050 9,899,450
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  • The volumes of the Scri pi ores contain not only the domestic chroniclers, but also selections from the work of foreign writers who give information about the history of Germanyfor example, the Englishman Matthew Paris.
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  • Mineral ores, tobacco and cigars, coffee, cacao, sugar and rum and cabinet-woods are the main articles of export.
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  • The veins are small, but contain native silver and other rich silver ores running sometimes several thousand ounces per ton, the output being 5,500,000 oz.
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  • Associated with the silver minerals are rich ores of cobalt and nickel, combined with arsenic, antimony and sulphur, which would be considered valuable if occurring alone, but are not paid for under present conditions, since they are difficult to separate and refine.
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  • The cobalt silver ores are found mainly in Huronian conglomerate, but also in older Keewatin rocks and younger diabase, and the silverbearing region, which at first included only a few square miles, is found to extend 25 m.
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  • Up to the present the most important mineral product of Ontario is nickel, which is mined only in the neighbourhood of Sudbury, where the ores occur in very large deposits, which in 1905 produced 95 0 3 tons, more than half of the world's supply of the metal.
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  • With the nickel copper is always found, and copper ores are worked on their own account in a few localities, such as Bruce mines.
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  • Iron ores have been discovered in many places in connexion with the "iron formation" of the Keewatin, but nowhere in amounts comparable with those of the same formation in Michigan and Minnesota.
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  • Glaze and Glass.From almost the beginning of the prehistoric age there are glazed pottery beads found in the graves: and glazing on amulets of quartz or other stones begins in the middle of the prehistoric. Apparently then glazing went together with the working of the copper ores, and probably accidental slags in the smelting gave the first idea of using glaze intentionally.
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  • Patches of stunted jungle here and there diversify their rugged and barren aspect; but they abound in minerals, especially copper and iron ores.
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  • In the intra-andine depression, between the East and West Cordilleras, recent deposits with plant remains occur near Loja, and to the north-east of Cuenca is a sandstone containing mercury ores, somewhat similar to that of Peru.
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  • Iron ores and lead are credited to several provinces, and platinum has been found in Esmeraldas, where emerald mines have been worked ever since the Spanish conquest.
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  • This special alloy does not occur in any known iron ores, but is invariably found in meteoric iron.
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  • Lower Palaeozoic strata lap up on to the crystalline rocks on all sides of the mountain group. The region is rich in magnetic iron ores, which though mined for many years are not yet fully developed.
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  • Putting aside salt, which has been already treated, the chief mining resources of India at the present day are the coal mines, the gold mines, the petroleum oil-fields, the ruby mines, manganese deposits, mica mines in Bengal, and the tin ores and jade of Burma.
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  • The principal sources of iron-stone at present are the Madras ores, chiefly at Salem, the Chanda ores in the Central Provinces, and the ores obtained at and near Raniganj in Bengal.
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  • The process adopted for the Canadian ores, which are poor in copper and nickel, consists in a preliminary roasting in heaps and smelting in a blast furnace in order to obtain a matte, which is then further smelted with a siliceous flux for a rich matte.
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  • Chalcopyrite is of wide distribution and is the commonest of the ores of copper.
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  • At Rammelsberg in the Harz it forms a bed in argillaceous schist, and at Mansfeld in Thuringia it occurs in the Kupferschiefer with ores of nickel and cobalt.
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  • The iron deposits are very extensive, and the ores consist of red haematites, magnetites, titanic, chrome and manganese irons.
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  • The Hartville ores are remarkable for their high grade and purity, running from 60 to 70% metallic iron, with 22 to 5% silica, and only traces of sulphur and phosphorus.
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  • The iron ore from this district obtained the grand prize at the World's Fair held in Chicago in 1893, in competition with iron ores from all parts of the world.
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  • A day's labour in mines and in works for the reduction of ores is limited to eight hours except in cases of emergency where life or property is in imminent danger.
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  • Traces of mineral oil, iron ores, copper, zinc and antimony have been found, but the wealth of North Borneo still lies mainly in its jungle produce.
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  • The industry waned rapidly toward the middle of the 19th century, but was renewed upon the discovery of the high-grade ores in the S.V.
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  • The city's industrial establishments include smelting works and a large number of reduction works, among which are some of the largest and most important in the republic. It was here that Bartolome de Medina discovered the "patio" process of reducing silver ores with quicksilver in 1 557, and his old hacienda de beneficio is still to be seen.
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  • In the exploitation of the last there have been three periods: that before the discovery of the lead-carbonate silver ores of Leadville in 1879, in which period gold-mining was predominant; the succeeding years until 1894, in which silver-mining was predominant; and the period since 1894, in which gold has attained an overwhelming primacy.
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  • Lead products declined with silver, but a large output of low ores has continued at Leadville, and in 1905 the product was valued at $5,111,570, and in 1906 at $5,933,829.
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  • In addition, iron ores (almost all brown hematite) occur abundantly, and all material for making steel of excellent quality.
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  • Of much more importance are the manganiferous and the silver manganiferous ores, which are much the richest of the country.
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  • Their product trebled from 1889 to 1903; and in 1907 the output of manganiferous ores amounted to 99,711 tons, valued at $251,207.
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  • The cyanide process, introduced about 1890, is now one of the most important factors in the utilization of low-grade and refractory gold and silver ores.
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  • Of the total product in 1905 more than four-fifths were represented by the smelting of lead, copper and zinc ores, the manufacture of iron and steel, the production of coke, and the refining of petroleum.
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  • A small amount of lead is produced incidentally to the mining of zinc, being derived from mixed lead and zinc ores.
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  • Iron ores are widely distributed, but have not been developed; graphite is mined in Colfax county; mica in Taos county, and to a small extent in Rio Arriba county; marble is quarried in Otero county and sandstone in Bernalillo, Colfax and San Miguel counties.
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  • Copper is widely distributed in nature, occurring in most soils, ferruginous mineral waters, and ores.
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  • The principal ores of copper are the oxides cuprite and melaconite, the carbonates malachite and chessylite, the basic chloride atacamite, the silicate chrysocolla, the sulphides chalcocite, chalcopyrite, erubescite and tetrahedrite.
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  • Copper pyrites, or chalcopyrite, contains 34.6% of copper when pure; but many of the ores, such as those worked specially by wet processes on account of the presence of a large proportion of iron sulphide, contain less than 5% of copper.
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  • Cornish ores are almost entirely pyritic; and indeed it is from such ores that by far the largest proportion of copper is extracted throughout the world.
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  • Copper is obtained from its ores by three principal methods, which may be denominated - (r) the pyro-metallurgical or dry method, (2) the hydro-metallurgical or wet method, and (3) the electro-metallurgical method.
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  • The methods of working vary according to the nature of the ores treated and local circumstances.
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  • The dry method, or ordinary smelting, cannot be profitably practised with ores containing less than 4% of copper, for which and for still poorer ores the wet process is preferred.
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  • Since all sulphuretted copper ores (and these are of the most economic importance) are invariably contaminated with arsenic and antimony, it is necessary to eliminate these impurities, as far as possible, at a very early stage.
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  • Roasted ores may be smelted in reverberatory furnaces (English process), or in blast-furnaces (German or Swedish process).
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  • The " American process " or " Pyritic smelting " consists in the direct smelting of raw ores to matte in blast furnaces.
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  • The " AngloGerman Process " is a combination of the two preceding, and consists in smelting the calcined ores in shaft furnaces, concentrating the matte in reverberatory furnaces, and smelting to coarse-metal in either.
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  • Shaft furnaces are in use for ores rich in sulphur, and where it is desirable to convert the waste gases into sulphuric acid.
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  • Reverberatory roasting does not admit of the utilization of the waste gases, and requires fine ores and much labour and fuel; it has, however, the advantage of being rapid.
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  • Muffle furnaces are suitable for fine ores which are liable to decrepitate or sinter.
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  • Reverberatory furnaces of three types are employed in calcining copper ores: (I) fixed furnaces, with either hand or mechanical rabbling; (2) furnaces with movable beds; (3) furnaces with rotating working chambers.
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  • Shaft calcining furnaces are available for fine ores and permit the recovery of the sulphur.
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  • The M`Dougall-Herreshoff, working on ores of over 30% of sulphur, requires no fuel; but in furnaces of the reverberatory type fuel must be used, as an excess of air enters through the slotted sides and the hinged doors which open and shut frequently to permit of the passage of the rakes.
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  • 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.
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  • To-day more than eight-tenths of the copper ores of the world are reduced to impure copper bars or to fine copper at the mines; and where the character of the ore permits, the cupola furnace is found more economical in both fuel and labour than the reverberatory.
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  • In America the usual method is to roast ores or concentrates so that the matte yielded by either the reverberatory or cupola furnace will run from 45 to 50% in copper, and then to transfer to the Bessemer converter, which blows it up to 99%.
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  • Blast furnaces of large size, built of brick, have been constructed for treating the richest and more silicious ores of Rio Tinto, and the Rio Tinto Company has introduced converters at the mine.
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  • - As soon as the pneumatic method of decarburizing pig iron was accepted as practicable, experiments were made with a view to Bessemerizing copper ores and mattes.
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  • One of the earliest and most exhaustive series of experiments was made on Rio Tinto ores at the John Brown works by John Hollway, with the aim of both smelting the ore and concentrating the matte in the same furnace, by the heat evolved through the oxidation of their sulphur and iron.
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  • But considerable progress has been made in smelting highly sulphuretted ores by the heat of their own oxidizable constituents.
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  • When, however, a hot blast is used on highly sulphuretted copper ores, a concentration of 8 of ore into i of matte is obtained, with a consumption of less than one-third the fuel which would be consumed in smelting the charge had the ore been previously calcined.
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  • Austin, of Denver, Colorado, and both at Leadville and Silverton raw ores are successfully smelted with as low a fuel consumption as 3 of coke to zoo of charge.
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  • Two types of pyritic smelting may be distinguished: one, in which the operation is solely sustained by the combustion of the sulphur in the ores, without the assistance of fuel or a hot blast; the other in which the operation is accelerated by fuel, or a hot blast, or both.
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  • Thus these ores, as heavily charged with sulphur as those of the Rio Tinto, are speedily reduced by three operations and without roasting, with a saving of 97.6% of the copper, 93.2% of the silver and 93.6% of the gold.
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  • According to Herbert Lang, its most prominent chance of success is in localities where fuel is dear, and the ores contain precious metals and sufficient sulphides and arsenides to render profitable dressing unnecessary.
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  • Wet methods are only employed for low grade ores (under favourable circumstances ore containing from 4 to i% of copper has admitted of economic treatment), and for gold and silver bearing metallurgical products.
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  • The ores of any economic importance contain the copper either as oxide, carbonate, sulphate or sulphide.
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  • Ores in which the copper is present as oxide or carbonate are soluble in sulphuric or hydrochloric acids, ferrous chloride, ferric sulphate, ammoniacal compounds and sodium thiosulphate.
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  • Sulphuric acid may be applied as such on the ores placed in lead, brick, or stone chambers; or as a mixture of sulphur dioxide, nitrous fumes (generated from Chile saltpetre and sulphuric acid), and steam, which permeates the ore resting on the false bottom of a brick chamber.
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  • Hydrochloric acid is applied in the same way as sulphuric acid; it has certain advantages of which the most important is that it does not admit the formation of basic salts; its chief disadvantage is that it dissolves the oxides of iron, and accordingly must not be used for highly ferriferous ores.
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  • The advantage of this method rests chiefly on the small amount of iron required; but its disadvantages are that any silver present in the ores goes into solution, the formation of basic salts, and the difficulty of filtering from the iron oxides.
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  • It is not used in the treatment of ores, but finds application in the case of calcined argentiferous lead and copper mattes.
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  • Ores in which the copper is present as sulphate are directly lixiviated and treated with iron.
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  • The wet extraction of metallic copper from ores in which it occurs as the sulphide, may be considered to involve the following operations: (r) conversion of the copper into a soluble form, (2) dissolving out the soluble copper salt, (3) the precipitation of the copper.
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  • Calcination is only advisable for ores which contain relatively much iron pyrites and little copper pyrites.
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  • The conversion of copper sulphide into the chlorides may be accomplished by calcining with common salt, or by treating the ores with ferrous chloride and hydrochloric acid or with ferric chloride.
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  • The sulphate, oxide or chlorides, which are obtained from the sulphuretted ores, are lixiviated and the metal precipitated fn the same manner as we have previously described.
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  • Great Britain, though she had made half the world's copper in 1830, held second place in 1860, making from native ores 15,968 tons; in 190o her production was 777 tons, and in 1907, 711 tons.
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  • Copper carbonates are of wide occurrence in the mineral kingdom, and constitute the valuable ores malachite and azurite.
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  • These figures include pig-iron produced from foreign ores.
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  • Metals were obtained from the ores as follows: The total number of persons employed in and about all the mines of the United Kingdom in 1901 was 839,178, and in 1909 I,126,372.
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  • The amount of pig-iron obtained found its minimum, during the period 1890-1910, of 6,976,990 tons in 1893, and its maximum of 10,183,860 in 1906, and in 1905 the quantity produced from foreign ores (4,847,899 tons) for the first time exceeded that produced from British ores (4,760,187).
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  • In the vicinity there are the most important deposits of zinc and lead in the state, and the city derives its name from the deposits of sulphide of lead (galena), which were the first worked about here; below the galena is a zone of zinc carbonate (or smithsonite) ores, which was the main zone worked between 1860 and 1890; still lower is a zone of blende, or zinc sulphide, now the principal source of the mineral wealth of the region.
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  • The iron-mining industry is of high importance, the output of iron ore forming by far the largest item in the total output of ores and minerals.
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  • The percentage of iron in the ore is high, as much as 66% in the Kirunavara-Luossavara ore; and little less in that of Grangesberg; this far exceeds other European ores, though it is equalled by some in America.
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  • Nineteen of the 54 steamers belonged to a subsidized national line whose West Coast service once extended to San Francisco, California, and a large part of the others belongs to a Lota coal-mining and copper-smelting company which employs them in carrying coal to the northern ports and bringing back, metallic ores for smelting.
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  • The principal exports are gold, silver, copper (bars, regulus and ores), cobalt and its ores, lead and its ores, vanadium ores, manganese, coal, nitrate of soda, borate of lime, iodine, sulphur, wheat and guano.
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  • The development of the coal deposits in the provinces of Concepcion and Arauco has made possible other industries besides those of smelting mineral ores, and numerous small manufacturing establishments have resulted, especially in Santiago, Valparaiso, Copiapo and other places where no permanent water power exists.
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  • Manganese ores are mined in Atacama and Coquimbo, and their export is large.
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  • In silver and copper mining the naarc (8 oz.) is commonly used in describing the richness of the ores.
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  • As the rentf and royalties, excepting those on the turquoise mines, amount to about one-fifth of the net proceeds, it may be estimated that th value of the annual output does not exceed 50,000, while thi intrinsic value of the ores, particularly those of lead, iron, cohali and nickel, which have not yet been touched can be estimated al millions.
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  • The richest deposits of nickel, cobalt and antimony ores are also situated in localities where there is little water and the nearest useful fuel some hundred miles away.
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  • It is the natural outlet for the commerce of some of the richest parts of Honduras, Nicaragua and Salvador; and during the 19th century it exported large quantities of gold, silver and other ores, although its progress was retarded by the delay in constructing a transcontinental railway from Puerto Cortes.
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  • It usually occurs as lamellar or glanular masses, with a tin-white colour and metallic lustre, in limestone or in mineral veins often in association with ores of silver.
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  • For rich ores the method of roasting the sulphide with metallic iron is sometimes employed; carbon and salt or sodium sulphate being used to slag the iron.
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  • Its imports during the same year amounted to 899,201 tons, including 172,319 tons of grain and other agricultural produce, 156,620 tons of firewood, 145,255 tons of pig-iron and manufactured iron and steel, 47,201 tons of iron ore, 121,168 tons of copper, -silver, lead, tin and nickel with their ores and alloys, 63,009 tons of zinc, its ores and alloys, 41,029 tons of sulphur ore, phosphates and other raw material for the chemical trade.
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  • Important mines of gold and silver, considerable deposits of wolframite, valuable ores of molybdenum and vanadium, and quarries of onyx marble, are also worked.
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  • These actions are of extreme importance in nature, as their continuation results in the enormous deposits of bog-iron ore, ochre, and - since Molisch has shown that the iron can be replaced by manganese in some bacteria - of manganese ores.
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  • Copper, mercury, and iron ores, as also pure copper, ochre and sulphur, are found in the peninsula.
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  • High grade copper ores have been produced in the Seven Devils and Washington districts of Washington county; there are deposits, little developed up to 1906, in Lemhi county (which was almost inaccessible by railway) and in Bannock county; the copper mined in 1905 was valued at $1,134,846, and in 1907, according to state reports, at $2,241,177, of which about two-thirds was the output of the Cceur d'Alene district in Shoshone county.
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  • Among the exports are coffee, cacao, dyewoods, hides, skins, and copper ores.
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  • Iron ores are found at Krusnahora and Nucic, and the principal foundries are round Kladno and Kdnigshof.
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  • The Altai proper is rich in silver, copper, lead and zinc ores, while in the Kuznetsk Ala-tau, gold, iron and coal are the chief mineral resources.
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  • The Kuznetsk Ala-tau mines are only now beginning to be explored, while the copper, and perhaps also the silver, ores of the Altai proper were worked by the mysterious prehistoric race of the Chudes at a time when the use of iron was not yet known.
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  • The ores of the Altai proper nearly always appear in irregular veins, containing silver, lead, copper and gold - sometimes all together, - and they are, or were, worked chiefly by Zmeinogorsk (or Zmeiev), Zyryanovsk, Ust-Kamenogorsk and Riddersk (abandoned in 1861).
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  • The northern, or Salair, mining region is rich in silver ores, and the mine of this:name used formerly to yield up to 93,300 oz.
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  • In a restricted sense the term assaying is applied in metallurgy to the determination of the amount of gold or silver in ores or alloys; in this article, however, it will be used in a wider technical signification, and will include a description of the methods for the quantitative determination of those elements in ores which affect their value in metallurgical operations.
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  • Ores containing gold or silver are almost invariably assayed in the dry way; that is, by fusion with appropriate fluxes and ultimate separation of the elements in the metallic form.
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  • The crucible method is generally used for ores containing gold in small amounts and for certain classes of silver ores.
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  • The .amount of ore taken for assay is generally one-half "A.T.," but in very low-grade ores one, two, and sometimes even four "A.T.s" are used.
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  • In ores containing much copper, this metal is largely concentrated in the lead button, making it hard, and necessitating repeated scorifications and, in some cases, a preliminary removal of the copper by solution of the ore in nitric acid.
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  • Ores containing much arsenic or sulphur are generally roasted at a low heat and the assay is made on the roasted material.
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  • The "dry" or fire assay for lead is largely used for the valuation of lead ores, although it is being gradually replaced by volumetric methods.
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  • The most accurate method for the determination of lead in ores is the gravimetric method, in which it is weighed as lead sulphate after the various impurities have been separated.
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  • Nearly all lead ores contain more or less sulphur; and as in the process of solution in nitric acid this is oxidized to sulphuric acid which unites with the lead to form the very insoluble lead sulphate, it is simpler to add sulphuric acid to convert all the lead into sulphate and then evaporate until the nitric acid is expelled.
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  • There are several volumetric methods for assaying lead ores, but the best known is that based on the precipitation of lead by ammonium molybdate in an acetic acid solution.
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  • ==Zinc== Chemically the ores of zinc consist of the silicates, carbonates, oxides, and sulphides of zinc associated with other metals, some of which complicate the methods of assay.
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  • This method is modified in practice by the character of the ores, carbonates and silicates free from sulphides being decomposed by hydrochloric acid, with the addition of a little nitric acid.
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  • The fire assay for copper ores was abandoned years ago and the electrolytic method took its place; this in turn is now largely replaced by volumetric methods.
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  • The element is a constituent of many mineral sulphides, some of which are of sufficiently frequent occurrence to rank as ores of silver.
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  • From the metallurgical point of view, silver ores may be classified as real silver ores and argentiferous ores.
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  • Metalliferous products containing silver arise in many operations; the chief products which may yield silver economically are copper and lead mattes, burnt argentiferous pyrites and certain drosses and scums. Argentiferous ores consist of silver-bearing base-metal minerals and gangue.
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  • Lead and copper ores, carrying silver in some form or other, are the leading representatives.
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  • Often it is more profitable to smelt real silver ores with argentiferous ores than to mill them, the greater cost being more than balanced by the increased yield.
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  • The yield in silver is low unless the ores are exceptionally free-milling; the bullion produced is high-grade, as refractory silver minerals are hardly attacked.
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  • The process is suited to easy ores and a region where the climate is warm and dry, and horseor mule-power, labour and quicksilver are cheaper than fuel and water.
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  • The ores may contain a larger proportion of sulphides and complex silver minerals than with the Patio process and still give a satisfactory extraction.
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  • The Francke-Tina process, named from Francke, German consul at Bolivia, and tina, the wooden vat in which the process is carried out, was developed in Bolivia for the treatment of refractory ores rich in zinc blende and tetrahedrite (fahl-ore).
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  • Ores suited for amalgamation can, as a rule, be successfully leached.
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  • Sodium chloride, characteristic of the Augustin process in which the ores, after a chloridizing roast, were extracted with brine, and the silver precipitated by copper, has almost wholly fallen into disuse; and potassium cyanide, which has become a very important solvent for finely divided gold, is rarely used in leaching silver ores.
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  • Of mineral ores the most important are iron, zinc and copper.
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  • The manufacture of iron in New Jersey dates from 1674, when the metal was reduced from its ores near Shrewsbury, Monmouth county.
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  • Magnetic ores, found chiefly in Morris, Passaic and Warren counties, form the basis of the present industry.
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  • Bog ores were mined until about 1840; since that date they have had no market.
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  • These mountains are still the chief source of copper, but the ores, chiefly cuprite, malachite and chrysocolla, are also found in various parts of the Piedmont region.
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  • It is associated with beds of lava and volcanic ash, some of which contain copper ores.
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  • The coal is present in such vast amount as to offer the possibility of very economical working of the abundant iron ores of Australia.
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  • The zinc ores associated with the silver-lead long lay unutilized, as the problem of their separation from the associated rhodonite has only recently been overcome.
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  • The copper lodes of New South Wales contain ores of a much higher grade than those of many well-known mines .worked at a profit in other parts of the world, and, with a fair price for copper, the production largely increases.
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  • The iron ores of the Coal Measures have given rise to great manufactures of steel, from cutlery to machinery and armour-plates.
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  • Ores of good quality are now known to be quite generally distributed throughout the state.
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  • In 1908 the richest producers of gold were Salt Lake (60,872.63 oz.), Juab (58,679.17 oz.) and Tooele (41,969.96 oz.) counties, which produced about nine-tenths of the total for the state; in Salt Lake and Juab counties the principal source was copper ore, but in Tooele county almost all the gold was from siliceous ores.
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  • (of which more than two-thirds was from copper ores) were from Juab county; 2,463,735 oz.
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  • (all but 9586 oz., which were from lead zinc ore, being from lead ores) were from Summit and Wasatch counties; 1,561,983 oz.
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  • The principal source of the silver was the lead ores mined, from which in 1908 about two-thirds of the total of the silver was secured.
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  • In 1908 more than two-thirds of the total output was from the low-grade porphyry ores mined at Newhouse, Beaver county, and at Bingham, Salt Lake county.
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  • Native silver as well as silver ores exist around Thunder Bay, native copper was formerly worked on Isle Royal, and rich copper mines are worked on the south shore, while nickel abounds in the country north of the lake.
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  • Trade has enormously expanded; new centres of commerce have sprung up in spots which formerly were silent jungles; new staples of trade, such as tea and jute, have rapidly attained importance; and the coalfields and iron ores have opened up prospects of a new and splendid era in the internal development of the country.
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  • The lead ores are galena and carbonate; the zinc ores, calamine, smithsonite and blende.
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  • Both the St Francois and Jasper ores yield from 70 to 75% of metal in final product, and assay even higher.
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  • In the Joplin mining region a considerable amount of ores is smelted, but the bulk of the ores is sent into Kansas for smelting.
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  • The exports consist principally of coal and iron from collieries and ironworks in the neighbourhood; and the imports of timber, ores and general goods.
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  • Copper ores are known to be quite widely distributed in the mountain districts, but there has been little work on any except some in Josephine and Grant counties; in 1908 the state's output amounted to 291,377 lb of copper.
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  • The gas produced in the burning of sulphur ores, when issuing from the burner, holds in mechanical suspension a considerable quantity of" flue-dust,"which must be removed as far as is practicable before the gas is subjected to further treatment.
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  • The principal ores are galena, sphalerite or zinc blende and smithsonite or zinc carbonate, which is locally called "dry bone" and which was the first zinc ore mined in the state.
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  • Although iron occurs only sparingly in the free state, the abundance of ores from which it may be readily obtained led to its application in the arts at a very remote period.
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  • The earlier sources of the ores appear to have been in India; the Greeks, however, obtained it from the Chalybes, who dwelt on the south coast of the Black Sea; and the Romans, besides drawing from these deposits, also exploited Spain, Elba and the province of Noricum.
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  • The principal iron ores are the oxides and carbonates, and these readily yield the metal by smelting with carbon.
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  • Ferric oxide or iron sesquioxide, Fe203, constitutes the valuable ores red haematite and specular iron; the minerals brown haematite or limonite, and gothite and also iron rust are hydrated forms. It is obtained as a steel-grey crystalline powder by igniting the oxide or any ferric salt containing a volatile acid.
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  • Silver, lead and iron ores occur in several localities; but the want of fuel is an obstacle to their exploitation.
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  • From the hinterland comes mostly raw produce such as grain, drugs, wool, silk, ores and also carpets.
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  • As its name (Ore Mountains) indicates, it is famous for its mineral ores.
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  • Minerals which were not mined commercially in 1902 include asbestos, which occurs in Spartanburg and Pickens counties; fullers'-earth; graphite in Spartanburg and Greenville counties; iron ores in the north and north-west portions of the state; iron pyrites in Spartanburg and York counties; talc, bismuth, ochre, pyrites, ' galena, brown coal, malachite, phosphate of lead and barytes.
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  • The older rocks are in many places peculiarly rich in metalliferous ores of all kinds.
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  • Amongst them may be mentioned the silver-bearing lead ores of Erzgebirge and of P?ibram in Bohemia; the iron ores of Styria and Bukovina; and the iron, copper, cobalt and nickel of the districts of Zips and GSmor.
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  • Native arsenic occurs usually in metalliferous veins in association with ores of antimony, silver, &c.; the silver mines of Freiberg in Saxony, St Andreasberg in the Harz, and Chanarcillo in Chile being well-known localities.
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  • In 1830 an attempt, finally unsuccessful mainly owing to the lack of fuel, was made to smelt iron from the ores found in the vicinity.
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  • The metallic ores of the Pyrenees are not in general of much importance, though there are considerable iron mines at Vic de Sos in Ariege and at the foot of Canigou in Pyrenees-Orientales.
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  • Iron ores (60 to 70% of iron), copper ores, colours, brown coal, graphite, slate, and lithographic stone are obtained - nearly 2,000,000 tons of iron ore annually.
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  • The minerals of most commercial importance are coal, iron ores, copper ores, marble and phosphate rock.
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  • After the close of the Civil War (1865) the iron resources of the state attracted renewed attention, particularly the brown and red hematites, and large and modern furnaces were erected in the Chattanooga district to reduce these ores.
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  • Where the operation is simply one of fusion, as in the ironfounder's cupola, in which there is no very great change in volume in the materials on their descent to the tuyeres, the stack is nearly or quite straight-sided; but when, as is the case with the smelting of iron ores with limestone flux, a large proportion of volatile matter has to be removed in the process, a wall of varying inclination is used, so that the body of the furnace is formed of two dissimilar truncated cones, joined by their bases, the lower one passing downwards into a short, nearly cylindrical, position.
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  • 2, 3 and 4 represent a reverberatory furnace such as is used for the fusion of copper ores for regulus, and may be taken as gener ally representing its class.
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  • The former have a very extended application in many branches of industry, being used by both founders and smelters in the fusion of metals; in the concentration of poor metallic compounds by fusion into regulus; in the reduction of lead and tin ores; for refining copper and silver; and for making malleable iron by the puddling processes and welding.
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  • These are known as muffle or chamber furnaces; and by supposing the crucibles or retorts to represent similar chambers of only temporary duration, the ordinary pot melting air furnaces, and those for the reduction of zinc ores or the manufacture of coal gas, may be included in the same category.
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  • This method has received considerable extension, notably in furnace-smelting of iron ores containing manganese, where the entire hearth is often completely water-cased, and in some lead furnaces where no firebrick lining is used, the lower part of the furnace stack being a mere double iron box cooled by water sufficiently to keep a coating of slag adhering to the inner shell which prevents the metal from being acted upon.
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  • As calciners they are used in tin mines and for the chlorination of silver ores.
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