Zinc ore

“ Zinc (Zn) .—This metal is found in considerable abundance, but never occurs in the pure metallic state, but in combination with other substances, chiefly as sulphide in zinc blende, as carbonate in calamine, and as the silicate in the kieselzinc ore; also, with sulphuric acid, the "vitriol of zinc."
Zinc is of a bluish-white color and metallic lustre, is crystalline and brittle when heated 400°F., but malleable and ductile between 200° and 300°. It will not oxidize in dry air, but tarnishes if exposed to air containing moisture, first becomes grey, and then passes into the white carbonate. ”

“ The Zinc adheres to the fore-part of the furnace preferably to any other, because that being the thinnest is therefore the coolest: and, in order further to promote its fixing on this part, they take care to keep the thin stone plates cool during the operation, by throwing water on them.
Hence it appears, that Zinc is not extracted from its ore by fusion and the precipitation of a Regulus, like other metallic substances. This is owing to the great volatility of our semi-metal, which cannot, without subliming, bear the degree of fire necessary to melt its ore. ”

“ The magnetic concentrates contain enough zinc to be well adapted to the manufacture of zinc oxide. Magnetic concentration is also applied in the removal of an excess of iron from partially roasted blende. Neither mechanical non-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. ”

“ Zinc is not generally obtained from a particular ore of its own; but sublimes during the fusion of a mineral, or rather [Pg 118] a confused mass of minerals, that contains this semi-metal together with iron, copper, lead, sulphur, arsenic, and, like all other ores, an unmetallic earth.
Nevertheless, there is a substance which may be considered as the proper ore of zinc, because it contains a pretty large quantity of that semi-metal, a little iron, and an unmetallic earth. It is called Calamine, or Lapis Calaminaris ”

“ On this the success of the operation partly depends, as it is the means of the Copper's preserving its purity and malleability; because the other metallic substances that may be united with the ore of Zinc, or with the Zinc itself, not having the same volatility, cannot be reduced to vapours. If you are apprised that the Calamine, or other ore of Zinc used on this occasion, is contaminated with a mixture of any other metallic matter, you must mingle luting earth with the charcoal-dust and the matter containing the Zinc ”

“ Zinc is abundant in nearly every part of the world. In the United States the best known mines are in the Galena-Joplin District, in Missouri and Kansas, which produce about two-thirds of the home product—mainly from the ore blende, a sulphide. There are also extensive zinc-mining operations in Illinois, New Jersey, and Pennsylvania. ”

“ Zinc ore is obtained chiefly from mines in Cumberland, Wales and the Isle of Man. In 1881 the output reached 35,527 tons, valued at £110,043; in 1891 the output was only 22,216 tons, but its value was £113,445. In 1897 the quantity was 19,278 tons, and the value £69,134; but in 1898 Zinc.the price had risen so that the output of 23,552 tons was worth £117,784. In 1900 the output of 24,675 tons was worth £97,606; and in 1905 that of 23,909 tons was worth £139,806. ”

“ The greatest new factor in the world’s output of zinc will be the Bawdwin mines, in Burma, which within a short time will be equipped to produce about 300,000 tons of ore annually or about 75,000 tons of high-grade zinc concentrates and 100,000 tons of low-grade concentrates or middlings for treatment by the Ganlin process. ”

“ Zinc is not found in a native state. This ore is in the form of an oxide, as it is called. In roasting, certain of the impurities are driven off in gases, and mixing it with charcoal or coke and then applying heat to the confined mass, causes the zinc to melt and finally go off into a gas, as we shall presently see. ”

“ Some manganese is usually present replacing zinc. It is found in the zinc mines at Sterling Hill and Franklin Furnace in Sussex county, New Jersey, where it is associated with franklinite and willemite in crystalline limestone, and is mined as an ore of zinc. Artificial crystals of a white or yellowish colour are not infrequently formed by sublimation in zinc furnaces. ”

“ The many varieties of steel are used in the production of motor vehicles, ships, railroad equipment, pipe and tubing, construction products, containers, appliances, machinery tools, cutlery, and hundreds of other miscellaneous items.
Zinc In 1971, the United States was the third largest producer of zinc ore in the world and the leading producer and consumer of refined zinc. Fifty percent of the total domestic imports of ore and zinc metal in 1971 were supplied by Canada which led the world in ore production. Total domestic slab zinc production in 1971 was 847 thousand short tons. ”

“ The reduction of metallic zinc from its ores is based on the fact that zinc oxide [7] is easily reduced by charcoal at a red heat: ZnO + C [43] = Zn + CO. The zinc thus obtained is in a finely divided state and impure, being mixed with other metals reduced with it, but the greater portion is converted into vapour, from which it easily passes into a liquid or solid state. The reduction and distillation are carried on in earthenware retorts, filled with a mixture of the divided ore and charcoal. ”

“ The ore is low grade, the average recovery of zinc being 1.9 per cent. This horizon has been the most important source of ore. The third and lowest horizon, as yet little exploited, contains disseminated ores. Thirty mills were busy in the Joplin district in 1918. The Athletic Mining & Smelting Co. was the largest producer, operating the Athletic mine, at Duenweg, the Bertha A., at Webb City, and Mutual mine, at Oronogo. Miami Zinc Syndicate, affiliated with the Butte & Superior and American Zinc, Lead & Smelting Co.; the Commerce Mining & Royalty Co. ”

“ The heat evolved reduces the ore and distills the zinc, and the zinc fumes are condensed in the condensing chamber, precisely as in the present method of zinc making, with this important exception that, aside from the reaction produced by heating carbon in the presence of zinc oxide, the electric current, in passing through the zinc oxide, has a decomposing and disintegrating action upon it, not unlike the effect produced by an electric current in a solution. This action accelerates the reduction, and promotes economy in the process. ”

“ Zinc is incomparably rarer than magnesium, and is only well known because it is transformed from its ores into a metal which finds direct use in many branches of industry.
[7] Ores, when extracted from the earth by the miners, are often enriched by sorting, washing, and other mechanical operations. The sulphurous ores (and likewise others) are then generally roasted. Roasting an ore means heating it to redness in air. The sulphur then burns, and passes off in the form of sulphurous anhydride, SO2, and the metal oxidises. ”

“ We know not what may be found in the lower strata of the soil. There is reason to believe that the main bodies of ore have not yet been hit upon; that they lie deeper, and that we have thus far only been engaged upon the spurs and detached masses. There is also reason to believe that bodies of the ores of zinc exist in the district of the mines, and that copper will be afforded by the lower strata of earth. It is found overlaid by lead-ores in many of the European mines ”

“ In one group, the silver-lead deposits, zinc seems a minor factor, but with depth replaces lead as the predominant metal. Deposits of these complex ores have in recent years become important sources of zinc through recognition of the zinc ores in their oxidized zones, through zinc becoming the dominant metal with increasing depth at many mines, and especially through improvements in methods of concentrating complex ores and extracting metal from the concentrates. ”

“ The chief ore is zinc blende, or sphalerite (see Blende) , which generally contains, in addition to zinc sulphide, small amounts of the sulphides of iron, silver and cadmium. It may also be accompanied by pyrites, galena, arsenides and antimonides, quartz, calcite, dolomite, &c. It is widely distributed, and is particularly abundant in Germany (the Harz, Silesia) , Austro-Hungary, Belgium, the United States and in England (Cumberland, Derbyshire, Cornwall, North Wales) . Second in importance is the carbonate, calamine (q.v.) or zinc spar, which at one time was the principal ore ”

“ When the action becomes sluggish, dilute with an equal bulk of water, and add a weighed piece of zinc rod about 1 inch long and quarter-inch across. Keep up a moderate action by warming till the ore is seen to be completely attacked and the lead precipitated. Decant off the solution, wash once, strip off the lead, wash and weigh the remaining zinc. Dissolve the lead in 5 c.c. of dilute nitric acid, and 5 c.c. of water with the aid of heat. Dilute and transfer to a pint flask; add a slight excess of dilute ammonia, and render faintly acid with acetic acid. ”

“ The Franklin deposits, in New Jersey, consist chiefly of franklinite, willemite and zincite in a gangue of calcite, rhodonite, garnet, pyroxene, magnetite and hornblende. Willemite is separated magnetically from these ores and used to produce a very high-grade spelter free from lead and cadmium and therefore in great demand for certain purposes. The other classes of ore are smelted for the production of zinc white and spiegeleisen. These mines, owned and operated by the New Jersey Zinc Co., have produced more than 1,500,000 tons of zinc in the form of spelter and zinc oxide. ”

“ It is a handsome metal, but little affected by oxygen, and capable of being rolled into thin sheets.
Zinc is found in two different ores: red oxide (ZnO) and zinc blende (ZnS) , from which it can be separated by smelting, in much the same manner as we obtain iron.
Lead constitutes the fifth of the common metals which are preëminently useful. It is found in the sulphide of lead (PbS) , the sulphide being expelled by roasting the ore. It forms numerous compounds, some of which are of great value. ”

“ Zinc ores, in the several varieties of carbonates, silicates, oxide, sulphide and sulphate of zinc, have been found in several of the Australian states but have attracted little attention except in New South Wales, where special efforts are being made successfully to produce a high-grade zinc concentrate from the sulphide ores. ”

“ It is also found at Cave-in-Rock, Gallatin county, Illinois, accompanied by fluor spar; at Drennon's Lick and Millersburgh, in Kentucky; and on New river, at Austinville, in Wythe county, Virginia. At the latter place, it has been worked without interruption for nearly fifty years; and the mines still continue to be wrought. The ore is galena, accompanied by the carbonate of lead, and the earthy oxide of lead; the latter of which is worked in the large way, as is said, to a profit.
Zinc is found in Washington county, Missouri, in considerable quantities ”

“ The ores usually contain both zinc and lead in varying proportions, and sometimes gold, silver, and copper are present. Of the zinc produced in the United States, about 73 per cent is obtained from ores containing zinc as the principal element of value, about 25 per cent from zinc-lead ores, and 2 per cent from copper-zinc and other ores. The average grade of the straight zinc ores is about 2-1⁄2 per cent. ”

“ Reduction is carried out in the Belgian or Silesian process by strongly heating calcined matte with coal in retorts. The zinc as it distils is caught in special condensing receptacles (prolongs) . After distillation is complete the residue is raked out of the muffle and the furnace charged afresh. As zinc ores generally contain much lead, the work-zinc is therefore refined [126] by remelting in a reverberatory furnace, during which process the impurities collect on the zinc as dross and are removed by agitation with sal-ammoniac or magnesium chloride. ”

“ English and French zinc-smelting capacity was expanded during the war, and the industry in these countries is in a strong position. Japan also developed a considerable smelting industry during the war, importing ores from eastern Asia and Australia.
The United States normally smelts and consumes all its large production of zinc ores and does not enter foreign markets to any extent. Small amounts of zinc concentrates are brought in from Mexico and Canada to be smelted in bond. ”

“ They are found in the Mississippi Valley, in Silesia, and in many of the smaller European deposits. They were formerly the leading zinc-producers, and now produce about 45 per cent of the world's total. Zinc ores of the second type consist of veins and replacements related to intrusive rocks, sometimes extending to considerable depths, and of more complex composition. They include most of the deposits of the American Cordilleran region (Butte, Cœur d'Alene, Leadville, etc.) , of Franklin Furnace, of Australia, of Burma, and of many other places. ”

“ It is generally recognized that the purest ores produce the purest metal. 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. Chemical control of the metal purchased is not nearly as common as it should be, and the refining of zinc is at best an imperfect operation. To obtain the metal chemically pure a specially prepared pure oxide or salt of zinc is distilled. ”