COPPER

a very large part of the world’s supply of copper from rg1o onwards came from deposits so low in grade that they could not be worked under the conditions of 1905. the major developments were the enlargement of the scale of operations; reductions in the cost of mining by the introduction of the caving system and steam shovelling; reduction in the cost of milling and increase in the extraction of mineral by the intro- duction of the flotation process; reduction in the cost of smelting by the application of coal-dust firing to reverberatory furnaces and the successful operation of basic-lined converters; and the development of processes for the hydrometallurgical treatment of certain ores and the direct production of refined electrolytic copper. these developments facilitated the exploitation of the ‘ por- phyry ” deposits, which may be described as fine disseminations of copper minerals through large masses of igneous rock. these deposits are large, and occur at or near the surface in substan- tially horizontal positions. fine disseminations of copper had been exploited for many years in the lake superior region, but there the copper occurred in its native form, and the mineralisa- tion was in lodes dipping steeply. previous to 1905 the occur- rence of immense masses of rock, containing about 2% of copper in sulphide form, was known in bingham canyon, utah, at ely, nev., and elsewhere, but it was not believed to be possible to exploit them profitably. the conception of profitable exploita- tion by taking advantage of improved methods and the prosecu- tion of operations on a previously unparalleled scale was due especially to daniel c. jackling (b. 1869), of san francisco. with modern developments it has been found possible to work ores containing little more than 1% of copper. steam shovelling —no detailed description is necessary, for the steam shovels and general methods are substantially the same as in any excavation work. in their application to the min- ing of copper-bearing ore, the latter is broken down in benches, a line of holes being churn-drilled back of the face, charged heavily with an explosive, and the ore blasted down in quantities of many thousands of tons. the steam shovel is moved along a track at the bottom of the bench and picks up the broken ore, transferring it to cars alongside. excessively large boulders are broken up by block-holing and blasting, but the steam shovel can pick up very large pieces, its dipper being up to g cu. yd. in capacity. shovels of 8 cu. yd. capacity weigh 325 tons and dig 300 cu. yd. (place measure) per hour. this method of mining is copieenhagen—copper so cheap per ton of ore that it can be applied economically even when it is necessary to shovel away up to 200 ft. of worthless overburden in order to uncover 100 vertical ft. of ore. the proc- ess of removing the overburden, technically known as stripping, necessarily precedes the actual mining. the laying out of plans for the working of a mine in this way, and the figuring of the various factors, furnish complicated engineering problems. caving.—when the overburden is too thick, or is too thick with relation to the thickness of the ore deposit, mining by the caving system is adopted. in essence this system consists in opening permanent galleries under the ore body. raises to the ore body are then made, and sub-galleries of relatively small size driven into it, with the purpose of so undercutting the ore body that its support by rock pillars is reduced to the minimum. finally the pillars are blasted out, causing the superincumbent ore to settle in a great crushed mass. the crushed ore is then drawn off through chutes, previously prepared, into cars in the main galleries. this operation proceeds through the ore body section by section, the natural surface over the mines settling as the ore is drawn off. there are many modifications of this system of mining, but its application to large flat-lying ore deposits is sub- stantially as above. modifications of the caving system of min- ing are also applicable in many lode mines, when the lodes are of large size. it is a very economical system of mining owing to its reduced requirements for labour, explosives, timber, etc. flotation process.—copper ore as mined in 1925 contained generally only a small percentage of copper mineral, which was obtained by crushing the ore to such fineness as to liberate the mineral particles, and by separating these from the worthless gangue by mechanical processes, commonly performed by wash- ing, in which advantage is taken of the difference in specific gravities. although there had been great improvements in the process of ore dressing, the losses of valuable mineral continued relatively high up to rgro. in the flotation process advantage was taken of the discovery that when ore suspended in water was mixed with a small quantity of certain oils or other agents (the addition of oil being perhaps only 2 lb. per ton of ore), and was then subjected to violent agitation, the copper minerals (if sul- phides) would rise to the surface in the form of a froth, while the worthless gangue would settle to the bottom. separation in this way was possible at relatively low cost, and yielded a far higher percentage of the mineral than the older processes. the improve- ment might be generalised by indicating an extraction of 90%, compared with 65 to 75% previously. in recent years the use of additional chemical agents has developed the process of ‘‘selec- tive flotation,’ whereby minerals of approximately the same specific gravity may be efficiently separated from each other. metallurgy. before tgto the blast furnace and the reverbera- tory furnace were competitive choices for the smelting of copper ore. with the increasing fineness of the ore to be smelted, the leaning began to be definitely in favour of the reverberatory furnace, but with the advent of the dwight-lloyd sinterer, which enables fine ores to be agglomerated cheaply and efficiently, the blast furnace gained a new prestige. with the successful applica-_ tion of coal-dust firing, however, due especially to the work of david h. browne at copper cliff, ont., the reverberatory fur- nace obtained an unquestionable predominance, which it is likely to hold. the modern copper-smelting plant designed for the treatment of fine ore comprises roasting furnaces of the mac- dougall type and very large reverberatory smelting furnaces. before introduction of coal-dust firing, a furnace at anaconda, mont., 19 ft. by 112 ft., smelted 240 tons of charge, with one ton of coal per 43 tons of charge. by the new method a furnace 25 ft. by 144 ft. smelted 650 tons, and one ton of coal smelted seven tons of charge. for the smelting of coarse ore, especially of heavy sulphide, the blast furnace operated on the pyritic or the semi-pyritic principle still holds its place. these furnaces also are constructed of very large size. the anaconda co. at- tained dimensions of 72 in. by 1,044 in. at the tuyeres, but this is exceptional, the blast furnaces at most american works being something like 72 in. by 280 inches. the converting of copper matte in a basic-lined vessel, long a copper hope of copper metallurgists, was accomplished by w. h. pierce and e. a. cappelen-smith at the works of the baltimore copper smelting and rolling co. in 1909-10 the process was introduced in the works of the garfield smelting co. in utah. subsequently it was found that the process was not limited to the pierce-smith horizontal converters, but could be applied to other forms of con- verters, both horizontal and upright. the main advantages of the basic over the acid converter are the decreased cost of lining (one basic lining for 2,500 tons of copper compared with one acid lining for 10 tons), greater air efficiency, ability to convert low- grade matte with a mixture of silicious ore, reduction of inter- mediate products, neatness and cleanliness of plant and decrease in danger from accidents. the basic converters are lined with magnesite. their use became general and they reduced the cost of converting copper matte by more than 50%. the existence of immense ore deposits of the porphyry type, but with the coppet occurring as oxide or chloride which rendered the ore unamenable to mechanical concentration, directed re- newed attention to the hydrometallurgical extraction of the cop- per of such ore. at chuquicamata, chile, lies the world’s great- est known deposit of copper, its development being estimated at about 700,000,000 tons assaying about 2% copper. exploita- tion of this was undertaken by the chile copper co., an american corporation. the copper occurs in the ore as brochantite con- taminated with chlorides. e. a. cappelen-smith devised a proc- ess for the leaching of this ore with sulphuric acid, purification of the solution, and deposition of the copper by electrolysis, using magnetic anodes; in practice, however, anodes of ferro- silicon have been substituted. the copper cathodes are melted and cast into bars of grade equivalent to standard electrolytically refined copper. production in 1924 was at the rate of 212,000,000 ib. per annum. at ajo, ariz., the new cornelia copper co. also produced electrolytic copper directly from ore, from which the copper was first leached by sulphuric acid. hydrometallurgical world’s production of copper' 733 extraction of copper was also applied on a large scale for the treatment of tailings, e.g., by the anaconda copper mining co., and by the calumet and hecla mining co., the latter extracting the native copper by means of ammonia, and precipitating the copper as oxide by distillation, with recovery of the ammonia. a similar process was employed for ore treatment at the kenne- cott mine, in alaska. a later development in copper hydrometallurgy was the leach- ing of copper ore in place, which is being done by the ohio cop- per co. in bingham canyon, utah. the ore broken down by the caving system is flooded with water from the surface. hav- ing dissolved a proportion of the copper the water is drawn off and the copper is precipitated by metallic iron. although the extraction of copper by this method is low in terms of percentage, the cheapness of the method enabled the low-grade ore of this mine to be treated profitably. general economic conditions.—before the world war about 15 cents per lb. was regarded as an average market price for copper. the cost of production to the largest producers was about to cents per lb. with the demand for copper for military purposes the price ran up to about 32 cents per lb. at the end of 1916; but increased production began to show its effect in 1917 and in the latter part of that year the american govt. fixed the price at 234 cents. mining, smelting and refining capacities were rapidly increased, and in 1917 american electrolytic refiners attained a capacity for the production of 2,800,000,000 |b. of copper per annum. the surplus supplies in the hands of the governments at the end of the war led to the greatest accumu- lation of unsold copper in the history of the metal, and a bad economic situation developed which continued into 1921. by 1923 the copper industry had regained normality, but at a price inferior to that of pre-war. production —before the war the world’s production of cop- per had risen to about 1,000,000 metric tons. in 1916-8 there (in metric tous of 2,204-6 lb.) country 1914 1915 1916 1917 1918} 1919 1920 1921 iq22 192 1924 north america :— united states 525,529} 646,212] 881,237] 872,065] 879,026 | 548,677| 576,450) 216,295] 464,459] 684,02 742,997 mexico 36,337] 30,969| 55,128] 47,503] 75,529] 60,491] 45,238] 12,316) 27,073] 54,920] 44,589 canada . 34,027] 47,202 47,985] 50,626 2,693 | 36,106} 35,500) 20,532} 22,952} 36,496 46,274 cuba ok 6,251 8,836 7,81 10,313 12,337 | 9,974{ 6,796] 7,802) 10,694) 10,853 11,560 total north america | 602,144) 733,219] 992,166] 980,507 | 1,019,585 | 655,248] 663,984| 256,945| 525,178] 786,298] 845,420 south america:— bolivia 3,874 5,868 5,150 6,400 6,000 7,000} 9,900] 9,683) 9,212 10,654 7,439 chile 44,665 52,341 71,288] 102,527] 106,914] 79,550] 98,952] 59,239) 129,575] 182,384] 190,380 peru 27,090| 34,72 43,078] 45,176] 44,414] 39,230] 32,982] 33,284) 36,408) 44,166 34,923 venezuela 363 544 1,179 l732 6038 635 ; 720 975 1,066 1,116 total south america 75,992 93,480] 120,695] 155,82 157,936 | 126,445} 141,834) 102,932} 176,170] 238,270| 233,858 europe :— poe ue 3,500 3,500 3,500 3,500 2,500 7647/ 1,585) 4,173] 4,581 4,833 4,051 france 10,067 $82 1,287 1 ,oo! 623 73| 1,559] 2,173! 2,902 8,193 5,000 germany 25,000 25,539 24,796 28,632 15,101 | 15,775] 17,255} 19,000] 17,000 17,000 19,500 yugoslavia 4,443 ,200 5,000 11,200 000! 1,209] 2,436] 3,970} 5,222 6,837 8,145 norway . 2,859 2,826 1,614 1,810 2,856 437 55 5,725] 9,615 8,000 9,900 russia. 31,935 25,881 20,887 16,000 ' oe 7 ak 2,000 2,000 3,300 spain and portugal 26,900 37,100 35,400 40,900 45,900] 35,000] 23,000] 33.200} 36,500 51,815 55,079 sweden 4,692 4,561 3,181 4,540 3,785 | 4,030| 1,627] 1,329 6i 4,700 2,800 total europe 109,399) 103,489) 95,665] 107,583] 76,765] 57,971| 48,018) 69,570] 77,881] 103,378] 107,775 asia:— japan. 70,463, 75,416) 100,635] 108,038] 90,341] 78,443) 67,792] 54,092) 54,126] 63,790) 62,940 other asia ; : : 99 535} 1,161] 1,054 735 1,250 total asia . 70,463} 75,416] 100,635] 108,038] 90,341] 79,439] 68,330) 55,253] 55,180) 64,525] 64,190 australasia 38,667 37,709 39,885 36,564 44,722| 16,441] 26,605] 18,932] 12,478 18,139 14,253 africa . 27,033} 31,300; 39,815} 42,656] 31,064 31,350) 30,580} 38,557} 52,816) 72,948) 104,055 other countries 3,000 3,000 3,000 3,000 3,000 | 4,000 3,000; 3,000) 3,000 3,000 4,000 grand totals 926,698] 1,677,613 : 1,391,861 | 1,434,175 | 1,423,413 | 970,894! 952,351 ar 902,703 1,286,558 | 1,373,551 ‘so far as possible, these statistics are based on blister copper, referred to countries wherein ore originated. 2after 1918, austria only. 734 was an annual production of about 1,400,000 tons. after 1918 production was curtailed for several years, but in 1924 it ap- proached the war-time maximum. important new sources of supply are chile and peru, where american interests control the major part of the production, and the katanga, which is under belgian control. the table on p. 733 shows the world production of copper from i914 to 1924. the consumption of copper greatly increased after 1910, especially in the united states, owing mainly to electrical devel- opment. in the period 1922~4 the american consumption was at the rate of 12-19 lb. per person, compared with 8-og lb. in the a oa = ¥, f_ ac * i916 1917 1918 t1979 year fic, 1.—graph illustrating the production of copper 1914-24. (note. the african production is mainly from the katanga province, belgian congo.) 1914 i91s period 1912-4. corresponding figures for other countries were france, 6-81 and 6-33; germany, 4:40 and 7-01; and great britain, 4°54 and 7-25. bibliography.—e. peters, practice of copper smelting (1911); d. m. levy, afodern copper smelting (1912); if. o. hofman, afetal- lurgy of copper (1914); h. a. megraw, the flotation process (1918); j. r. finlay, cost of mining (1920); r. marsh, jr., steam shovel mining (1920); h. o. hofman and c. r. hayward, metallurgy of copper (1924). see also the lingineering and mining journal. (w. rl. 1)