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Show USED AT BINGHAM Great Low-Grade Producers Break Down Vast Tonnage Each Shot. HOW BOSTON CON, MINES ITS PORPHYRY Caving and Steam Shovel Work Both Used to Disturb the the Resources. The Boston Consolidated owns forty-nine forty-nine acres of Impregnated monzonllc carrying car-rying l.n per cent copper, from which an estimated production of ot!. 000, 000 tons of ore can be derived. In addition to this there arc 107 acres of 1 per cent ore, which may constitute a valuable asset in the future, for although Immense copper cop-per deposits arc being developed In many parts of the world, the exhaustion of ore that can bo now profitably worked with copper selling at 112 cents per pound is proceeding so fast that tho revelation revela-tion of fresh resources by development has no tendency lo depress the price. Whatever may be the fluctuations in copper quotations within the next few years, tho future, counted In decades, must call for the utilisation of ores of lower copper-content than can bo mined today. This will necessitate a higher average price for tho metal, unless modern mod-ern improvements In mining and metallurgy metal-lurgy reduce the cost of trculmcnt equally equal-ly with the average diminution In grade. While the average copper-content of .the ore body deovloped by the Boston Consolidated is' placed at 1.5 per cent, much ore of higher tenor exists, which Is characterized of the more highly fractured frac-tured portions of monzonlte. I'or example, exam-ple, the mon'oulte area exti-nds cast-wnrdly cast-wnrdly into the ground of the Ohio Copper Cop-per company, where the slllciflcatlon has neen still more complete, resulting In greater Irregularities tn the distribution of the metal; that Is, there are zones of higher concentration. U may be observed in passing that the more highly slllelous ores are claimed to yield a larger percentage per-centage of extraction by concentration. The low-grade ores of the Boston Consolidated Con-solidated contain .02o ounces sliver and 0.00o gold per ton. On the basis of VI cents copper and 7fi per cent net recovery upon copper and fU per cunt on gold and silver, these ores would yield a gross return of $3.07 per ton, and it is safo to say that the total cost of operation will tall below 'J per ton. The conditions presented by the mou-zonlle mou-zonlle ore body in the territory of the Boston Consolidated have Id to a mining min-ing practice nt variance with that adopted adopt-ed by its neighbor. Both caving and steam-shovel work are utilized, but with fundamental differences. Tho open-cast work Is conducted in benches of moderate mod-erate height, fifty feet being the elevation eleva-tion of bank aimed at; this, however, is subject to considerable variation arising from surface Irregularities. The rock is shattered by blasts in deep holes bored by a Keystone drill. The So. 2 drill Is used, and the holes aro cased with six-inch six-inch well casing. The holes aro drilled twenty-five feet from the edge of the bank, so that with each blast a cube of material approximately twenty-five by twenty-five by fifty feet, or 1158 cubic yards, Is shaken. The bottom of the hole is first "sprung." that is, chambered, cham-bered, with a charge of fifty pounds of dynamite; a large charge of Trojan powder, pow-der, consisting of 500 to 600 pounds Is then introduced nnd exploded electrically with 6X caps. The Trojan poyder Is said to bo particularly well adapted to this work; It Is quite insensible to ordinary shock, doc not freeze, and Is unaffected by moisture. The .'10 per cent grade of powdor Is employed for bank-blasting. The' cost of drilling the holes Is aald to fall below 00 cents per foot. Including necessary renewals of casing, most of the casing, however, being recovered undamaged un-damaged after each blast. At one time an experiment was made with a hole 120 feet deep; it was blasted, with a charge of four tons of per cent dynamite. dyna-mite. The method of blasting a lower bank, however, is considered more sails-factory. sails-factory. The excavation Is done by Marlon Mar-lon and Vulcan steam shovels of the nlnety-f Jve-ton type with five cubic yard dippers. The company owns four of these machines. The usual crew of engine-men, engine-men, cranemen, firemen and four pitmen is employed. The ore Is loaded upon cars on a narrow-gauge track, and conveyed con-veyed around (he smur of the mountain to the mine bin on a gradient of about 2 per cent. The cost of the ore mined and delivered lo the bin is said to average aver-age 183 cents per ton. The use of a narrow nar-row gauge service railway offers some advantages over the standard gauge employed em-ployed in Bingham canyon. It necessitates loss cutting for tho track, and Is much more flexible. Mining and Scientific Press. |