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<br /> <br /> cross-cut ramps from a spiral development ramp in the wall of the <br /> ore block, <br /> k <br />11 <br /> Open Bac <br />Cut Without F1 <br /> The ore block is developed by driving a drift (vein width) <br />along strike of the vein. In many cases, there is already a <br /> drift in position. <br /> Production stoping consists of taking a back cut six to <br /> eight feet high and then mucking it out. The second and third <br /> back cuts are then taken. The broken ore from cuts after the <br /> first cut is not mucked out. but Ieft in place; then miners work <br /> on top of it to drill out successive cuts. Using this method, <br /> three back cuts and sometimes four back cuts can be made from a <br /> single drift access. Depending on the ground conditions and the <br /> size of the stope, the broken ore is removed by an overshot <br /> loader, LHD or remote-controlled LHD. This mining technique is <br /> used effectively for pillar removal and in narrow high grade <br /> veins. <br /> Sublevel Long Hole Stoping <br />Ore blocks ace developed by driving an undercut drift (vein <br />width) along strike of the ore blocks and parallel drift 30 feet <br />in the vein wall on a production or tramming level. These drifts <br />are connected at 30-foot intervals by draw pockets. Sublevels <br />are driven (vein width) at 20 - 25 foot intervals along dip. The <br />sublevels are accessed by cross-cuts from spiral ramps developed <br />between tramming levels. <br />Production stoping consists of connecting sublevels with <br />break raises at the ore block boundaries and longhole drilling <br />down between sublevels. Blastfng is carried out stepwise from <br />bottom to top of the ore block retreating from the ore block <br />boundaries to the sublevel access cross-cuts. There are no areas <br />in the mine currently using this mining technique. <br />MILLING <br />`,y~i~" ~lur r ' ~ Jr <br />Run of mine ore is crushed in a three stage plant, then <br />ground to nominally 75 percent passing 100 mesh in a tool mill and <br />two ball mills. About 60 percent of the gold is recovered from a <br />gravity circuit consisting of jigs, feeding a strake~, strake <br />concentrate feeding a Diester table. The final gold concentrate <br />from the gravity circuit is amalgamated and then retorted into <br />done bullion. Within the grinding circuit is a flash flotation <br />cell which produces highgrade silver-lead-copper concentrate as <br />feed for a lead-copper separation column cell. They primary <br />flotation circuit produces lead and zinc concentrates; lead <br />concentrate is also feed for the lead-copper separation. Final <br />lead concentrate contains about 50 percent lead, about one-half <br />ounce gold and 20 ounces silver per ton. Final. copper <br />concentrate contains about 27 percent copper, about tiro ounces <br />gold and 50 ounces silver per ton. Final zinc concentr~~te <br />- 13 - <br />