Engineering and Mining Journal - Whether the market is copper, gold, nickel, iron ore, lead/zinc, PGM, diamonds or other commodities, E&MJ takes the lead in projecting trends, following development and reporting on the most efficient operating pr
Issue link: https://emj.epubxp.com/i/115330
NARROW VEIN Niche Machines for Narrow-Vein Mining While the world's major mines focus on bulk extraction, narrow-vein deposits demand a different approach—and different equipment. E&MJ; looks at some of the possibilities. By Simon Walker, European Editor Boart Longyear reports that demand for its StopeMate drill has been increasing as more narrow-vein mines come on stream. It also offers the easily maneuverable StopeMaster rig, designed for bulk mining applications. Go back a hundred years—150 certainly— and most of the world's mineral production came from narrow-vein deposits. Processing technology had not yet matured sufficiently to be able to handle bulk materials, flotation had still to be adopted for sulphide treatment and the introduction of the industrial-scale cyanidation processes that are today taken for granted as the prime precious-metals recovery route was still in the future. Mines had traditionally operated in a narrow-vein environment, even if veins ran en echelon, simply because the technology of the day would not allow anything more extensive. And, of course, waste-rock handling was minimized as mining was highly selective, keeping profitless dilution at rock-bottom. The discovery of massive sulphide deposits, and gold plays such as the AJ near Juneau in Alaska—where block caving 32 E&MJ; • MARCH 2013 was invented—changed all that, with new stoping methods being developed to extract them. Throughout the 20th century the focus tightened increasingly on higher-tonnage, lower-grade deposits as economies of scale in mining and processing broadened the viability range for orebodies. Add to that the realization that the epithermal vein systems that had been worked in the past were merely a near-surface expression of larger bulk resources below, and it is easy to see why the emphasis shifted away from narrow-vein opportunities. Nonetheless, smaller mines worldwide continued to run on a more selective basis, with the major manufacturers keeping them supplied with equipment that was suitable for their constricted mine infrastructure. Looking back to the late 1980s, Tamrock, Secoma, Atlas Copco and several other suppliers all had drill rigs that were designed specifically for small-scale development; Tamrock's MiniMatic and Secoma's Quasar were two examples of single-boom jumbos targeted at the smallmine market. In addition, the introduction of rubbertired jumbos to replace hand-held development drifters forced a re-think in terms of mucking technology. Tires and rails do not really mix in development headings, so small-capacity LHDs supplanted railmounted Eimco loaders and wagons. The shift from pneumatic to hydraulic drilling also brought changes to the narrowvein mining market, in that compressed-air ranges became less important within the mine infrastructure. Conversely, having more diesel-powered equipment in the close confines of a vein-mining system brought new ventilation challenges, while few narrow-vein mines today rely solely on shaft access; diesel vehicles need ramp access, as well as underground service facilities. The high gold price in recent years has led to a resurgence in interest in small, limited-resource deposits that can be mined profitably using narrow-vein techniques. Lake Shore Gold's Bell Creek mine, near Timmins, Ontario (Reviewed in the February edition of E&MJ;, pp.28–34), is one such, with a tightly constrained ore zone that demands both small development equipment and close sub-level spacing for longhole stope drilling. A 2-yd3 LHD takes broken rock from the development ends and stopes to the transfer point on the main ramp, from where it is handled by larger loaders and mine trucks. And, even though the orebody appears to widen as it gets deeper, it is unlikely to warrant the use of much larger-scale equipment—apart from ramp haulage—for the foreseeable future. Production Rigs for Tight Spaces According to the company's global product manager, John Nielson, Boart Longyear's StopeMaster and StopeMate rigs are ideal for the tight and narrow spaces typically seen in underground mining operations. As a result, the company is seeing the demand www.e-mj.com