Basic Mining Methods (back to resources)

Mining is done by open pit methods on the surface or by underground methods requiring tramming and hoisting of the ore to the surface. Open pit mining includes excavating low-grade waste rock to a disposal dump area and haulage of ore-grade material to a processing area. Underground mining requires access to higher grade ore by way of a vertical shaft or decline to the deeper mineralization. The ore is delivered to the processing area by haulage to the shaft in underground tunnels (drifts) and hoisting ore to surface in a shaft. All of this material is drilled, blasted, and transported by truck, tram, or conveyor.

Processing is done by heap leaching or milling methods. Low operating cost heap leaching methods are used to recover precious metals from lower grade material that contains recoverable metal at a relatively coarse size using crushing only. Milling of ore involves both crushing and grinding of the ore to a fine size in order to liberate the mineral and metal values so they can be recovered by gravity and leaching methods to a concentrated or relatively pure metal product. The waste material (called tailings), is disposed of and impounded in a disposal area.

Both mining method and processing method will be determined by economics of recovering the precious metals. The economics, or feasibility of a project, is determined from the location and grade of the ore body and from the results of test work used to define the optimum metal recoverable from the ore.