Exploration Drilling Development

Surface diamond drilling will indicate whether a mineralized zone has sufficient potential to become an orebody. To outline the zone with greater accuracy, and confirm that the mineralization is continuous and the estimates of grade and tonnage are correct, surface work is followed by underground development and detailed definition drilling from the workings. Only then can the developer make plans for production.

Diamond drill holes from surface can only tell part of the story. A mineralized zone may pinch or swell or be irregular, and a large amount of diamond drilling is needed to fill in the information between the first holes the developer drills. Sooner or later, drilling long holes from surface becomes prohibitively expensive, and the mine developer must decide whether to continue exploration from underground. If exploration goes ahead, a suitably sized exploration shaft or an access ramp is driven, allowing crews to get closer to the orebody.

The crews drive drifts and cross-cuts from the shaft or ramp, and drilling areas are excavated at regular intervals to accommodate the underground drills. The mineralized body is then drilled from under ground to get an accurate estimate of grade and tonnage.

Up to this point in the exploration program, the only samples taken from the orehody have been the drill cores. Once underground, however, it is possible to obtain much larger bulk samples of the ore by actual mining. The mineralized material removed during this operation provides a bulk sample for metallurgical testing, first at “bench scale” in a laboratory and ultimately at “pilot scale” in an actual mill. The testing is used to determine the extraction method that will recover the most metal from the ore.