Calibre Mining Corp (TSE: CXB) (OTCMKTS: CXBMF) is celebrating a major achievement at Nevada’s Pan Gold Mine.
The gold producer revealed Thursday that the US$7.5-million-dollar expansion of the operation’s heap leach pad has been completed. It took Pan employees and a 45-person contract worker team five months to finish the labour involved. They did so without a single injury, using US$500,000 less than the budget permitted.
“That’s a major achievement on the safety side, and a big positive for the mine,” Calibre’s project manager Dan Ferriter said, “because it contributes to the mine safety record as well.”
Calibre hired the heap leach pad specialist High Mark Construction as the primary contractor for the job. High Mark has been serving Nevada for over 25 years. The company also specializes in tailings dam construction, mine reclamation and other general mine site development work.
A vast 1.6 million square feet of liner has been added, thereby providing the company with an additional four years of mining capacity. Vancouver’s SRK Consulting was responsible for designing the expansion.
As the heap leach pad uses a cyanide solution to extract gold from ore, rigorous quality control measures were necessary to protect groundwater in the area. Nevada’s Department of Environmental Protection gave its final authorizations for the expansion on Sept. 20 following completion of the construction on Aug. 13.
“State of Nevada regulations require zero degradation to groundwater, so even trace amounts of cyanide are unacceptable,” Ferriter explained. “It’s a zero-discharge facility, meaning from the liner to the ponds and back again, it’s a continuous loop, with absolutely no discharge.”
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But how does heap leaching work, exactly?
Heap leaching became a popular method of extracting gold in the early 1900s and started becoming even more sophisticated and widespread between the 1960s and 1980s. Dozens of major mining operations throughout the world currently use the technique for extracting precious metals.
Gold-bearing ore gets crushed down to a size that will enable optimal leaching. This ore then gets stacked on an impermeable pad like Calibre just installed. Recent innovations in liner technology have helped minimize the likelihood of an environmental incident.
For the next step, a cyanide solution is sprayed or dripped over the ore pile, which dissolves the gold from the ore. As this gold-bearing solution trickles down through the pile, it gets collected in a drainage system at the base of the pad.
The gold-rich solution obtained from the base is then sent to a processing plant for further refinement.
Heap leaching has enabled mining operations to process ore with gold content as low as 0.5 grams per tonne.
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