Nighthawk mulls heap leaching option at Colomac gold project
Nighthawk Gold Corp. [NHK-TSXV; MINZF-OTC] on Tuesday May 22 announced results from ongoing preliminary testwork its 100%-owned Colomac gold project in the Northwest Territories.
Nighthawk Gold is taking a fresh look at Colomac amid speculation that former operator Royal Oak Mines may have misinterpreted the geology and therefore vastly underestimated the potential around a former open pit mine that produced 528,000 ounces of gold between 1990 and 1997.
The claims and leases that contain the former Colomac open pit gold mine are part of the much larger Indin Lake property, which covers 90,000 hectares and is thought to contain 20 gold deposits.
Five of those deposits are located on the Colomac leases, which are known to host a NI 43-101 compliant inferred resource of 2.1 million ounces of gold, grading 1.64 g/t.
On Tuesday, the company said the metallurgical testwork revealed the following results:
- A relatively uniform hardness for material tested to date;
- That rock is amenable to all standard gold recovery technologies;
- Using a combination of gravity and cyanide leach recovery processes, testing showed that gold recoveries range from 96.5% on the lower grade material and up to 98% on the higher grade rock, representing a significant increase in recovery over historic production results of 88.1% (1994 to 1997).
The company said two initial bottle roll leach tests were carried out to assess cyanide heap leach feasibility. Minus 12,700 micron (1.27 cm) material registered up to 81.8% recoveries on lower-grade rock (1.81 g/t gold, head grade) and 57.50% on the higher grade material (4.99 g/t gold). One column leach test has been completed to date on higher grade mineralization posting a recovery of 34.30%.
Despite the variability, Colomac results convey a positive indication of the deposit’s heap leach potential, falling within the expected performance ranged for crushed ore, the company said.
Addressing the variability issue and metallurgical testing is planned for 2018 that will cover some of the other mineralized zones, and will include additional bottle roll and column leach testwork as the company continues to evaluate the potential heap leach option for the project.
In Tuesday’s press release, Nighthawk President and CEO Dr. Michael Byron noted that other northern deposits all showed variability in their recoveries.
They include the Fort Knox Mine in Alaska, the Yukon’s Coffee gold deposit, Eagle gold project and the Brewery Creek Mine.
On Tuesday, Nighthawk shares eased 11.11% or $0.06 to 48 cents. The 52-week range is $1.15 and 48.5 cents.