Nighthawk Announces Latest Colomac Metallurgical Testwork

Nighthawk Gold Corp. (TSX:NHK) provided results from its ongoing preliminary metallurgical testwork on the Colomac gold project.

As quoted in the press release:

Findings reveal: a relatively uniform hardness for material tested to-date; that the rock is amenable to all standard gold recovery technologies; and using a combination of gravity and cyanide leach recovery processes, testing showed that gold recoveries range from 96.5 percent on the lower-grade material and up to 98.0 percent on the higher-grade rock.

Two initial bottle roll leach tests were carried out to assess cyanide heap leach feasibility. Minus 12,700 micron (1.27 centimetre) material registered up to 81.8 percent recoveries on lower-grade rock (1.81 grams per tonne gold head grade) and 57.50 percent on the higher-grade material (4.99 grams per tonne gold). One column leach test has been completed to date on higher-grade mineralization posting a recovery of 34.30 percent. Such noted recovery variability is not uncommon as significant fluctuations have also been documented in recent metallurgical studies on other notable northern deposits and is largely a function of the particle size that interacts with the leachate.

Highlights are as follows:

• Minimal variation in rock hardness of all test samples indicates relatively homogeneous host rock;
• Favourable recoveries were achieved for all process options, including, flotation, gravity separation, and heap leaching;
• Gold extraction by flotation ranged from 90.7 percent – 94.6 percent with maximum tested recoveries achieved at a feed size F₈₀ of 75 microns (optimum grade-recovery performance was not examined);
• Cyanidation of ground rock after gravity concentration increased gold recoveries significantly up to 98.0 percent;
• Cyanide heap leach results show considerable variability between testing methods and grade of material processed but fall within expected performance range for crushed ore (recoveries between 34.30 percent up to 81.8 percent).

Dr. Michael Byron, president and CEO, commented:

Although at the early stages of metallurgical testwork, the results to-date describe Colomac rock as exceptional in terms of grind characteristics, gold recoveries, purity, and responsiveness to all standard gold recovery technologies. We are also encouraged by the preliminary heap leach bottle roll and column test results. Although initial heap leach gold recoveries show significant variability, other northern deposits including the Fort Knox mine in Alaska, and Yukon’s Coffee gold deposit, Eagle gold project, and the Brewery Creek Mine all note variability in their recoveries. To address this, 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 we continue to evaluate the potential heap leach option for the project

Click here to read the full Nighthawk Gold Corp. (TSX:NHK) press release.