Nighthawk provides update on latest Colomac metallurgical testwork

TORONTO, May 22, 2018

TORONTO, May 22, 2018 /PRNewswire/ - Nighthawk Gold Corp. ("Nighthawk" or the "Company") (TSX: NHK; OTCQX: MIMZF) is pleased to provide a summary of results from its ongoing preliminary metallurgical testwork on the Colomac Gold Project ("Colomac"). 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% on the lower-grade material and up to 98.0% on the higher-grade rock (see press releases April 19, 2017 and February 21, 2018), representing a significant increase in recovery over historic production results of 88.1% (1994 to 1997).

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% recoveries on lower-grade rock (1.81 grams per tonne gold "gpt Au",head grade) and 57.50% on the higher-grade material (4.99 gpt Au). One column leach test has been completed to date on higher-grade mineralization posting a recovery of 34.30%. 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.

Higher-Grade Testwork Highlights:

• 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% - 94.6% 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%;
• 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% up to 81.8%).

Despite the variability, Colomac results convey a positive indication of the deposit's heap leach potential, falling within the expected performance range for crushed ore. Additional metallurgical work is required to arrive at a statistically relevant population of results for all deposit types, mineralized zones and corresponding grade variations. As in the previous sampling programs, testwork will be carried out on Colomac drill core from recent drilling.

Dr. Michael Byron, President & 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."

Metallurgical Testwork