News Release

Nighthawk Reports Preliminary Metallurgical Results of up to 96.5% Gold Recoveries at Colomac

Toronto, Ontario, April 19, 2017 – Nighthawk Gold Corp. (“Nighthawk“) (TSX Venture: NHK) is pleased to announce encouraging preliminary results from its ongoing metallurgical test work program on the Colomac Gold project.  Testing was completed at Bureau Veritas in Richmond, BC, and audited by Starkey & Associates Inc. in Oakville, Ontario.  Three drill core bulk samples from various portions of the Colomac gold deposit were assayed and tested for grindability using the SAGDesign methodology.  A master composite was then amalgamated from the bulk samples and used for additional metallurgical testing. Initial results indicate that gold recoveries of up to 96.5% may be achieved and the rock is amenable to all standard gold recovery technologies. This represents a significant increase in recovery over the historic production results of 88.1% (1994 to 1997). Additional testwork is expected to yield further optimization and confirmation of these results.

Highlights include:

  • Variation in rock hardness of the three bulk samples was minimal indicating that the material is relatively homogeneous;
  • The master composite sample, having a head grade of 1.81 grams per tonne gold measured by fire assay, generated favourable recoveries for all process options, including heap leaching, flotation, and gravity separation;
  • Gold extraction by flotation ranged from 94.1% - 95.5% with maximum recoveries achieved at a feed size F80of 151 microns;
  • Cyanide heap leaching of minus 12,700 micron material reported up to 81.8% gold recoveries, perhaps an option for lower grade material which would otherwise be considered waste;
  • Cyanidation of ground rock increased gold recovery significantly up to 96.5%.

“Results from this initial metallurgical testing have significantly exceeded our expectations in comparison to Colomac’s known historical recoveries”, commented Nighthawk President & CEO, Dr. Michael Byron. “In particular, Colomac material shows excellent grind characteristics, exceptional gold recoveries and responsiveness to all standard gold recovery technologies, comparing favourably to similar projects in North America.  It’s also important to note that the rock is exceptionally clean as no deleterious materials were detected that could otherwise adversely affect processing, or impact the environment. We are very pleased with the initial results, and expect the final testwork to confirm these findings”.

The three drill core bulk samples, totalling 119.5 kilograms of split drill core, were of similar mineralogical characteristics. In addition to hardness testing (Table 1.0), they were also used to address the spatial and grade variations of the quartz diorite host rock (Table 2.0).  Each sample was assayed and tested to obtain individual grinding parameters.  Grinding tests indicate that all samples exhibit a consistent high hardness, and minor variability, presenting no milling issues.  The average SAG Grindability for the three samples was measured as 13.31 kWh/tonne (Grinding from F80 6” to P80 1.7 mm) and 14.25 kWh/tonne for the Bond Ball Mill Work Index on SAG ground rock.  A master composite sample was subsequently blended from the South Zone and Deep bulk samples in an effort keep the head grade as high as possible for the metallurgical testing. The North Zone sample was omitted from the master composite due to its lower grade.


Table 1. SAGDesign Test Summary

SG Solids WSDT
South Zone 2.76 12.32 14.28
North Zone 2.73 13.52 14.38
Deep 2.70 14.07 14.10
Average 2.73 13.31 14.25


Table 2. Head Assays of Colomac Samples

Sample Information

Fire Assay
(g Au/t)

Screen Metallics Assay (g Au/t)
South Zone 1.16 1.32
North Zone 0.35 0.90
Deep 0.65 1.69

The master composite, reporting a head grade of 1.81 grams per tonne gold, was tested for gold recovery amenability, specifically by cyanide leaching, flotation, and gravity separation.  Favourable recoveries were achieved for all process options.  Gold recoveries by flotation ranged from 94.1% - 95.5% with maximum recoveries achieved at a feed size F80 of 151 microns. Cyanide heap leaching of minus 12,700 micron material reported up to 81.8% recoveries; however, given the deposit’s northern location, this may only be an option for seasonal processing of lower grade material which would otherwise be considered waste. Highest recoveries were achieved by cyanidation of ground rock with an impressive 96.5% recovery. A summary of that metallurgical test work is shown in Table 3.  


Table 3. Master Composite Test Results

Description Particle Size P80 (microns) Au Recovery
Flotation Fine 75 94.9
Medium 105 94.1
Coarse 151 95.5
Gravity (Centrifuge) Fine 75 33.3
Medium 105 45.0
Coarse 150 25.9
Leaching Heap -12,700 81.8
Whole Ore 148 96.4
Gravity + Leach 105 96.5


Future Testing

Although the findings of this testwork program indicate the Colomac deposit is amenable to all standard recovery technologies, the flowsheet developed on the master composite is viewed as preliminary in nature.  Future testwork is planned on samples which are more representative of the various gold zones within the deposit; in particular, the high-grade zones such as Zone 1.5, which is to be sampled during the current drill program.  The main purpose is to confirm that metallurgical responses observed in this testwork apply over a broader range of head grades.  However, given these excellent initial recoveries reported for the lower grade material it may be expected that similar, or possibly better recoveries may be achieved with the higher grade material.

Quality Control

The technical information disclosed herein was prepared under the supervision of Dr. Alice Shi of Bureau Veritas and qualified person, Mr. John Starkey of Starkey & Associates Inc.  Mr. Starkey has supervised the metallurgical work reported on and has reviewed and approved the technical disclosure contained in this news release with respect to such work.

Dr. Michael J. Byron, Ph.D., P.Geo., President & Chief Executive Officer of Nighthawk, who is the “Qualified Person” as defined by NI 43-101 for this project, observed the collection of the samples for metallurgical testing, reviewed the progress on the metallurgical testing on multiple occasions and has also reviewed and approved of the technical disclosure contained in this news release. 

About Nighthawk

Nighthawk is a Canadian-based exploration company focused on acquiring and developing gold mineral properties in the Northwest Territories. Including the mineral claims and leases of the Colomac Gold Project, Nighthawk’s Indin Lake Gold Property comprises a total land package of 222,203 acres in the Indin Lake Greenstone Belt, located approximately 200 kilometres north of Yellowknife, Northwest Territories and includes an Inferred Mineral Resource estimate, prepared in accordance with National Instrument 43-101 (“NI 43-101”), of 39.815 million tonnes with an average grade of 1.64 g/t gold for 2.101 million ounces gold using a cut-off grade of 0.6 g/t gold. Nighthawk also holds a 100% interest in the property known as the Superior Project, which covers 39,015 acres approximately 85 kilometres north of Sault Ste. Marie, Ontario.


Nighthawk Gold Corp.

Dr. Michael J. Byron
President and CEO
Tel: (705) 560-2382
Suzette N. Ramcharan
VP, Corporate Development
Tel: (647) 284-5315

Forward-Looking Statements

Certain information set forth in this news release may contain forward-looking statements that involve substantial known and unknown risks and uncertainties, including, but not limited to, the timing of future drilling, the expansion of the mineralization, and the remediation of historic reclamation sites. These forward-looking statements are subject to numerous risks and uncertainties, certain of which are beyond the control of Nighthawk, including, but not limited to, the impact of general economic conditions, industry conditions, volatility of commodity prices, risks associated with the uncertainty of exploration results and estimates, currency fluctuations, dependency upon regulatory approvals, the uncertainty of obtaining additional financing and exploration risk. Readers are cautioned that the assumptions used in the preparation of such information, although considered reasonable at the time of preparation, may prove to be imprecise and, as such, undue reliance should not be placed on forward-looking statements. This press release is not, and is not to be construed in any way as, an offer to buy or sell securities in the United States.

Neither TSX Venture Exchange nor its Regulation Services Provider (as that term is defined in the policies of the TSX Venture Exchange) accepts responsibility for the adequacy or accuracy of this release.


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