Mr. Nav Dhaliwal reports
BONTERRA ACHIEVES UP TO 99.4% GOLD RECOVERIES FROM PRELIMINARY METALLURGICAL STUDIES, INCLUDING UP TO 76.1% FROM THE GRAVITY CIRCUIT
Bonterra Resources Inc. has received highly positive results for its preliminary metallurgical testwork, which forms part of its continuing resource development program at its 100-per-cent-controlled Gladiator gold deposit in Quebec, Canada. Results to date show total gold recoveries of up to 99.4 per cent, including 76.1 per cent from the gravity circuit.
"The outstanding metallurgical results, when compared to the overall average lower recoveries within our industry peer group, are a significant milestone for the Gladiator gold deposit. The exceptional gravity recovery rates of up to 76.1 per cent, combined with a simple flotation circuit, may reduce capital requirements related to a future potential milling operation,"commented Nav Dhaliwal, chief executive officer of Bonterra. "Potentially not requiring a cyanide leaching circuit minimizes the environmental footprint of any future mining operation and could also improve potential future process economics of the project."
Highlights and observations:
The combination of gravity and gravity cyanide tests resulting in significant gold recoveries of 99.0 per cent to 99.4 per cent;The combination of gravity and gravity tail flotation tests resulting in significant gold recoveries of 96.8 per cent to 97.3 per cent;Excellent gravity concentrate recoveries, ranging from 68.3 per cent to 76.1 per cent, well above the average of Bonterra's industry peers and confirm the presence of a significant amount of free gold in the mineralized system;Average greater than 70 per cent of the gold reported to the gravity circuit at all grinding test sizes, indicating substantial potential capital and operating savings in the grinding circuits;A cyanide leaching circuit may notbe required, noting the high recovery of the gold from the gravity and gravity tail flotation tests;Head assay results from the metallurgical testing ranged from 8.0 grams per tonne gold to 10.0 g/t Au and showed excellent grade reconciliation with initial drill hole assays.
"As expected, preliminary metallurgical test results confirmed excellent gold recoveries. On average, greater than 70 per cent of the gold reports to the gravity circuit at all grinding sizes, which potentially contributes to substantial capital reductions in the grinding circuits, potential lower reagent consumption and highlights an opportunity for significant savings in the future processing parameters at Gladiator," commented Peter A. Ball, vice-president, operations."The simple metallurgy, consisting of potentially only a crushing and grinding circuit to achieve 76.1-per-cent recovery, provides a low capex/opex process to pour gold bullion on site. Adding a flotation circuit could yield up to 97.3-per-cent recovery and deliver a very high-grade gold concentrate, making material very compatible and easily transported to a local or a centralized standard milling facility."
Metallurgical program review
ALS Metallurgy of Kamloops, B.C., was contracted to complete gravity concentration, flotation and cyanide leach testing for the gladiator gold deposit. The studies included grind optimization, gravity separation, flotation and cyanide leach testing, and were intended to provide an initial look at the characteristics of mineralization to help guide future optimization testwork and processing flow sheet specifications.
Over all, the metallurgical testing and microscopic analysis indicate that the mineralization is relatively simple with no deleterious elements, and preconcentration could potentially be achieved by a low-capital-intensive processing sequence, which will likely include crushing, grinding, gravity concentration and flotation. The process is a relatively benign one, and also offers potential environmental permitting advantages, as well as significant savings in transportation costs. These results are part of a continuing comprehensive metallurgical program designed to define the processing parameters, establish grade-recovery relationships and optimize gold recovery for a potential future Gladiator milling facility.
ALS completed testing on approximately 35 kilograms of composite sample from the main zone with an average head grade of 9.0 g/t Au from two wide-diameter holes MT-18-01 and MT-18-02. The composite sample was selected to be representative of the deposit mineralization based on mineralogy, grade and location. Head assay results from the metallurgical testing ranged from 8.0 g/t Au to 10.0 g/t Au and showed excellent grade reconciliation with initial drill hole assays.
Four kg of the sample, at three different grind sizings, were submitted for gravity separation using a Knelson concentrator. Gold recovery by the Knelson gravity separation was followed by hand panning to produce a final gravity concentrate mass that is more representative of plant operation. The pan concentrate, pan tailings, and Knelson concentrator tails were assayed for gold and determined that gold in the samples were highly amenable to gravity recovery.
RESULTS OF THE GRAVITY CONCENTRATION GOLD RECOVERY TESTS TestSize Feed grade Knelson tailsPan tailsPan concentratePan concentrate (g/t Au) (%)(%)(%) (g/t Au)1 169 mm K80 9.1920.0 11.7 68.33,6272 136 mm K80 9.8613.6 11.9 74.54,437383 mm K80 8.7013.0 10.8 76.16,461 RESULTS OF THE FLOTATION CONCENTRATION GOLD RECOVERY TESTSTest Size Feed grade Gravity recovery Rougher recovery Total recovery --(g/t Au)distribution % distribution %distribution % Au SAuS AuS4 169 mm K8010.0 73.018.823.5 72.0 96.5 90.85 136 mm K808.00 70.917.126.0 73.9 96.8 91.0683 mm K808.28 73.813.023.5 78.5 97.3 88.2RESULTS OF THE CYANIDE CONCENTRATION GOLD RECOVERY TESTSTestSize Leach feed Au recovery gravityLeach extractionAu recovery gravity tailsAu recovery total(gravity tails) (%) (%)(%)(%)7 169 mm K80 test 168.330.7 30.7 99.08 136 mm K80 test 274.524.9 24.9 99.4983 mm K80 test 376.123.1 23.1 99.2
A kinetic rougher test was included in each flotation feed sizing. This test determined that gold in the samples is highly amenable to recovery using a standard froth flotation circuit.
Gravity plus cyanidation leach tests were completed, and it was determined that gold in the samples responded excellent to conventional leaching. Three of the tests were conducted on the samples at each grind sizing, and three of the tests were conducted on the rougher flotation tailings.
Bonterra is currently completing a resource development program in 2018 at the Gladiator gold deposit, including approximately 70,000 m of drilling, metallurgical studies and a mineral resource update.
Robert Gagnon, PGeo, has approved the information contained in this release.Mr. Gagnon is a director of Bonterra and is a qualified person as defined by National Instrument 43-101.
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