Bonterra Achieves up to 99.4% Gold Recoveries from Preliminary Metallurgical Studies, Including up to 76.1% from the Gravity Circuit
Vancouver, BC – April 17, 2018: Bonterra Resources Inc. (TSX-V: BTR, OTCQX: BONXF, FSE: 9BR1) (the “Company” or “Bonterra”) is pleased to announce that it has received highly positive results for its preliminary metallurgical testwork, which forms part of its ongoing Resource Development Program at its 100% controlled Gladiator Gold Deposit in Quebec, Canada. Results to date show total gold recoveries of up to 99.4%, including 76.1% 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%, combined with a simple flotation circuit, may reduce capital requirements related to a future potential milling operation,” commented Nav Dhaliwal, CEO 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 resulted in significant gold recoveries of 99.0% to 99.4%.
- The combination of gravity and gravity-tail flotation tests resulted in significant gold recoveries of 96.8% to 97.3%.
- Excellent gravity concentrate recoveries, ranging from 68.3% to 76.1%, are 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 >70% 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 not be 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 g/t Au 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% 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, VP Operations. “The simple metallurgy, consisting of potentially only a crushing and grinding circuit to achieve 76.1% recovery, provides a low CapEx/OpEx process to pour gold bullion on site. Adding a flotation circuit could yield up to 97.3% 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 (“ALS”) of Kamloops, British Columbia, 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 test work and processing flow sheet specifications.
Overall, the metallurgical testing and microscopic analysis indicate that the mineralization is relatively simple with no deleterious elements, and pre-concentration 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 an ongoing 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 kg 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 are summarized below:
|1||169 mm K80||9.19||20.0||11.7||68.3||3,627|
|2||136 mm K80||9.86||13.6||11.9||74.5||4,437|
|3||83 mm K80||8.70||13.0||10.8||76.1||6,461|
Results of the Flotation concentration gold recovery tests are summarized below:
|4||169 mm K80||10.0||73.0||18.8||23.5||72.0||96.5||90.8|
|5||136 mm K80||8.00||70.9||17.1||26.0||73.9||96.8||91.0|
|6||83 mm K80||8.28||73.8||13.0||23.5||78.5||97.3||88.2|
Results of the Cyanide concentration gold recovery tests are summarized below:
|Test||Size||Leach Feed (Gravity Tails)||Au Recovery
|Au Recovery Gravity Tails
|7||169 mm K80||Test 1||68.3||30.7||30.7||99.0|
|8||136 mm K80||Test 2||74.5||24.9||24.9||99.4|
|9||83 mm K80||Test 3||76.1||23.1||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.
Bonterra Resources Quick Facts:
- Well financed with approximately $60 million raised in past 14 months.
- Strong Shareholder Base including: Eric Sprott, Van Eck, Kirkland Lake Gold
- Gladiator Gold Deposit:
- Deposit extension and resource expansion underway with 60,000 m completed in 2017 and 70,000 m planned for 2018.
- Advancing to the completion of an updated NI 43-101 Mineral Resource Estimate in the second half of 2018.
- Drilled dimensions of the Gladiator Gold Deposit are currently outlined to a depth of 1,000 m below surface, and a strike length of 1,200 m.
- Gladiator remains open in all directions, where at least six distinct sub-parallel zones or mineralized horizons have been identified.
- Drilling is currently focused on the continued expansion of Gladiator Gold Deposit and exploration targets within the 10,541-hectare Urban-Barry property.
- Larder Lake Gold Property:
- 100% controlled 2,221-hectare in the Cadillac-Larder Break camp in Ontario (refer to March 17, 2016 news release highlighting historical gold resource).
- Excellent access to three high grade gold deposits between Kirkland Lake and Virginiatown.
Robert Gagnon, P.Geo., has approved the information contained in this release. Mr. Gagnon is a director of Bonterra and is a Qualified Person as defined by NI 43-101.
ON BEHALF OF THE BOARD OF DIRECTORS,
Nav Dhaliwal, President & CEO
Bonterra Resources Inc.
For further information on Bonterra, contact Investor Relations
Telephone: 1 844 233 2034
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