VANCOUVER, British Columbia, April 19, 2018 (GLOBE NEWSWIRE) -- Rockhaven Resources Ltd. (TSX-V:RK) (“Rockhaven”) is pleased to announce positive results from ongoing metallurgical test work on several of the mineralized zones at its 100%-owned and road accessible Klaza property, located in the Dawson Range Gold Belt of southern Yukon. These zones will be the focus of an updated Mineral Resource estimate that will include approximately 20,000 m of additional expansion and in-fill diamond drilling that were completed in 2016 and 2017.
Highlights from this press release include:
- Gold recoveries of 82% were obtained by flotation and cyanide leaching in the Eastern BRX Zone, using equipment already envisioned in the March 2016 PEA. The more than 300,000 ounces of gold estimated in this zone were not included in the PEA due to metallurgical uncertainties. Considerable economic and exploration upside exists across this zone and within this portion of the project area;
- The Eastern BRX, Western BRX and Central Klaza zones responded very well to pre-concentration test work. Using Dense Media Separation, the average gold grades more than doubled, with gold recoveries ranging from 87.0 to 98.2%; and,
- The revised Mineral Resource estimate is progressing well and will be complete by late May or early June.
“We are extremely excited about the opportunities provided by the results of this test program, which should greatly benefit overall Klaza project economics,” stated Matt Turner, CEO of Rockhaven Resources. “The pre-concentration results and encouraging recoveries from the Eastern BRX Zone are potential game-changers for the project, allowing lower cut-off grades to be considered and the inclusion of the Eastern BRX Zone in future economic studies. The Klaza and BRX zones are fully open to the east and, with the positive metallurgical results, will be a major focus of future exploration programs.”
The Klaza project hosts a large hydrothermal system that is concentrated within a 4 km long by 3 km wide structural corridor, which has only been tested to a maximum depth of 450 m. Eleven known mineralized zones have been identified within this corridor and all are open for expansion along strike and to depth.
The eastern portion of the project area comprises multiple, sub-parallel veins, that include the Eastern Klaza, Eastern BRX, Pika, Stroshein, and part of the AEX zones, all of which are open to the east, towards the mostly untested Kelly Porphyry. Due to the limited drilling in this area of the project, only the Eastern BRX and the Pika zones were included in Rockhaven’s December 2015 Mineral Resource Estimate.
The Eastern BRX Zone currently hosts an Inferred Mineral Resource estimate of 2,406,000 tonnes containing 317,000 oz gold and 4,127,000 oz silver at an average grade of 4.10 g/t gold and 53 g/t silver (See March 1, 2016 Technical Report on the Rockhaven website (www.rockhavenresources.com)). Previous flotation test work in the Eastern BRX Zone performed poorly, and did not produce saleable concentrates. Because of this, Mineral Resources in the Eastern BRX Zone were not included in the March 2016 preliminary economic assessment (PEA).
Metallurgical Test Program
The metallurgical test program is evaluating opportunities to optimize and simplify the flowsheet utilized in the March 2016 PEA through the addition of pre-concentration prior to milling; and investigating alternative low-cost processing options for the Eastern BRX Zone.
The current test program on run-of-mine material began with direct cyanide leaching, with subsequent work testing flotation and leaching. Good performance was observed in both scenarios, with 81% and 82% of the gold being recovered to doré by direct leaching, and leaching and flotation, respectively. The following table summarizes performance of the combined flotation and leaching flowsheet. Two stages of flotation were conducted, with a lead rougher, followed by cleaning, and a sulphide rougher.
| Product | Mass | Grade | Distrib. | CN Rec. | Overall Rec. |
| % | Au (g/t) | Au (%) | Au (%) | Au (%) | |
| Pb Cleaner Concentrate | 1.39 | 114.1 | 66.6 | 98.6 | 65.7 |
| Pb Cleaner Tails | 3.96 | 1.66 | 2.76 | 71.3 | 2.0 |
| Sulphide Rougher Concentrate | 16.17 | 3.90 | 27.3 | 51.4 | 14.0 |
| Final Tails | 78.49 | 0.09 | 3.38 | 0.0 | 0.00 |
| Total | 81.7 | ||||
Pre-concentration test work was conducted on half-core material from the Western Klaza, Central Klaza, Western BRX and Eastern BRX zones. Four composites were blended, representing each zone, and were crushed to 3/8”. Dense Media Separation (DMS) was used to evaluate pre-concentration response, at a separation Specific Gravity of 3.05. The following table shows a summary of the DMS results, with the concentrate representing the sink fraction and fines (< 1.18 mm) combined.
| Comp | Head Grade | Mass | Pre-Concentrate Grade | Recovery (%) | |||||||||
| Au (g/t) | Pb (%) | Zn (%) | S (%) | (%) | Au (g/t) | Pb (%) | Zn (%) | S (%) | Au | Pb | Zn | S | |
| EBRX | 1.88 | 0.10 | 0.27 | 6.79 | 32.5 | 5.01 | 0.27 | 0.74 | 16.09 | 87.0 | 88.8 | 89.5 | 77.5 |
| WBRX | 7.25 | 0.76 | 0.91 | 8.48 | 45.3 | 15.73 | 1.59 | 1.86 | 17.22 | 98.2 | 71.8 | 76.9 | 67.8 |
| WKZA | 1.45 | 0.27 | 0.24 | 4.07 | 24.5 | 3.80 | 0.84 | 0.79 | 2.31 | 64.7 | 66.8 | 81.2 | 93.2 |
| CKZA | 3.59 | 0.34 | 0.67 | 4.14 | 34.5 | 9.41 | 0.86 | 1.66 | 9.29 | 90.9 | 68.3 | 67.6 | 61.7 |
Significant upgrading by DMS was achieved, with good recoveries in all zones aside from Western Klaza, where the vein contains more sulphosalts and lesser amounts of sulphide minerals. Work is underway to perform bulk DMS followed by locked cycle flotation testing to evaluate performance of the overall flowsheet.
Exploration Potential
It is highly encouraging that all parts of the known Klaza deposit now respond well to metallurgical test work. It is particularly encouraging that many areas respond to simple, low-cost methods that could enable higher production rates. Within the known Klaza hydrothermal system, only the near surface areas of the Central Klaza, Western BRX and Western Klaza zones have been thoroughly explored to date.
The results of the metallurgical test work in this news release highlight multiple priority targets for future exploration. Three of the most important targets, given their proximity to the known deposits, are: 1) a number of new discoveries to the north of the Klaza Zone made in 2017; 2) the eastern projection of the Eastern BRX Zone; and 3) the Eastern Klaza Zone, which is mineralogical similar to the Eastern BRX Zone, but has only been tested by widely spaced diamond drill holes.
Updated Mineral Resource Estimate
An updated Mineral Resource estimate for the Klaza property is being prepared by AMC consultants and is anticipated to be complete in late-May to early-June. In preparation for the estimate, the Klaza and BRX zones were remodeled to incorporate approximately 20,000 m of additional diamond drilling completed in 2016 and 2017. The new estimate will utilize revised cut-off grades that reflect results from the 2018 metallurgical test program and include lower grade mineralization in the hanging walls and footwalls of the main veins, which was not modelled in the previous resource estimate.
Qualified Persons
Results for the metallurgical test program were provided and approved by Chris Martin, C.Eng., of Blue Coast Metallurgy Ltd. a qualified person for the purpose of National Instrument 43-101. All other technical information in this news release has been approved by Matthew R. Dumala, P.Eng., a geological engineer with Archer, Cathro & Associates (1981) Limited and also a qualified person for the purpose of National Instrument 43-101.
About Rockhaven
Rockhaven Resources Ltd. is a mineral exploration company focused on growth through the advancement of its Klaza project. For additional information concerning Rockhaven or its Klaza project please visit Rockhaven’s website at www.rockhavenresources.com.
Matthew Turner
President, CEO and Director
Rockhaven Resources Ltd.
T:604-687-2522
mturner@rockhavenresources.com
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This news release may contain forward looking statements based on assumptions and judgments of management regarding future events or results that may prove to be inaccurate as a result of exploration and other risk factors beyond its control, and actual results may differ materially from the expected results.