Liberty Gold Reports Weighted Average 84.2% Extraction in Phase 2 Column Testing at Goldstrike Project, Great Basin, USA
VANCOUVER, British Columbia, May 28, 2019 (GLOBE NEWSWIRE) -- Liberty Gold Corp. (LGD-TSX) (“Liberty Gold” or the “Company”) is pleased to report results from Phase 2 metallurgical testing on oxide material from its Goldstrike Project, in southwestern Utah, providing additional support for a simple heap leach mining scenario. Gold extractions from 29 column tests were rapid, and >80% of the leachable gold was extracted within 10 days, with final column leach gold extractions ranging up to 95%.
Metallurgical testwork included fine and coarse bottle rolls and 12.5 millimeters (“mm”) (0.5 inch) and 25 mm (1 inch) column tests. In total, 58 bottle rolls (twenty-nine 200 mesh and twenty-nine 10 mesh) and 29 column tests were carried out on 29 composites from the Dip Slope Zone immediately north of the Main Zone (subject to Phase 1 testing) and the Western Zone. Metallurgical testing now extends to all areas within the footprint of the Resource Estimate and Preliminary Economic Assessment (“PEA”).
Results and conclusions are consistent with those generated from Phase 1 metallurgical testing (see press release dated April 3, 2017), which were used to underpin recovery assumptions and run-of-mine (“ROM”) flow sheet for the PEA (see press release dated July 10, 2018). The Phase 2 metallurgical testing brings the total number of oxide column tests for the property to 49. A slight drop in overall extraction for Phase 2 results (84.2%) relative to Phase 1 results (85.9%) can be attributed to an average grade of 0.669 grams per tonne gold (“g/t Au”) for the 2019 composites, compared to 1.196 g/t Au for the 2017 composites. This difference is the result of a deliberate attempt to match the composite grades to the average grades of the geographical areas tested, in order to be able to more closely predict expected mine recoveries in these areas.
- 29 Column leach tests produced a weighted average 84.2% gold extraction (See below for a table of results or link: https://libertygold.ca/images/news/2019/may/Gold_Extraction_Data.pdf)
- Gold extraction was rapid, with >80% of the leachable gold extracted within the first 10 days of column leaching. Columns were deactivated after 50 days instead of the usual 90 day leach cycle because leaching was essentially complete. (See below for a graph of extraction curves or link: https://libertygold.ca/images/news/2019/may/Cumulative_Leach_Curves.pdf).
- Twenty-nine coarse bottle roll tests (target 80% passing 10 mesh or 1.7mm particle size) produced a weighted average 84.4% gold extraction.
- Twenty-nine fine bottle roll tests (target 80% passing 200 mesh or 75 micron particle size) produced a weighted average 89.7% gold extraction.
- Gold extraction is relatively insensitive to particle size, except for five composites from the Beavertail area. All other composites can be projected to coarse particle sizes without significant loss of gold extraction.
- Weighted average modeled extraction for the 29 column tests at a 200mm particle size (8 inches, meant to simulate ROM conditions) is 81.3%.
*Weighted average gold extraction is obtained using the following equation: (composite head grade (g/t) x extraction (%) for all head grades)/sum of all head grades. Using arithmetic averages tends to over-represent low grade composites and under-represent high grade composites. The arithmetic average of the 29 coarse bottle rolls is 81.0%. The arithmetic average of the 29 column tests is 81.5%.
“We are extremely pleased with the Phase 2 metallurgical results,” says Cal Everett, Liberty Gold President & CEO. “The results are exceptional and continue to support our belief that a high percentage of the gold can be rapidly recovered in a simple, low cost, heap leach operation. Consistent results have now been confirmed along the initial 7 kilometers of strike of the Goldstrike oxide gold system.”
The work was supervised by independent consulting metallurgist Gary Simmons, formerly the Director of Metallurgy and Technology for Newmont Mining Corp. Mr. Simmons has managed or supervised a significant number of metallurgical testing programs on similar deposits throughout the Great Basin. According to Mr. Simmons, “Data from metallurgical testing to date at Goldstrike point to rapid leaching and relatively high gold recoveries and suggest that a combination ROM and coarse crush/agglomeration heap leaching may be the preferred process option at Goldstrike.”
Samples for this study were collected from 13 large diameter (PQ) diamond drill holes from the Western Zone of the Goldstrike Deposit as well as two areas near the Main Zone, intended to expand the scope of testing initiated with Phase 1, which focused entirely on the Main Zone.
For a map showing locations of drill holes used for metallurgical testing, please click here:
13 large diameter diamond drill holes were drilled in 2018 to sample a range of locations and material types in the Main and Western Zones at Goldstrike. From these, 29 composites were created for metallurgical testing, with gold grades ranging from 0.214 to 2.048 g/t Au. All composites were dominantly oxide, with cyanide soluble gold content of >80%.
Composites were sent to Kappes, Cassiday and Associates in Reno, Nevada for metallurgical testing, comprising bottle rolls, column testing and metallurgical characterization including; gold and silver assays, cyanide solubility, sulphur and carbon speciation, preg-robb analysis, ICP geochemical assays and whole rock analysis.
Column composites were leached in either 100 mm (4 inch) or 150 mm (6 inch) diameter columns at low strength, 0.50 grams per litre of sodium cyanide (“NaCN”) solution. Five of the columns sampleswere agglomerated with 2.0 kg/t of cement due to elevated clay content.
Samples for bottle roll testing were crushed/pulverized to 80% passing 200 mesh (75 microns) and 80% passing 10 mesh (1.7 mm) particle size. The samples were rolled/agitated in bottles in a 1.0 g/l dilute cyanide solution for 72 hours (for 200 mesh) or 144 hours (for 10 mesh).
Organic carbon values are low. Results to date suggest that organic carbon will not be an issue in recovery.
Goldstrike is located in the eastern Great Basin, immediately adjacent to the Utah/Nevada border, and is a Carlin-style gold system, similar in many ways to the prolific deposits located along Nevada’s Carlin trend. Like Kinsley Mountain and Newmont’s Long Canyon deposit, Goldstrike represents part of a growing number of Carlin-style gold systems located off the main Carlin and Cortez trends in underexplored parts of the Great Basin. The historic Goldstrike Mine operated from 1988 to 1994, with 209,000 ounces of gold produced from 12 shallow pits, at an average grade of 1.2 g/t Au.
A virtual site tour and 3D model of Goldstrike is available on the homepage of the Company’s website: www.libertygold.ca.
Moira Smith, Ph.D., P.Geo., Vice-President Exploration and Geoscience, Liberty Gold, is the Company's designated Qualified Person for this news release within the meaning of National Instrument 43-101 Standards of Disclosure for Mineral Projects ("NI 43-101") and has reviewed and validated that the information contained in the release is accurate. Drill composites were calculated using a cut-off of 0.20 g/t. Drill intersections are reported as drilled thicknesses. True widths of the mineralized intervals vary between 30 and 100% of the reported lengths due to varying drill hole orientations, but are typically in the range of 60 to 80% of true width. Drill samples were assayed by ALS Limited in Reno, Nevada for gold by Fire Assay of a 30 gram (1 assay ton) charge with an AA finish, or if over 5.0 g/t were re-assayed and completed with a gravimetric finish. For these samples, the gravimetric data were utilized in calculating gold intersections. For any samples assaying over 0.200 ppm an additional cyanide leach analysis is done where the sample is treated with a 0.25% NaCN solution and rolled for an hour. An aliquot of the final leach solution is then centrifuged and analyzed by Atomic Absorption Spectroscopy. QA/QC for all drill samples consists of the insertion and continual monitoring of numerous standards and blanks into the sample stream, and the collection of duplicate samples at random intervals within each batch. Selected holes are also analyzed for a 51 multi-element geochemical suite by ICP-MS. ALS Geochemistry-Reno is ISO 17025:2005 Accredited, with the Elko prep lab listed on the scope of accreditation.
ABOUT LIBERTY GOLD
Liberty Gold is focused on exploring the Great Basin of the United States, home to large-scale gold projects that are ideal for open-pit mining. This region is one of the most prolific gold-producing regions in the world and stretches across Nevada and into Idaho and Utah. We know the Great Basin and are driven to discover and advance big gold deposits that can be mined profitably in open-pit scenarios. Our flagship projects are Goldstrike, Black Pine and Kinsley Mountain, all of which are past producing open-pit mines, where previous operators only scratched the surface.
For more information, visit www.libertygold.ca or contact:
Susie Bell, Manager, Investor Relations
Phone: 604-632-4677 or Toll Free 1-877-632-4677
All statements in this press release, other than statements of historical fact, are "forward-looking information" with respect to Liberty Gold within the meaning of applicable securities laws, including statements that address potential quantity and/or grade of minerals, potential size and expansion of a mineralized zone, proposed timing of exploration and development plans, expected capital costs at Goldstrike, expected gold and silver recoveries from the Goldstrike mineralized material, potential additions to the resource through additional drill testing, potential upgrade of inferred mineral resources to measured and indicated mineral resources, the potential for silver resources at Goldstrike and intentions to pursue a silver resource study and beliefs regarding gold resources being contained within a larger property area. Forward-looking information is often, but not always, identified by the use of words such as "seek", "anticipate", "plan", "continue", "planned", "expect", "project", "predict", "potential", "targeting", "intends", "believe", "potential", and similar expressions, or describes a "goal", or variation of such words and phrases or state that certain actions, events or results "may", "should", "could", "would", "might" or "will" be taken, occur or be achieved. Forward-looking information is not a guarantee of future performance and is based upon a number of estimates and assumptions of management at the date the statements are made including, among others, assumptions about future prices of gold, and other metal prices, currency exchange rates and interest rates, favourable operating conditions, political stability, obtaining governmental approvals and financing on time, obtaining renewals for existing licenses and permits and obtaining required licenses and permits, labour stability, stability in market conditions, availability of equipment, accuracy of any mineral resources, the availability of drill rigs, the accuracy of a preliminary economic assessment, successful resolution of disputes and anticipated costs and expenditures. Many assumptions are based on factors and events that are not within the control of Liberty Gold and there is no assurance they will prove to be correct.
Such forward-looking information, involves known and unknown risks, which may cause the actual results to be materially different from any future results expressed or implied by such forward-looking information, including, risks related to the interpretation of results and/or the reliance on technical information provided by third parties as related to the Company’s mineral property interests; changes in project parameters as plans continue to be refined; current economic conditions; future prices of commodities; possible variations in grade or recovery rates; the costs and timing of the development of new deposits; failure of equipment or processes to operate as anticipated; the failure of contracted parties to perform; the timing and success of exploration activities generally; delays in permitting; possible claims against the Company; labour disputes and other risks of the mining industry; delays in obtaining governmental approvals, financing or in the completion of exploration as well as those factors discussed in the Annual Information Form of the Company dated March 27, 2019 in the section entitled "Risk Factors", under Liberty Gold’s SEDAR profile at www.sedar.com.
The mineral resource estimates referenced in this press release use the terms "Indicated Mineral Resources" and "Inferred Mineral Resources." While these terms are defined in and required by Canadian regulations (under NI 43-101), these terms are not recognized by the U.S. Securities and Exchange Commission ("SEC"). "Inferred Mineral Resources" have a great amount of uncertainty as to their existence, and great uncertainty as to their economic and legal feasibility. The SEC normally only permits issuers to report mineralization that does not constitute SEC Industry Guide 7 compliant "reserves" as in-place tonnage and grade without reference to unit measures. U.S. investors are cautioned not to assume that any part or all of mineral deposits in these categories will ever be converted into reserves. Liberty Gold is not an SEC registered company.
Although Liberty Gold has attempted to identify important factors that could cause actual actions, events or results to differ materially from those described in forward-looking information, there may be other factors that cause actions, events or results not to be as anticipated, estimated or intended. There can be no assurance that such information will prove to be accurate as actual results and future events could differ materially from those anticipated in such statements. Liberty Gold disclaims any intention or obligation to update or revise any forward-looking information, whether as a result of new information, future events or otherwise unless required by law.