High and Rapid Recoveries Relatively Insensitive to Crush Size Continue to Support Simple Heap Leach Processing
VANCOUVER, B.C. – Liberty Gold Corp. (LGD-TSX) (“Liberty Gold” or the “Company”) is pleased to report results from Phase 2 metallurgical column testing on oxide material from drill core at its Black Pine Project in southeastern Idaho.
Gold extractions from 29 variability composites designed to test the full range of rock types and grades encountered in the drill holes were rapid, with >80% of the leachable gold extracted within 10 days, and final column leach gold extractions ranging up to 94.5%. These results are in-line with and slightly better than Phase 1 bulk sample column test results (78.9% weighted average extraction) and historical column tests from bulk samples and drill core (80.8%) (see press release June 16, 2020).
The Phase 2 metallurgical test work continues to provide support for a simple heap leach mining scenario. Large diameter core drilling in support of a Phase 3 metallurgical test program will commence on August 19, targeting the recent D-3 discovery, D-1 Southeast Extension, F zone and new M Zone target.
Metallurgical test work included fine and coarse bottle rolls and column tests using 0.5 inch (12.7 millimetre (“mm”)) and 1 inch (25.4 mm) crushed material. In total, 87 bottle rolls (29 coarse mesh and 58 fine mesh) and 29 column tests were carried out on material composited from six large diameter (PQ) drill holes in the D-1, D-2 and Rangefront target areas.
Results from the metallurgical test work demonstrate that oxide material from Black Pine responds well to column testing and should contribute to low capital and operating costs in the future. The test work undertaken on the project to date has significantly mitigated the metallurgical risk related to the known mineralization. Virtually no transitional or sulphide mineralization has been encountered to date at Black Pine in over 2000 drill holes.
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 Black Pine continue to indicate rapid leaching and relatively high gold extractions, with a remarkable insensitivity to particle size, and suggest that a combination Run of Mine and coarse crush/agglomeration heap leaching may be the preferred process options at Black Pine.”
Key Points:
•Twenty-nine column leach tests produced a weighted average* 82.9% gold extraction. With a range up to 94.5% gold extraction. See Table 1, below, or click here: https://libertygold.ca/images/news/2020/August/Gold_Extraction_Data.pdf
•Gold extraction was rapid, with >80% of the leachable gold extracted within the first 10 days of column leaching. See Figure 1, below or click here: https://libertygold.ca/images/news/2020/August/Cumulative_Leach_Curves.pdf
•Percent gold extraction is well-correlated with head grade, with the highest-grade composites returning the highest extraction numbers.
•Twenty-nine coarse bottle roll tests (target of 80% passing 10 mesh or 1.7mm particle size) produced a weighted average 78.8% gold extraction.
•Twenty-nine fine bottle roll tests (target of 80% passing 200 mesh or 75 micron particle size) produced a weighted average 81.5% gold extraction for direct leach, and 29 fine bottle roll tests produced a weighted average 84.1% for carbon in leach (“CIL”).
•Gold extraction is relatively insensitive to particle size. Most composites can be projected to coarse particle sizes approximating run of mine conditions without significant loss of gold extraction.
•Results generated by this program are consistent with historical column test results generated by Noranda in 1988 prior to mining, as well as Phase 1 metallurgical testing by Liberty Gold using large diameter columns and 300 kilogram bulk samples.
•A first-ever metallurgical test of material from the Rangefront Zone, located approximately 2.5 km southeast of the D-2 zone and other holes used for this study, returned extractions ranging up to 81.5% from four composites.
*Weighted average gold extraction is obtained using the following equation: (composite head grade (grams/tonnes) multiplied by 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 column tests is 75%.
“We are extremely pleased with the results from our bulk sample and variability column testing programs at Black Pine, which compare well with other oxide heap leach operations and development projects in the Great Basin,” said Moira Smith, Vice President of Exploration and Geoscience for Liberty Gold. “By testing the entire range of grades and rock types, we can better understand the metallurgical characteristics of the gold system across the board and design a process flow sheet that accommodates the variability that we see. Large diameter core drilling for Phase 3 metallurgical testing in other parts of the gold system will commence in a few days.”
Table 1: Column Test and Bottle Roll Results, Liberty Gold Variability Composites
see & read more on
https://libertygold.ca/news/2020-news/387-liberty-gold-reports-weighted-average-82-9-extraction-in-phase-2-metallurgical-column-testing-at-black-pine-project,-great-basin,-usa.html |
