Fitzroy Minerals Reports Copper Recoveries of up to 82.6% from Mini-Column Testing, with Preliminary Larger-Scale Results Trending Higher, at the Buen Retiro Copper Project, Chile
Fitzroy Minerals Inc. (TSXV: FTZ, OTCQX: FTZFF, FSE: C3Y) (“Fitzroy” or the “Company”) is pleased to announce results from the initial phase of metallurgical test work completed by SGS Laboratories (“SGS”) at the Buen Retiro Copper Project, Copiapó, Chile (“Buen Retiro” or the “Project”). The test program is evaluating the response of the Project’s three principal geometallurgical units (“UGM” or “Units”) to heap-leach processing, to support the Company’s planned Heap Leach Development Plan. The distinct units, based on mineralogy and grade are high-grade oxide, low-grade oxide, and Mixed. Mini-column testing, the first stage of column-based testing, is now complete, while larger-scale 1-metre column tests are ongoing and are already trending above the mini-column results.
Highlights:
- Mini-column testing confirms a favourable response to heap leaching across all three Units, with total copper (“CuT”) recovery of 71.8% (high-grade oxide), 59.9% (low-grade oxide) and 82.6% (mixed) after 21 days, with low-to-moderate net acid consumption (3.4 to 11.2 kg/kg) and excellent test reproducibility.
- Preliminary results from 1-metre column tests are trending above the mini-column figures, still trending upwards, and pointing to further improvement in copper recovery as leach time and scale increase. Projections of the trend lines indicate column recoveries after 70 days of approximately 95% (mixed), 85% (high-grade oxide) and 74% (low-grade oxide). To determine the expected industrial Cu recovery, those results should typically be multiplied by a scaling factor between 0.8 and 0.9.
- Favourable rock hardness (<8 kWh/t, “soft”) and medium-to-moderate abrasiveness.
- The addition of chloride during agglomeration and leaching was identified as an opportunity to optimize copper recovery and acid consumption.
Merlin Marr-Johnson, President and CEO of Fitzroy, commented: “These results exceed what we were hoping for from our first phase of metallurgical testing at Buen Retiro. Final copper recoveries of up to 82.6%, achieved with low acid consumption and excellent reproducibility across three separate Units in just 21 days, give us real confidence in the heap-leach case for the Project. Even more encouraging is that the more representative, one-metre columns are trending higher, pointing towards a final recovery of 95% after 75 days of leaching, for the Mixed material. Combined with soft, easily-crushed, moderately abrasive rock, this test work materially de-risks our path toward heap-leach production at Buen Retiro. The work is being done on a large number of samples and is statistically robust. We look forward to closing out the one-metre column balances this month, starting three-metre column testing in November, and reporting final metallurgical results in due course.”
Test Program and Sample Basis
Buen Retiro’s mineralization is classified into three principal geometallurgical units based on grade and mineralogy: high-grade oxide (CuT ≥ 0.5%), low-grade oxide (CuT between 0.2% and 0.5%), and mixed (characterized by the presence of tenorite, cuprite, native copper, chalcocite and green oxides).
Three composite samples (1,349 kg, 1,566 kg and 426 kg, representing high-grade oxide, low-grade oxide, and mixed, respectively) were shipped to SGS’s laboratory in Quilicura, Santiago, for metallurgical testing. In total 3,341 kg has been submitted which will be subject to 208 separate tests. The test program is designed upon a staged approach:
- Iso-pH: 45 tests of 1 kg
- Sulphation at laboratory scale: 66 tests of 2 kg
- Mini-columns (40 cm x 4” diam.): 55 tests of 5 kg
- 1-metre columns (100 cm x 6” diam.): 30 tests of 30 kg
- 3-metre columns (300 cm x 6” diam.): 12 tests of 90 kg
At each successive stage the operating variables carried forward are narrowed in scope. In total, ten mini-column tests were completed (six across the high- and low-grade oxide Units, and four for the mixed Unit), together with hardness (Bond) and abrasiveness testing, and TIMA and XRD mineralogical analysis.
Mini-Column Results (Closed Metallurgical Balance)
The mini-column campaign has been completed, with a closed metallurgical balance. The head grades of the three composites tested were as follows:
- High-grade oxide: 0.95% CuT, with sequential copper analysis of 0.68% acid-soluble Cu, 0.04% cyanide-soluble Cu, and 0.23% residual Cu.
- Low-grade oxide: 0.35% CuT, with sequential copper analysis of 0.18% acid-soluble Cu, 0.05% cyanide-soluble Cu, and 0.12 % residual Cu.
- Mixed material: 1.24% CuT, with sequential copper analysis of 0.67% acid-soluble Cu, 0.30% cyanide-soluble Cu, and 0.27% residual Cu.
Carbonate contents are relatively low, at 0.13% for the high-grade oxide, <0.05% for the low-grade oxide, and 0.44% for the mixed material.
The test feed granulometry was 90% < ¼ in. At 21 days of leaching, under the best treatment conditions tested for each Unit type, total copper recoveries of 71.8%, 59.9% and 82.6% were achieved, respectively, at specific acid consumptions of 4.9, 11.2 and 3.4 kg H+/kg Cu (Table 1). Duplicate mini-column tests returned copper extractions within 1 percentage points of one another (Table 2), confirming good reproducibility. There is no duplicate results yet for the mixed ore tests.
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