The Gualcamayo process facility is designed to treat 25,000 tpd of ore through crushing, heap leaching, and carbon-based gold recovery.
Report context
The Gualcamayo property technical report, dated September 15, 2021, describes a gold processing operation using primary, secondary, and tertiary crushing followed by heap leaching, an ADR (adsorption, desorption, recovery) plant, electrowinning, and doré casting. The report includes process design specifications, actual 2020 operating data, and projections for 2021.
Processing route
Crushing and agglomeration
Ore from open pit and underground mines is delivered to an underground primary crusher that reduces ore to P80 150 mm. Crushed ore is conveyed to a surface stockpile, then fed via apron feeders to the secondary-tertiary crushing circuit. Ore is screened on secondary screens, with oversize fed to the secondary crusher. Secondary crusher product feeds tertiary crushers closed by tertiary screens. Screen undersize at P80 25 mm is conveyed to the heap leach pad. Cement is added to the ore on the loading conveyor for agglomeration of fines, with mixing occurring during conveyor transfers.
Heap leaching
Ore is stacked on the heap leach pad in lifts using a conveyor stacker. Cyanide leach solution is distributed over the ore through pipelines and drip emitter tubing. Solution percolates through the ore, dissolving gold, and is collected on the pad liner, then transferred by gravity in lined channels to the pregnant solution pond.
ADR and gold recovery
Pregnant solution is pumped through carbon columns in series to adsorb gold onto carbon. Barren solution flows to the barren solution pond for reagent addition and reuse. Loaded carbon is transferred to an acid wash column where hydrochloric acid removes carbonate scale and impurities. Washed carbon is transferred to elution columns where a heated cyanide and caustic solution strips gold from the carbon. The gold cyanide solution passes through electrowinning cells to produce a gold-rich sludge. Sludge is washed, filtered, retorted to recover mercury, melted in a furnace, and cast into gold doré ingots for shipment to a refinery.
Planned improvements
Sustaining capital is planned to further automate the ADR plant and to recover carbon fines generated in the process, treating them to reduce possible gold loss.
Key reported parameters
| Parameter | Value | Basis |
|---|---|---|
| Plant design throughput | 25,000 tpd | Design |
| Primary crusher product size | P80 150 mm | Design |
| Final crush product size | P80 25 mm | Design |
| Ore crushed and placed in 2020 | 2,128,579 t | Actual |
| Average grade of ore placed in 2020 | 1.47 g/t Au | Actual |
| Gold ounces placed in 2020 | 100,623 oz Au | Actual |
| Gold production from mined and placed ore in 2020 | 59,359 oz Au | Actual |
| Annual gold recovery from placed ore in 2020 | 59% | Actual |
| Total gold production in 2020 | 72,823 oz Au | Actual |
| Total recovery vs ounces placed in 2020 | 72.4% | Actual |
| Cumulative ore placed to December 31, 2020 | 73,299,860 t | Actual |
| Cumulative average grade placed | 1.07 g/t Au | Actual |
| Cumulative gold ounces placed | 2,519,641 oz Au | Actual |
| Cumulative gold ounces recovered | 1,648,766 oz Au | Actual |
| Cumulative recovery | 65.4% | Actual |
| 2021 projected ore crushed and placed | 1,805,532 t | Forecast |
| 2021 projected grade | 1.48 g/t Au | Forecast |
| 2021 projected gold ounces placed | 85,851 oz Au | Forecast |
| 2021 projected gold production | 50,344 oz Au | Forecast |
| 2021 projected annual gold recovery | 58.6% | Forecast |
| 2021 projected total gold production | 62,293 oz Au | Forecast |
| 2021 projected total recovery vs ounces placed | 72.4% | Forecast |
| Estimated gold from secondary rinsing and leaching | 71,000 oz Au (2.9% of placed) | Testwork estimate |
| Gold included in cash flow model under retreatment (2021–2024) | 69,489 oz Au | Forecast |
| Average variable operating cost per tonne placed (2016–2020) | US$6.14/t (oxide) | Actual |
| Average variable operating cost per tonne placed (sulphide) | US$8.14/t | Actual |
| Average process operating cost per tonne placed (Jan–Jun 2021) | US$24.66/t | Actual |
| Average variable process cost per tonne placed (Jan–Jun 2021) | US$15.66/t | Actual |
| Average total process cost per gold ounce produced (Jan–Jun 2021) | US$459.86/oz Au | Actual |
| Average variable process cost per gold ounce produced (Jan–Jun 2021) | US$292.05/oz Au | Actual |
Project website: https://www.mineros.com.co/news/mineros-announces-execution-of-binding-agreement-to-sell-gualcamayo-property
Technical qualifications
Metallurgical testing continues to evaluate the feasibility of in situ secondary leaching of ore from the Valle Norte and Valle Sur heaps. The results of this testwork and estimates of material quantities indicate that approximately 71,000 oz Au, or approximately 2.9% of gold ounces placed, can be recovered from secondary rinsing and leaching. The cash flow model includes 69,489 oz Au to be recovered from 2021 through 2024 under the line-item Inventory WIP Pile Retreatment 1500, with 1500 referring to additional pumping capacity added for the retreatment process.
*Source: Gualcamayo Property , 2021 Technical Report, NI 43-101, Section 17.0 Recovery Methods, September 15, 2021.*
