Pueblo Viejo Refractory Gold Processing: Flotation, POX and CIL

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Pueblo Viejo is a large open-pit refractory gold-silver operation in the Dominican Republic. Its processing plant uses grinding, sulphide flotation, pressure oxidation (POX) and carbon-in-leach (CIL) recovery. This profile consolidates MillMatters’ previous Pueblo Viejo flowsheet summaries and separates the original whole-ore POX design from the expanded 14 Mt/a flowsheet described in the 2023 and 2026 technical reports.

Pueblo Viejo simplified process flowsheet, reproduced from Barrick 2025 technical report Figure 17-1.
Pueblo Viejo simplified process flowsheet, reproduced from Barrick 2025 technical report Figure 17-1. Source: technical report.
Operator and ownership Pueblo Viejo Dominicana; Barrick operates and owns 60%, with Newmont owning 40%
Location Dominican Republic
Commodities Gold and silver; copper has also been recovered as a by-product
Mine type Open pit, with stockpiled ore also included in the plant feed plan
Original plant route Crushing, SABC grinding, whole-ore POX, hot cure, CCD washing, lime boil and CIL
Expanded plant route Parallel grinding, sulphide flotation, POX of sulphide-bearing feed, separate POX-discharge and flotation-tailings CIL circuits
Original design basis 24,000 t/d, approximately 8.6 Mt/a
Expanded design capacity Approximately 14 Mt/a
Profile last reviewed August 30, 2026

Pueblo Viejo processing flowsheet

Pueblo Viejo treats refractory sulphide ore in which much of the gold and silver is not directly accessible to cyanide. The circuit therefore oxidizes sulphide minerals before final cyanidation. The expanded flowsheet adds flotation so that the sulphide-rich fraction can be directed to the oxygen- and autoclave-intensive POX circuit, while flotation tailings receive their own CIL treatment.

1. Primary crushing and ore storage

Run-of-mine and stockpiled ore are reduced by two primary gyratory-crusher systems. Technical records describe nominal crusher capacities of approximately 1,645 t/h and 3,000 t/h, with crushed product near a P80 of 130 mm. Conveyors deliver the product to coarse-ore storage ahead of the two grinding routes.

2. Parallel SABC and single-stage SAG grinding

The original SABC line combines a 9 MW SAG mill, pebble crushing and a 16.4 MW ball mill. The expansion added a 23 MW single-stage SAG (SS-SAG) line in parallel. Screens, pebble crushers and hydrocyclones control both circuits, producing a combined product near a P80 of 75 µm for downstream processing. The parallel arrangement increases throughput without replacing the original line.

3. Sulphide flotation

Two parallel flotation trains treat part of the cyclone overflow. Each train includes conditioning and five approximately 600 m³ rougher cells. PAX collector and copper sulphate activator promote sulphide recovery; guar gum and MIBC are used as depressant and frother. The sulphide-rich stream is combined with the portion of ground ore selected for POX treatment and thickened to roughly 50% solids. Flotation tailings bypass the autoclaves and report to the dedicated flotation-tailings CIL circuit.

4. Pressure oxidation

Four parallel autoclaves oxidize the refractory sulphides at approximately 225°C and 3,100 kPag, with a nominal retention time of about 60 minutes. Oxygen is supplied by dedicated onsite plants. Earlier reports describe operating conditions up to approximately 230°C and 3,450 kPa; these values belong to different design and reporting bases rather than to separate Pueblo Viejo plants.

5. Hot cure, CCD washing and lime boil

Autoclave discharge is flash-cooled and retained in hot-cure tanks above 90°C for approximately 12 hours. Hot curing helps dissolve basic ferric sulphate formed during POX. Three-stage counter-current decantation then washes acid and soluble metal sulphates from the oxidized solids. The washed solids are reheated to approximately 95°C and treated with lime for about 4.5 hours to decompose jarosite and improve silver liberation before cyanidation.

6. Dual carbon-in-leach recovery

The POX-discharge CIL (PDCIL) circuit contains 11 agitated tanks. A separate flotation-tailings CIL (FTCIL) circuit contains five tanks and recovers cyanide-soluble metal from material that does not require pressure oxidation. Activated carbon moves counter-current to slurry in both circuits. Loaded carbon is screened and transferred to the common recovery plant.

7. Elution, electrowinning and refining

Loaded carbon is acid-washed and stripped using Zadra elution. Gold and silver are recovered from pregnant solution by electrowinning. The resulting sludge is dried and retorted to remove mercury, then fluxed and smelted to produce doré. Stripped carbon is thermally regenerated and returned to the adsorption circuits.

Principal equipment and reported operating data

Area Equipment or parameter Reported value
Plant throughput Expanded design basis Approximately 14 Mt/a
Primary crushing Two gyratory-crusher systems Approximately 1,645 t/h and 3,000 t/h; product P80 near 130 mm
Original grinding line SABC circuit 9 MW SAG mill and 16.4 MW ball mill, with pebble crushing
Expansion grinding line Single-stage SAG circuit 23 MW SS-SAG mill
Grinding product Combined circuit target P80 approximately 75 µm
Flotation Two parallel rougher trains Five approximately 600 m³ cells per train
Pressure oxidation Four autoclaves Approximately 225°C, 3,100 kPag and 60 minutes
Hot cure Agitated retention More than 90°C for approximately 12 hours
CCD washing Counter-current decantation Three stages
Lime boil Jarosite treatment Approximately 95°C for 4.5 hours
Cyanidation PDCIL and FTCIL 11 tanks and five tanks, respectively
Full-capacity power Site processing demand Approximately 210 MW; the 2026 report basis cites 124.2 kWh/t

These figures summarize technical-report design and operating bases. They should not all be interpreted as simultaneous, demonstrated production results.

How the expansion changed the circuit

The original 24,000 t/d plant sent the ground refractory ore through whole-ore POX, followed by CIL. The expansion was designed to raise capacity toward 14 Mt/a and make lower-grade ore economic by adding a second primary crusher, the 23 MW SS-SAG line, flotation, a dedicated FTCIL circuit, additional oxygen capacity and autoclave flash-recycle thickening.

The central process change is selective use of the autoclaves. Flotation concentrates sulphide minerals and their associated refractory gold into the feed requiring oxidation. Flotation tailings can be cyanided separately. This helps use existing POX capacity more effectively while the two grinding routes increase the amount of ore available to the plant.

The 14 Mt/a figure is an expanded design basis, not a claim that every annual period has operated continuously at that rate. Likewise, the broader Pueblo Viejo life-extension program includes the Naranjo tailings-storage project and associated water-management work. Barrick’s 2026 updates describe that infrastructure program as ongoing, even though key processing-plant additions have been installed.

What changed between the technical reports?

Report period Plant position Material change or conclusion
2012 Project under construction The design used four autoclaves and whole-ore POX/CIL at 24,000 t/d. Forecast gold recovery of 88–95% was a design expectation, not yet sustained operating performance.
2014 Original process basis documented The report described SABC grinding, POX near 230°C and 3,450 kPa, hot cure, CCD, lime boil, CIL and hydrogen-sulphide copper precipitation.
2018 Operating plant The same 24,000 t/d whole-ore POX/CIL architecture was documented as an established operation, including Zadra elution, electrowinning, reagent plants and environmental controls.
2023 Expansion approved and being implemented The design basis increased from approximately 8.6 Mt/a to 14 Mt/a. Major additions included a new crusher, 23 MW SS-SAG mill, sulphide flotation, FTCIL, oxygen upgrades and autoclave flash-recycle thickening.
2026 Expanded process configuration documented The report describes the integrated parallel-grinding, flotation, POX and dual-CIL flowsheet at a 14 Mt/a design basis, alongside the continuing tailings and life-extension program.

Reagents, water and environmental controls

Pueblo Viejo’s refractory-ore route requires unusually large supporting systems. Dedicated oxygen plants serve the autoclaves and downstream processes. Onsite limestone and lime preparation supplies neutralization, lime boil, grinding and effluent-treatment demand. Technical records cite combined high-purity oxygen requirements near 7,000 t/d at the expanded design basis and substantial limestone consumption because POX generates acidic, metal-bearing solutions.

High-density-sludge neutralization precipitates dissolved metals from acidic process liquors. Tailings are treated by the INCO SO₂/air cyanide-destruction process with copper sulphate catalyst, and an effluent-treatment plant adjusts water quality before controlled discharge. Reclaim water is returned from tailings storage to reduce raw-water demand. These circuits are integral to the metallurgical flowsheet, not peripheral utilities: oxidation chemistry determines much of the site’s oxygen, lime, limestone, water and residue-management load.

Technical-report library and sources

Source period How it is used in this profile
2012 NI 43-101 technical report Original 24,000 t/d design, construction-stage plant configuration and forecast recovery range
2014 NI 43-101 technical report Whole-ore POX design conditions, wash and lime-boil stages, CIL and copper recovery
2018 NI 43-101 technical report Operating-plant configuration and established supporting facilities
2023 NI 43-101 technical report Expansion rationale, 14 Mt/a design, parallel grinding, flotation, FTCIL and plant upgrades
2026 NI 43-101 technical report Updated expanded flowsheet, equipment capacities, utilities and current life-of-mine context

Additional resources and industry links

Mineral processing basics

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