The Gramalote Project is a gold deposit in Colombia for which a 2025 Feasibility Study has defined a proposed processing plant design based on comminution, flotation, and carbon-in-pulp leaching.
Report context
This technical report, dated August 2025, presents the results of a feasibility study for the Gramalote Project in Colombia. The processing plant described is a proposed design based on metallurgical testwork and modelling optimization studies. The report specifies that the plant design uses a flowsheet of well-proven unit operations, and that key design criteria include a throughput of 6 Mt/a and a process plant availability of 92%.
Processing route
Comminution circuit
The proposed plant design commences with single-stage primary crushing using a gyratory crusher to produce a crushed product size of 80% passing (P80) 150 mm. Crushed ore is stored in a stockpile with a nominal 21,000 t live capacity, providing 15 hours of operation at design throughput. During extended primary crusher maintenance periods of up to three days, ore from the dead portion of the stockpile will be reclaimed by an excavator or dozer to feed the downstream circuit. Apron feeders positioned under the stockpile reclaim ore for the secondary crushing circuit.
Closed circuit secondary crushing using duty/stand-by cone crushers is designed to produce a crushed product P80 of approximately 27 mm. This feed size preparation is specified for an HPGR-ball mill circuit. The HPGR will operate in closed circuit with wet sizing screens, with undersize slurry reporting to the milling circuit via a cyclone feed pumpbox. A ball mill in closed circuit with hydrocyclones is designed to produce a P80 grind size of 250 µm. Cyclone overflow will flow by gravity to the flotation circuit.
Gravity and flotation circuits
A gravity gold recovery circuit, included based on metallurgical testwork results and a modelling optimization study, will contain two centrifugal gravity concentrators and an intensive cyanidation leach reactor.
The flotation circuit design includes five flotation cells arranged in series, using a simple collector (PAX) and frother reagent addition scheme. The cells can be operated in rougher only, or a rougher/scavenger flowsheet if higher concentrate grades or lower mass recoveries need to be targeted. The rougher-only flowsheet is anticipated as the primary operating method.
Flotation concentrate will be pumped to a flotation concentrate thickener ahead of a regrind circuit. The thickener provides a buffer between the primary grinding and flotation circuits and the regrind mill, controls water balance, and helps break down froth. The regrind circuit includes a trash screen and a regrind mill in closed circuit with hydrocyclones. The cyclone overflow product size of P80 20 µm is expected with a low cyclone overflow slurry density of 15% solids (w/w) to promote better classification efficiency. Cyclone overflow will flow by gravity to the pre-leach thickener.
Leach and carbon-in-pulp circuit
A pre-leach thickener is included to increase the slurry density of the finely ground flotation concentrate stream to the leach circuit, minimising slurry tank volume requirements and reducing overall reagent consumption.
The pre-aeration and leach circuit design consists of six tanks, providing 6 hours of pre-aeration and 30 hours of leaching residence time at design plant throughput. Slaked lime slurry will be added for pH adjustment. Sodium cyanide solution is added to start gold leaching in the presence of elevated dissolved oxygen and lead nitrate solution.
A carbon-in-pulp (CIP) circuit will consist of six stages of carbon adsorption for recovery of dissolved gold. A Pressure Zadra elution circuit will be used to recover gold to doré. The circuit includes an acid wash column to remove inorganic foulants from the carbon with hydrochloric acid. A carbon regeneration kiln is included to remove organic foulants, including any residual flotation circuit reagents, from the carbon with heat.
Cyanide destruction and tailings
A cyanide destruction circuit using SO2 and air is designed to reduce the weakly-acid dissociable cyanide concentration in the flotation concentrate leach tailings discharge stream to an environmentally acceptable level.
A flotation tailings thickener is included in the design to increase slurry density for water recovery prior to tailings discharge to the tailings management facility (TMF). The TMF will store both flotation and leach circuit cyanide destruction tailing streams, which will be separately handled and deposited. The tailings material contains a high percentage of a sand-forming coarse fraction, planned to be placed directly downstream of the starter dam.
Infrastructure and utilities
The process plant will use process water, leach water, reclaim water, fresh water, treated water, gland water, and potable water. Make-up water for process and leach water will be pumped from the reclaim water pond, which receives water recovered from tailings decant pumps at the TMF. Water from thickener overflow streams will be recycled. Approximately 1,200 m³/h of decant return water will be recycled from the TMF to the process plant, with approximately 56 m³/h of fresh water required as make-up from Guacas Creek.
Power is planned from gas-based self-generation, with the project located 2 km from a main gas pipeline. The power plant will consist of four gas-powered engines with a total installed capacity of about 44 MW, sufficient for peak Project demands of about 30 MW, operating three engines with one on stand-by.
Major reagents specified for the process plant include slaked lime, PAX collector, frother, sodium cyanide, lead nitrate, caustic soda, hydrochloric acid, sodium metabisulphite, copper sulphate pentahydrate, flocculant, anti-scalant, fluxes, and diesel fuel.
Key reported parameters
| Parameter | Value | Basis |
|---|---|---|
| Plant throughput | 6 Mt/a | Design assumption |
| Crushed product size (primary) | P80 150 mm | Design specification |
| Secondary crushed product size | P80 approx. 27 mm | Design specification |
| Ball mill grind size | P80 250 µm | Design specification |
| Regrind product size | P80 20 µm | Design expectation |
| Flotation mass pull design margin | 5% (expected 3%) | Design criterion |
| Process plant availability | 92% | Design assumption |
| Crushed ore stockpile live capacity | 21,000 t | Design specification |
| Number of flotation cells | 5 | Design configuration |
| Pre-aeration residence time | 6 hours | Design residence time |
| Leach residence time | 30 hours | Design residence time |
| Number of CIP stages | 6 | Design specification |
| TMF capacity (proposed storage) | 76.7 Mt | Over 13-year processing period |
| TMF capacity (approved) | 220 Mt | 2016 approval, part of current EIA |
| Plant power demand | approx. 238,649,287 kW/a | Design estimate |
| Power plant installed capacity | approx. 44 MW | Proposed design |
| Peak Project demand | approx. 30 MW | Design estimate |
| Recycled water from TMF | approx. 1,200 m³/h | Design estimate |
| Fresh water make-up | approx. 56 m³/h | Design estimate from Guacas Creek |
| Closure cost estimate | approx. US$51.2 million | B2Gold estimate |
Project website: https://www.b2gold.com/operations-projects/development/gramalote-project-colombia/default.aspx
Technical qualifications
This report presents a proposed plant design based on a feasibility study dated August 2025. The design is based on metallurgical testwork results and modelling optimization studies, as stated in the report. The facility has not been constructed at the report date, and all parameters described represent design specifications, assumptions, or expectations. No historical operating data for this processing plant are reported, as the project is at the feasibility stage. The TMF capacity of 220 Mt was approved in 2016 and is part of the current Environmental Impact Assessment (EIA). An updated Modified EIA showing the 2025 Feasibility Study is planned for submission.
Source: Gramalote Project, Colombia, NI 43-101 Technical Report, August 2025, Sections 1.15, 1.16, 1.17.
