The Maria Dama processing plant operates at 2,000 tpd capacity with a flowsheet incorporating crushing, grinding, gravity concentration, flotation, cyanidation, Merrill-Crowe precipitation, and polymetallic sulphide recovery.
Report context
This technical report is dated effective September 30, 2023 and describes the Segovia Operations located in Antioquia, Colombia. The report documents the recovery methods employed at the historical Maria Dama processing plant, which has been continually maintained and operational since mining began at Segovia and upgraded over the years to its current capacity. The process feed includes material mined by Aris Mining and partner-mining from within the Property titles, as well as material mined by smaller groups outside of the Property titles. Approximately 43% of production is sourced from partner mining.
Processing route
Crushing
Ore from owner operated mines is crushed to 15 mm in a two stage crushing circuit consisting of a 20 inch x 36 inch 150 horsepower (hp) jaw crusher that discharges to a crushed ore bin. The primary crushed ore is screened at 15 mm on a 1.9 m x 4.7 m double deck vibrating screen, with oversize conveyed to a 4 foot 200 hp secondary cone crusher and a 200 hp tertiary cone crusher operated in closed circuit with a secondary 1.8 m x 6.0 m vibrating screen. Another crushing line is available on standby, comprised of a 150 hp primary jaw crusher, two 200 hp secondary cone crushers, and two vibratory screens. The final crushed product is produced at 80% passing 7 mm, sampled with a primary cross-cut sampler and a secondary rotary sampler as it is conveyed to the fine ore bin. Samples are assayed by the Property's analytical laboratory.
Ore from partner operated mines does not require crushing and is dumped into a receiving bin, then sampled on a primary cross-cut sampler and a secondary rotary sampler and conveyed to a separate fine ore bin. Partner ore samples are assayed by an external commercial SGS laboratory.
Grinding and gravimetric concentration
The combined crushed owner and partner ore is conveyed on a single belt to a grinding circuit comprised of a 2,000 tonne per day capacity, 12.5 foot x 23 foot 2,300 hp ball mill operated in a closed circuit cluster of four hydrocyclones (with two on standby) to produce a final grind of 80% passing 106 microns, which advances to the flotation circuit. Half of the cyclone underflow is diverted to the gravity concentration circuit comprised of two 40 hp Knelson centrifugal concentrators, operating in closed circuit with the grinding circuit. Approximately 30% of the contained gold is recovered into a primary gravity concentrate, then upgraded on a Gemini table. The grinding circuit feed is continuously weighed on a belt scale and sampled every hour.
Flotation and regrind
Cyclone overflow from the grinding circuit advances to the flotation circuit for conditioning with flotation reagents. The conditioned slurry passes through one stage of rougher flotation in a 40 cubic metre tank cell, with the overflow passing to one 30 cubic metre cleaner cell and then three stages of scavenger flotation in three 30 cubic metre flotation cells to recover the contained gold. The rougher and scavenger flotation concentrate is upgraded in one stage of cleaner flotation and combined with the rougher flotation concentrate. The combined rougher and scavenger cleaner concentrate is thickened to around 55% solids and reground in a 4 foot x 8 foot 40 hp ball mill to approximately 80% passing 38 microns, then passed to the cyanidation circuit. The regrind ball mill is operated in closed circuit with 6 inch cyclones. The flotation tailings are pumped to the tailings storage facility where they are thickened and filtered to around 15% moisture prior to dry stack placement. The thickener overflow and filtrate solutions are recycled back from the tailings storage facility to the process plant.
Cyanidation and counter current decantation
The reground flotation concentrate is thickened and processed in a cyanidation circuit comprised of four agitated leach tanks operated in series for a total leach retention time of around 96 hours. The cyanide concentration is adjusted in the first leach tank and allowed to attenuate naturally in the last leach tank. The pH of the leach slurry is maintained at around 10.5 to 11 with the addition of lime. Discharge from the last agitated leach tank flows to the counter current decantation circuit, comprised of one 24 foot diameter thickener, two 16 foot diameter thickeners, and one 42 foot diameter thickener to wash the pregnant leach solution from the leach residue. The pregnant leach solution from the first thickener overflow advances to the Merrill-Crowe recovery circuit. The tails of the leaching process are detoxified using hydrogen peroxide and iron sulphate, then passed to the polymetallic concentrate processing plant.
Merrill-Crowe and refining
The solubilized gold and silver are recovered from the pregnant leach solution by clarifying the solution to remove any remaining suspended solids, de-aerating the solution to less than 1 ppm dissolved oxygen, and then precipitating the gold and silver with the addition of zinc dust. The gold and silver precipitate is recovered in three plate and frame pressure filters, then smelted with a flux in a gas fired furnace to produce the doré product. The gravity concentrate produced by the Gemini table is separately smelted with a flux in a gas fired furnace to produce a second doré product.
Polymetallic concentrate plant
A 200 tonne per day capacity polymetallic concentrate plant was constructed in 2021 to clean lead and zinc sulphides from the tailings generated by the Maria Dama processing plant. The tailings are passed to a five cubic metre conditioning tank in the lead circuit and treated with regulating reagents to depress sphalerite, pyrite, and insoluble materials. The tails proceed to a second five cubic metre conditioning tank treated with collectors that react with lead sulphides. Once conditioned, the pulp goes to a rougher stage consisting of a bank of four rougher cells with forced air that operate in parallel with a single scavenger feed cell where flotation begins. The flotation concentrates are taken to three cleaning cells with a total capacity of 1.2 cubic metres. The depleted tails then pass to the zinc circuit, and the recovered and cleaned lead concentrate from the cleaning stage is transported to the thickening area.
Zinc flotation takes place in a circuit similar to the lead flotation, starting with two stages of conditioning that activates the sphalerite depressed by the reagents in the lead circuit. Flotation begins in the rougher stage, then the flotation concentrates are taken to the cleaner and scavenger stage, and the final tails are pumped to the tailings filtration plant at the dry stack tailings facility.
The lead and zinc concentrates are pumped to separate thickeners to obtain a solids percentage of around 55 to 65%, then discharged to a lead or zinc homogenizer tank used as a pre-filtration stage, then pumped to separate hydraulic filter presses. The dried lead and zinc concentrates are separately packed in 1,000 kg capacity bags and stored in a warehouse prior to shipment to the concentrate buyer. The first concentrate was exported in December 2022.
Power, water, and process material requirements
The Property consumes a total of 100.5 GWh annually from public and private power producers. The processing plants require 47.0 litres of water per second for an annual consumption of 1.5 million cubic metres, sourced from underground dewatering and rainwater runoff stored in a surface pond near the Maria Dama processing plant. Reagent and grinding ball use includes mineral activators, frother, and collector in the flotation circuit, flocculants in the thickening circuit, sodium cyanide and lime in the cyanidation circuit, zinc dust in the Merrill-Crowe circuit, hydrogen peroxide in the cyanide detoxification circuit, a variety of fluxes in the refinery, grinding balls in the primary grinding and regrind circuit, and other standard processing chemicals.
Recommendations
An opportunity exists to increase the capacity of the Maria Dama processing plant from 2,000 to 3,000 tpd by utilizing a previously purchased ball mill already located at the Property, and by relocating and upgrading the facilities that receive material from the Segovia Operations' artisanal and small scale mining partners. This creates the potential to gradually increase annual gold production from 200,000 to 300,000 ounces of gold by filling the extra capacity by increasing mining rates. A portion of the extra capacity may be allocated to the Segovia Operations' artisanal and small scale mining partners. The addition of the ball mill to the existing circuit would enable both higher throughput and more effective use of available capacity, thereby enhancing the overall gold recovery rate for all processed materials. An upgraded receiving facility for partner mined material could also be designed to increase volumes and efficiencies. This small-scope project could be completed by early 2025 at an estimated cost of US$11.0 million.
Key reported parameters
| Parameter | Value | Units | Basis |
|---|---|---|---|
| Maria Dama plant capacity | 2,000 | tpd | Historical operating |
| Crushed product size | 80% passing 7 | mm | Design |
| Grind size (primary) | 80% passing 106 | microns | Design |
| Regrind size | 80% passing 38 | microns | Design |
| Ball mill power (primary) | 2,300 | hp | Design |
| Ball mill dimensions (primary) | 12.5 x 23 | foot | Design |
| Gravity gold recovery | 30 | % | Historical operating |
| Leach retention time | 96 | hours | Design |
| Leach pH | 10.5 to 11 | , | Design |
| Polymetallic plant capacity | 200 | tpd | Design |
| Concentrate solids (polymetallic) | 55 to 65 | % | Design |
| Tailings moisture (dry stack) | 15 | % | Design |
| Annual power consumption | 100.5 | GWh | Historical operating |
| Water consumption | 47.0 | litres/second | Historical operating |
| Annual water consumption | 1.5 | million cubic metres | Historical operating |
| Partner mining production share | 43 | % | Historical operating |
| Proposed capacity expansion | 3,000 | tpd | Proposed design |
| Proposed annual gold production increase | 200,000 to 300,000 | ounces | Proposed design |
| Expansion estimated cost | US$11.0 | million | Proposed design |
| Expansion completion target | Early 2025 | , | Proposed design |
Project website: https://aris-mining.com/operation/segovia/
Project website: https://digbee.com/organisation/401-bay-street-suite-2400-po-box-15-toronto-on-m5h-2y4/overview
Technical qualifications
The technical report specifies that the qualified person responsible for Section 17 (Recovery Methods) recommends implementing the small-scope capacity expansion project. The report does not provide testwork results for the proposed expansion, nor does it include detailed mass balances, metallurgical recoveries, or equipment sizing calculations for the upgraded circuit. The historical operating data for the Maria Dama plant is presented as descriptive information without supporting testwork or performance data for individual unit operations. The polymetallic concentrate plant is described as constructed in 2021, with the first concentrate exported in December 2022, but no operational performance data or metallurgical testwork results are provided for this circuit.
Source: NI 43-101 Technical Report for the Segovia Operations, Antioquia, Colombia, effective September 30, 2023, Section 17 Recovery methods.
