Continental Gold's March 2019 Buriticá mineral resource report, effective January 30, 2019, carries forward the recovery methods of the 2016 feasibility study for the underground gold project in Antioquia, Colombia, without change.
The NI 43-101 Buriticá Mineral Resource 2019-01 report for Continental Gold Inc., covering the Buriticá project in Antioquia, Colombia, has an effective date of January 30, 2019 and a report date of March 18, 2019. Its recovery methods section is taken from the 2016 Buriticá Feasibility Study by JDS, effective February 24, 2016. The report states that no new metallurgical testwork has been done since then, so the plant design is unchanged. The 2019 resource covers the same deposits, with mostly infill drilling added in the planned mining areas.
Critical Data
| Parameter | Value | Unit | Notes |
|---|---|---|---|
| Report effective date | January 30, 2019 | Not applicable | Recovery methods from the 2016 JDS feasibility study |
| Design throughput | 3,000 | t/d | 1,095,000 t/a at 91% availability, 365 d/a |
| Design head grade | 8.5 g/t Au, 24.2 g/t Ag | Not applicable | Not applicable |
| Gravity recovery | 40 to 90 | % | Range in the production schedule table |
| Primary crusher | Jaw, F100 357 mm to P80 150 mm | Not applicable | 14,000 t ROM stockpile |
| Coarse ore stockpile | 3,400 t live, 5,400 t total | Not applicable | Covered |
| SAG mill | 5.8 m x 4.2 m (3.8 m EGL), 2,000 kW VSD | Not applicable | Closed with screen and pebble crusher |
| Grind | P80 74 | µm | Ball mill with hydrocyclones |
| CCD | Four stages | Not applicable | Ahead of Merrill-Crowe |
| Bond work index (75th percentile) | 19.54 rod, 17.2 ball | kWh/t | Crushing work index 13.6 kWh/t |
| Metal production | 284,000 oz/a Au, 503,000 oz/a Ag | Not applicable | Process mass balance |
Overview
The process runs crushing, grinding, gravity concentration, cyanide leaching, countercurrent decantation (CCD), Merrill-Crowe and on-site refining to doré. Tailings are filtered before disposal in a lined facility, and process water is recycled to minimize consumption. A MetSim mass balance, based on the completed testwork, gives metal production of about 284,000 oz of gold and 503,000 oz of silver a year.
Key Process Stages
Crushing. Underground ore is trucked in 30 and 40 t trucks to a 14,000 t ROM stockpile for blending. A front-end loader feeds a stationary grizzly over the dump hopper, with a mobile rock breaker for oversize. An apron feeder feeds a jaw crusher, which takes ore from F100 357 mm to P80 150 mm, onto the conveyor to the covered coarse ore stockpile.
Reclaim. Two reclaim feeders (one standby), each 137 t/h nominal and 250 t/h maximum, feed the mill conveyor. Cement is added dry on the conveyor to provide alkalinity for leaching.
Grinding. A 5.8 m by 4.2 m SAG mill with a 2,000 kW variable-speed motor reduces the ore from 150 mm to about 2 mm in closed circuit with a vibrating screen and pebble crusher. A ball mill closed with hydrocyclones grinds to P80 74 µm.
Gravity. Combined SAG and ball mill discharge is split to two high-capacity centrifugal concentrators, each behind a scalping screen. The concentrate is upgraded by a magnetic separator and a concentrating table to a product that can be refined directly. Table tails return to grinding.
Leaching and CCD. After a trash screen, the slurry is leached with cyanide and oxygen in agitated tanks, then washed in a four-stage CCD circuit.
Merrill-Crowe and refining. Gold and silver are precipitated from the pregnant solution with zinc dust. The precipitate and gravity concentrate are smelted with fluxes into gold-silver doré.
Cyanide recovery and destruction. Some cyanide is recovered in a thickener. Residual cyanide is oxidized with a sulphur compound and oxygen, and the soluble copper already in the leach tails is expected to make copper catalyst unnecessary.
Tailings. Oxidized slurry is thickened and filtered so that water returns to the process, and the filtered tailings go to a lined tailings storage facility.
Additional Interesting Data and Summary
The reagents handled on site are sodium cyanide, caustic soda, cement, calcium hydroxide, lead nitrate, flocculant, antiscalant, sodium metabisulphite, copper sulphate pentahydrate, diatomaceous earth, zinc dust and refinery fluxes. The section gives the design basis as both 1,095,000 t a year (3,000 t/d over 365 days) and 1,200,000 dry t a year at 91% availability. This article uses the 3,000 t/d figure that both share.
In summary, Buriticá's design is a high-grade underground gold-silver plant at 3,000 t/d, in which gravity recovers a large share of the gold ahead of leaching, CCD and Merrill-Crowe, and all tailings are filtered and stored in a lined facility.
Key Processes
- Jaw crushing and covered coarse ore stockpile
- SAG milling with pebble crushing and ball milling to P80 74 µm
- Centrifugal gravity concentration with magnetic separation and tabling
- Cyanide leaching with oxygen
- Four-stage countercurrent decantation
- Merrill-Crowe zinc precipitation and smelting to doré
- Cyanide recovery and oxidation
- Tailings thickening, filtration and lined storage
Source: Continental Gold, NI 43-101 Buriticá Mineral Resource 2019-01, Antioquia, Colombia, effective date January 30, 2019 (recovery methods from the 2016 Buriticá Feasibility Study, JDS).
Earlier report summaries
Earlier versions of this profile, based on older technical reports, are retained below for source traceability. Dates and figures reflect each report’s own effective date and are superseded by the current information above.
Buriticá Gold Project — 2015 Technical Report
This technical report presents a mineral resource estimate for the Yaraguá and Veta Sur vein systems at the Buriticá Gold Project in Colombia, supported by proposed processing routes from a 2014 preliminary economic assessment.
Report context
The Buriticá Gold Project is located approximately 72 km northwest of Medellín, Colombia, and is 100% owned by Continental Gold Inc. through its wholly-owned subsidiary CGL Buritica Limited. The project comprises 66 granted tenements and applications covering approximately 61,783 ha. A preliminary economic assessment (PEA) effective November 17, 2014, and dated December 22, 2014, was prepared by M3 Engineering & Technology Corporation and forms the basis for the processing information reproduced in this 2015 technical report.
Processing route
Proposed plant throughput
The PEA assumes that the Buriticá Project will consist of an underground mine anticipated to provide a mill throughput of 2,000 tonnes per day (tpd) initially, later increasing to 3,500 tpd.
Proposed metallurgical process
Mineralized vein material comprising the resource will be leached with cyanide and recovered via a Merrill Crowe process. Gold/silver bullion will be produced on site.
Proposed tailings management
Tailings will be dry stacked.
Mine life
The mine life is approximately 18 years based on the 2014 resource estimates that informed the PEA.
Key reported parameters
| Parameter | Value | Basis |
|---|---|---|
| Initial mill throughput | 2,000 tpd | Proposed design (PEA) |
| Later mill throughput | 3,500 tpd | Proposed design (PEA) |
| Mine life | Approximately 18 years | Proposed design (2014 resource) |
| Gold recovery method | Cyanide leaching, Merrill Crowe | Proposed design (PEA) |
| Product | Gold/silver bullion | Proposed design (PEA) |
| Tailings method | Dry stacking | Proposed design (PEA) |
| Historical mine | Yaraguá underground gold mine | Historical operating data |
| Average mineralized interval | Approximately 1.1 metre true width | Historical underground development data |
Project website: https://www.continentalgold.com/continental-gold-limited-announces-internal-reorganization-2/
Technical qualifications
The technical information and economic parameters used in the PEA are considered relevant to the Buriticá Gold Project and are reproduced in this update report. Readers are referred to the cautionary note regarding the preliminary economic assessment contained in subsection 2.6 of the source report. This technical report includes updated mineral resource estimations for the Yaraguá and Veta Sur mineral systems. Underground work by CGI has been confined to exploration and development of the Yaraguá vein system and development of the primary mine access via the Higabra Valley Tunnel.
Source: Independent Technical Report and Resource Estimate on the Buriticá Gold Project 2015.
