Overview
The Björkdal gold processing plant, originally commissioned in 1989, has undergone numerous upgrades to increase throughput while maintaining gold recovery. The circuit combines crushing, grinding, gravity concentration, and flotation to produce multiple gold concentrates.
Key Process Stages
- Crushing Circuit: Three-stage crushing (primary jaw + secondary/tertiary cone crushers) to achieve P80 of 8mm
- Grinding Circuit: Parallel primary ball/rod mills (No.1 & No.2) with classifying screen, secondary ball mill (No.3) for regrinding
- Gravity Concentration: Rougher/cleaner spirals → shaking tables → Knelson concentrators → final cleaner tables producing 60% Au concentrate
- Flotation Circuit: SkimAir flash flotation → rougher/scavenger flotation → two-stage cleaning producing final concentrate
- Recent Upgrades: G-max cyclone battery (2021), ball mill conversion to grate discharge (2023), toe position measurement system (2024)
Critical Data
| Parameter | Value |
|---|---|
| Primary Grinding P80 | 560 µm |
| Primary Cyclone Underflow P80 | 800 µm |
| Secondary Ball Mill Discharge P80 | 475 µm |
| Primary Cyclone Overflow P80 | 230 µm |
| Flotation Cyclone Overflow P80 | 125 µm |
| Gravity Concentrate Grade | 60% Au |
| Middlings Grade | 1,500 g/t Au |
Historical Modifications
| Year | Modification |
|---|---|
| 1990 | 750 kW regrind mill installed |
| 1992 | Sala 6.6 m³ flotation cell added |
| 2005 | Knelson CD12 + 7.5 kWh regrind mill installed |
| 2009 | Knelson XD30 installed pre-flotation |
| 2013 | Reichert cones replaced by rougher spirals, SkimAir-240 installed |
| 2017 | Flotation expansion for increased capacity/recovery |
| 2018 | Mintek Expert Process Control System installed |
Planned Improvements
The recent conversion of Ball Mill 2 from overflow to grate discharge has shown significant grinding efficiency improvements, with further throughput gains expected. The new toe position measurement system (2024) will optimize mill performance.
Technical report and processing history
The following archived source profiles have been consolidated here to preserve the project’s processing history and study context.
Björkdal Gold Mine — 2025 Technical Report
Björkdal Gold Mine — 2025 Technical Report
| Company | Mandalay Resources Corporation |
| Date | 2025-03-28 |
| Region | Sweden |
| Commodities | Gold |
Executive Summary
This section of the NI 43-101 Technical Report details the recovery methods employed at the Björkdal Gold Mine. The processing plant, originally commissioned in 1987, has undergone continuous modifications to increase throughput and gold recovery. The current circuit includes primary, secondary, and tertiary crushing, followed by parallel primary ball and rod milling. The process incorporates gravity concentration using spirals, shaking tables, and Knelson centrifuges, followed by flotation using SkimAir and conventional cells. Recent modifications include mill conversion to grate discharge and the installation of a process control system.
The concentrator produces three gravity concentrates and a flotation concentrate. Ore is delivered to stockpiles and fed through a jaw crusher, then screened. Oversize is recirculated through cone crushers until minus 8 mm. The crushed ore is ground in ball and rod mills, classified, and sent to gravity circuits. Gravity tailings are returned to regrind mills. Flotation circuit includes rougher, scavenger, and cleaner stages. The flotation concentrate is thickened and filtered for shipment.
Processing Methods
- Crushing: Primary Jaw Crusher, Secondary/Tertiary Cone Crushers
- Milling: Primary Ball Mill, Primary Rod Mill, Secondary Ball Mill
- Gravity: Rougher/Cleaner Spirals, Shaking Tables, Knelson Centrifuges
- Flotation: SkimAir Flash Flotation, Conventional Rougher/Cleaner/Scavenger Cells
Website: https://alkres.com/projects/bjorkdal/
Report Date: 2025-03-28
Region: Sweden
Project Status:
Commodity: Gold
Throughput:
Mine Life:
Mine Type:
Ore type:
Björkdal Gold Mine — 2023 Technical Report
Björkdal Gold Mine — 2023 Technical Report
| Company | Mandalay Resources Corporation |
| Date | 2023-03-31 |
| Region | Sweden |
| Commodities | Gold |
| Mine Type | Underground |
| Throughput | 1.3 Mtpa |
| Status | Operating |
Executive Summary
The Björkdal Gold Mine processing plant, originally commissioned in 1987, has undergone significant modifications to increase throughput and maintain gold recovery. The current circuit includes primary, secondary, and tertiary crushing, followed by primary and secondary grinding, gravity concentration, and flotation. Recent upgrades include the installation of Knelson concentrators, flotation expansion, and process control systems.
The plant processes ore through a series of stockpiles and crushers before grinding in ball and rod mills. Gravity recovery utilizes spirals, shaking tables, and Knelson centrifuges, while flotation employs SkimAir and conventional cells. The flotation concentrate is thickened and filtered for shipment.
Future plans include a potential throughput increase from 1.3 Mtpa to 1.5 Mtpa and a study on converting the ball mill to grate discharge mode to improve grinding efficiency. Metallurgical accounting relies on gravity and flotation samples due to ore heterogeneity.
Website: https://alkres.com/projects/bjorkdal/
Report Date: 2023-03-31
Region: Sweden
Project Status: Operating
Commodity: Gold
Throughput: 1.3 Mtpa
Mine Life:
Mine Type: Underground
Ore type: Sulphide
Björkdal — 2021 Technical Report
Björkdal — 2021 Technical Report
| Company | Mandalay Resources |
| Mine | Björkdal |
| Date | 2021 |
| Region | Sweden |
| Commodities | Gold |
Executive Summary
This section of the NI 43-101 Technical Report details the recovery methods employed at the Björkdal concentrator, originally designed by Davy McKee in 1987 for Terra Mining. The processing circuit has undergone numerous modifications since construction with the primary objective of increasing plant throughput while maintaining gold recovery. Key upgrades include the installation of regrind mills, flotation cells, gravity concentration equipment such as Knelson concentrators, and the implementation of an Expert Process Control System by Mintek in 2018.
The current flowsheet includes primary, secondary, and tertiary crushing followed by primary and secondary grinding. The circuit utilizes a series of gravity concentration steps involving spirals, shaking tables, and Knelson concentrators to produce three gravity concentrates. The remaining slurry undergoes regrinding and flotation to produce a final flotation concentrate. The plant produces a gravity concentrate containing approximately 60% gold and middlings with a concentration of approximately 1,500 g/t Au.
Final products are dewatered in thickeners and filtered prior to shipment. The report highlights the integration of flash flotation using an Outotec SkimAir cell and the replacement of Reichert cones with rougher spirals in 2013. The facility remains operational with ongoing commissioning of process control systems as of 2021, demonstrating a mature and continuously optimized recovery operation.
Processing Profile
Website: https://alkres.com/projects/bjorkdal/
Report Date: 2021
Region: Sweden
Project Status:
Commodity: Gold
Throughput:
Mine Life:
Mine Type:
Ore type:
Björkdal Gold Mine — 2021 Technical Report
Björkdal Gold Mine — 2021 Technical Report
| Company | Mandalay Resources Corporation |
| Mine | Björkdal Gold Mine |
| Date | 2021-03-26 |
| Region | Sweden |
| Commodities | Gold |
Executive Summary
This section of the NI 43-101 Technical Report details the recovery methods employed at the Björkdal Gold Mine, operated by Mandalay Resources Corporation. The processing plant, originally designed by Davy McKee in 1987, has undergone significant modifications between 1989 and 2018 to increase throughput and maintain gold recovery. Key upgrades include the installation of regrind mills, flotation cells, sorting plants, and gravity concentration equipment such as Knelson concentrators and spirals.
The concentrator circuit involves primary, secondary, and tertiary crushing followed by primary and secondary grinding. The ore is processed through a series of gravity concentration steps, including rougher and cleaner spirals, shaking tables, and Knelson centrifugal gravity concentrators. The gravity concentrates are produced alongside a flotation concentrate, which is dewatered and filtered prior to shipment.
The flotation circuit utilizes SkimAir flash flotation cells and conventional rougher, scavenger, and cleaner flotation cells. The process flowsheet is designed to handle various ore types through stockpiling campaigns for reconciliation. The plant status is operating, with recent commissioning of an Expert Process Control System in 2018 to optimize performance.
Reports
- reports/2021_Mandalay_Bjorkdal
Website: https://alkres.com/projects/bjorkdal/
Report Date: 2021-03-26
Region: Sweden
Project Status:
Commodity: Gold
Throughput:
Mine Life:
Mine Type:
Ore type:
Björkdal Gold Mine — 2020 Technical Report
Björkdal Gold Mine — 2020 Technical Report
| Company | Mandalay Resources Corporation |
| Mine | Björkdal Gold Mine |
| Date | 2020-03-26 |
| Commodities | Gold |
Executive Summary
The Björkdal Gold Mine processing plant, originally designed and built by Davy McKee in 1987 for Terra Mining, has undergone significant modifications to increase plant throughput while maintaining gold recovery. The facility utilizes a comprehensive circuit including primary, secondary, and tertiary crushing, primary and secondary grinding, gravity concentration steps, regrinding, and flotation to produce three gravity concentrates and a flotation concentrate. Major upgrades between 1989 and 2018 included the installation of regrind mills, Knelson concentrators, flotation expansion, and an Expert Process Control System.
The processing circuit begins with ore delivered to stockpiles and fed to a jaw crusher, followed by secondary and tertiary cone crushers to achieve a product size of minus 8 mm. The crushed ore is ground in parallel primary ball and rod mills, with classification managed by hydrocyclones and classifying screens. Gravity recovery is achieved through rougher and cleaner spirals, shaking tables, and Knelson centrifugal gravity concentrators, with the gravity concentrate containing approximately 60% gold.
Flotation is conducted using SkimAir flash flotation cells and conventional rougher, scavenger, and cleaner flotation cells. The flotation concentrate is dewatered in a thickener and filtered prior to shipment. The plant status is operating, with the most recent control system commissioning ongoing as of 2018. The report provides a detailed flowsheet and history of plant modifications to support operational reconciliation and recovery data.
Website: https://alkres.com/projects/bjorkdal/
Report Date: 2020-03-26
Region:
Project Status:
Commodity: Gold
Throughput:
Mine Life:
Mine Type:
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Björkdal Mine — 2018 Technical Report
Björkdal Mine — 2018 Technical Report
| Company | Mandalay Resources Corporation |
| Mine | Björkdal Mine |
| Date | 2018 |
| Commodities | Gold |
Executive Summary
The Björkdal Mine, operated by Mandalay Resources Corporation, has undergone significant processing modifications since its commissioning in 1987 to enhance throughput and gold recovery. The plant utilizes a multi-stage approach incorporating crushing, multi-stage grinding, and extensive gravity concentration followed by a flotation circuit to optimize the recovery of gold from the ore.
The processing facility features primary, secondary, and tertiary crushing, feeding into a primary ball and rod mill circuit. Gravity recovery is highly sophisticated, involving rougher/cleaner spirals, shaking tables, and Knelson centrifugal concentrators. The remaining material undergoes flash flotation via SkimAir cells and conventional rougher, scavenger, and cleaner flotation circuits to produce a final flotation concentrate for shipment.
Website: https://alkres.com/projects/bjorkdal/
Report Date: 2018
Region:
Project Status:
Commodity: Gold
Throughput:
Mine Life:
Mine Type:
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Björkdal Gold Mine — 2013 Technical Report
Björkdal Gold Mine — 2013 Technical Report
| Company | Gold-Ore / Elgin |
| Date | 2013 |
| Region | Sweden |
| Commodities | Gold |
| Throughput | 1.274 Mtpa |
| Status | Operating |
Executive Summary
The Björkdal plant, constructed by Davy McKee (UK), utilizes conventional crushing and grinding followed by a combination of gravity and flotation processing techniques to recover gold to four separate concentrates. Production commenced in 1988 and increased to reach a maximum throughput of 1.32 Mtpa in 1998. No ore was treated from July 1999 through September 2001 due to a period of bankruptcy of the previous operator. Production re-commenced in September 2001 and has been continuous since that time, with the plant producing its 1 millionth ounce in 2010. In 2012 the plant processed 1.274 million tonnes of ore.
The recovery circuit involves a three-stage crushing circuit using jaw and cone crushers, followed by grinding in rod and ball mills. Gravity recovery utilizes spiral separators, shaking tables, and Knelson concentrators to capture coarse gold. Flotation circuits use Sala and Outokumpu cells to recover fine gold, with final concentrate dewatering performed via thickening and vacuum drum filtration. The tailings are pumped to a tailings maintenance facility and are considered inert by the Swedish environmental authorities.
Website: https://portergeo.com.au/database/mineinfo.php?mineid=mn1221
Report Date: 2013
Region: Sweden
Project Status: Operating
Commodity: Gold
Throughput: 1.274 Mtpa
Mine Life:
Mine Type:
Ore type:
