Overview
Nestled in the historic goldfields of Victoria, Australia, the Costerfield Operation stands as a significant producer of critical antimony and gold. Operated by Mandalay Resources Costerfield Operations Pty Ltd., a subsidiary of the Toronto-based Mandalay Resources Corporation, this facility has been a cornerstone of the regional mining industry since its modern re-establishment in 2007. The operation processes a complex sulfide ore rich in antimony and gold through its Brunswick Processing Plant, a sophisticated concentrator that has undergone continuous improvement to optimize recoveries and throughput. Located approximately 120 kilometers north of Melbourne, the project leverages existing infrastructure in a well-established mining district. The strategic importance of the Costerfield Operation cannot be overstated—antimony is classified as a critical mineral by numerous governments due to its essential role in flame-retardants, lead-acid batteries, and military applications, while gold remains a premier precious metal. The facility’s ability to efficiently recover both commodities from a single ore body makes it a technically interesting and economically vital operation, demonstrating advanced mineral processing techniques that balance high recovery rates with operational efficiency and environmental stewardship.
Key Process Stages
The Brunswick Processing Plant employs a conventional yet highly optimized circuit designed specifically for antimony-gold sulfide ore. The process flowsheet incorporates crushing, grinding, gravity separation, and flotation, followed by concentrate dewatering and tailings management. The plant has demonstrated remarkable consistency, operating 24/7 with crushing activities limited to extended day shifts to comply with local noise restrictions. Recent upgrades, including the addition of advanced flotation technology, have positioned this operation at the forefront of modern mineral processing for critical minerals.
- Stage 1: Crushing and Screening The run-of-mine (ROM) ore is reduced in size through a two-stage crushing circuit. Primary crushing is handled by mobile Finlay I-130RS and I-140RS impact crushers in closed circuit with a 35 mm screen. The secondary crushing stage utilizes a Finlay C-1540RS mobile cone crusher operating in closed circuit with a 12 mm screen. The crushed product is stored in a 40-tonne fine ore bin, which is scheduled for replacement with a 1,500-tonne capacity reclaim feeder in 2025 to enhance feed consistency and capacity.
- Stage 2: Milling and Gravity Concentration The crushed ore is fed into a two-stage, closed-circuit ball milling operation. The primary mill operates in closed circuit with a Dutch State Mines (DSM) screen. The screen undersize is fed to centrifugal gravity concentrators to recover liberated gold particles. This gravity concentrate is further upgraded on a shaking table in a dedicated gold room, producing a high-grade gold product shipped directly to local refineries. Gravity recovery for gold is exceptionally high, typically achieving 55-65% and peaking at 70% of the total gold in feed.
- Stage 3: Flotation The cyclone overflow from the milling circuit, now at a target grind size of P80 53 µm, is conditioned with lead nitrate (activator) and potassium amyl xanthate, or PAX (collector). The pulp first reports to two 48-inch StackCell roughers, followed by two additional rougher tank cells. The rougher concentrate forms part of the final product. The tailings from these cells advance to the original Denver flotation train, consisting of eight DR100 rougher/scavenger cells and six DR15 cleaner cells. To enhance recovery from the tailings stream, rougher and cleaner CavTube column flotation cells were commissioned in April 2021, producing a separate low-grade concentrate and ensuring maximum antimony and residual gold extraction.
- Stage 4: Concentrate Dewatering The final concentrates from the main flotation circuit and the CavTube columns are pumped to two separate concentrate thickeners. The thickened underflows are dewatered using a plate and frame pressure filter. The filter cake is discharged into bags, which are then packed into shipping containers for export to international customers. All thickener overflows and filtrates are recycled back into the process circuit to maximize water efficiency and minimize metal losses.
- Stage 5: Tailings Management Flotation tailings are thickened to approximately 50% w/w solids. A significant portion of these tailings is used as underground paste fill, mixed with a cement binder in a pugmill and pumped back into old mine workings. The remaining tailings are deposited in the Tailings Storage Facilities (TSFs). A new TSF with a capacity of 788,000 dry metric tonnes is under construction and expected to be operational by May 2025. Water from the tailings thickener is decanted and recycled, contributing to the site’s high water reuse rate.
Critical Data
The following table summarizes the key operational and metallurgical performance data for the Brunswick Processing Plant, highlighting its efficiency and capacity.
| Parameter | Value | Unit | Notes |
|---|---|---|---|
| Throughput (Monthly Avg.) | 11,000 – 13,000 | dmt/month | Demonstrated capacity up to 14,000 dmt/month |
| Target Grind Size | 53 | µm (P80) | Achieved via two-stage ball milling circuit |
| Antimony Recovery (LoM Forecast) | 90.1 | % | Based on Youle & Shepherd ore blend algorithm |
| Gold Recovery (LoM Forecast) | 92.2 | % | Includes ~60% gravity recovery + flotation |
| Gold Gravity Recovery | 55 – 70 | % | Varies with feed blend; peak performance noted |
| Operating Schedule | 24/7 | hours/day | Crushing operates on extended day shift only |
| Water Reuse | High | – | Extensive recycling from thickeners and TSF |
| Make-up Water Source | 1.5 – 2.0 | ML/day | Primarily from underground dewatering |
Additional Interesting Data and Summary
The Costerfield Operation is a exemplar of modern, responsible mining, integrating technical innovation with stringent environmental and social governance (ESG) principles. A key feature of the site’s sustainability is its sophisticated water management system. The plant operates with a positive water balance due to continuous underground dewatering, producing 1.5 to 2 million liters of water per day. To manage this, a reverse osmosis (RO) plant with a capacity of 2 ML/day was installed in 2014, with a pre-treatment plant added in 2017 to enhance its reliability. Excess water is handled by the Splitters Creek evaporation facility, which has a net evaporation capacity of approximately 104 ML per year.
From a technical perspective, the operation has focused on continuous improvement through strategic debottlenecking and technology adoption. The 2021 installation of Eriez CavTube column flotation cells on the tailings stream is a prime example, designed to scavenge additional value and improve overall recovery, particularly important as the head grades from the Shepherd ore zone are typically lower. Power infrastructure was consolidated and upgraded in 2019 to increase efficiency and allow for the integration of backup diesel generation, ensuring operational resilience.
The economic impact of the operation is significant, providing stable employment in the region and contributing to the global supply of critical antimony. The future outlook remains positive, supported by a robust Life of Mine (LoM) plan and ongoing infrastructure investments, such as the new TSF and the fine ore bin upgrade. The processing plant’s flexibility and proven performance over its 14-year history suggest it is well-equipped to handle the planned ore feed blends for the foreseeable future, ensuring that the Costerfield Operation will remain a key player in the critical minerals market.
Source: NI 43-101 Technical Report | Date: March 2025
Further Reading
- https://alkres.com/projects/costerfield/
Technical report and processing history
The following archived source profiles have been consolidated here to preserve the project’s processing history and study context.
Costerfield Operation — 2025 Technical Report (Recovery Methods)
Costerfield Operation — 2025 Technical Report (Recovery Methods)
| Company | Mandalay Resources |
| Date | March 2025 |
| Region | Victoria, Australia |
| Commodities | Gold, Antimony |
Executive Summary
The Brunswick Processing Plant at the Costerfield Operation treats antimony and gold rich sulfide ore through a conventional comminution and flotation style concentrator. Operating since 2007 and managed by Mandalay Resources since late 2009, the plant has undergone several upgrades to increase production capacity to approximately 10,000–13,000 t/month over the 2015–2024 calendar years. The concentrator operates 24 hours per day, 7 days per week, utilizing a well-proven circuit suited to processing the Costerfield ores remaining in the Life of Mine plan.
The processing circuit involves surface crushing and screening followed by a two-stage, closed circuit ball milling circuit. Centrifugal style gravity concentrators are used to recover a gold-rich gravity concentrate, which is upgraded on a shaking table and sold as a separate product. Secondary milled products are processed through a flotation circuit comprising StackCell roughers, tank cells, and CavTube flotation columns added in 2021 to recover antimony and remaining gold.
The flotation concentrate is dewatered through thickeners and filtration to produce a final antimony-gold concentrate product shipped overseas. Forecast average LoM 2025 recoveries are 90.1% for antimony and 92.2% for gold. The plant maintains a positive water balance and utilizes paste fill for underground disposal of tailings where applicable.
Reports
Costerfield Operation — 2025 Technical Report
Costerfield Operation — 2025 Technical Report
| Company | Mandalay Resources |
| Date | 2025 |
| Region | Victoria, Australia |
| Commodities | Gold, Antimony |
Executive Summary
The Costerfield Operation in Victoria, Australia is an underground mining project currently operated by Mandalay Resources. The site features the Brunswick Processing Plant, which has been in operation since 2007 and has been managed by Mandalay since late 2009. The facility treats antimony and gold-rich sulfide ore using a conventional comminution and flotation concentrator. Recent plant upgrades have increased production capacity to approximately 10,000–13,000 dry metric tonnes per month.
The processing circuit involves a two-stage closed circuit ball milling process following surface crushing and screening. Crushed ore is processed through mobile impact and cone crushers before entering the milling circuit. Gravity concentration is employed using centrifugal style concentrators and shaking tables to recover a high-grade gold concentrate, which is sent to local refineries. The milling circuit targets a grind size P80 of 53 µm.
The flotation circuit is designed to recover an antimony-gold rich sulfide concentrate. It utilizes StackCell roughers, Denver DR100 and DR15 cells, and CavTube flotation columns added in 2021. The final concentrate is dewatered and shipped overseas, while tailings are thickened for use in tailings storage facilities or underground paste fill. The circuit is described as simple, conventional, and well-proven for the remaining life of mine plan.
Website: https://alkres.com/projects/costerfield/ Report Date: 2025 Region: Victoria, Australia Project Status: Commodity: Gold, Antimony Throughput: Mine Life: Mine Type: Ore type:Costerfield Operation — 2024 Technical Report
Costerfield Operation — 2024 Technical Report
| Company | Mandalay Resources |
| Date | 2024 |
| Region | Victoria, Australia |
| Commodities | Gold, Antimony |
Executive Summary
The Brunswick Processing Plant at the Costerfield Operation treats antimony and gold rich sulfide ore through a conventional comminution and flotation style concentrator. Operating since 2007 and managed by Mandalay Resources since late 2009, the plant has undergone several upgrades to increase production capacity to approximately 10,000–13,000 t/month. The facility operates 24 hours per day, 7 days a week, utilizing a well-proven circuit suited to processing the remaining Costerfield ores in the Life of Mine plan.
The processing circuit includes surface crushing and screening, followed by a two-stage closed circuit ball milling circuit. Gravity concentration is employed using centrifugal style concentrators and shaking tables to recover a gold-rich concentrate. The remaining ore undergoes flotation using StackCell roughers, tank cells, and CavTube columns to recover an antimony-gold rich sulfide concentrate.
Recent upgrades include the installation of CavTube flotation columns in April 2021 and additional mobile impact crushers in 2022 to improve throughput and redundancy. The plant demonstrates consistent recoveries, with forecast average LoM 2024 recoveries of 90% for antimony and 93.6% for gold. Tailings are managed via TSFs and underground pastefilling.
Website: https://alkres.com/projects/costerfield/ Report Date: 2024 Region: Victoria, Australia Project Status: Commodity: Gold, Antimony Throughput: Mine Life: Mine Type: Ore type:Costerfield Property — 2021 Technical Report
Costerfield Property — 2021 Technical Report
| Company | Mandalay Resources |
| Date | 2021 |
| Region | Victoria, Australia |
| Commodities | Gold, Antimony |
| Mine Type | Underground |
| Throughput | 13,000 dmt/month |
| Status | Operating |
Executive Summary
The Brunswick Processing Plant at the Costerfield Property treats antimony and gold rich sulphide ore through a conventional comminution and flotation style concentrator. The plant has been operating since 2007 and has been managed by Mandalay Resources since late 2009. Recent upgrades have increased production capacity to approximately 13,000 dry metric tonnes per month over the 2015 to 2021 calendar years. The concentrator operates 24 hours per day, 7 days per week, with crushing operations adhering to noise restriction guidelines during extended dayshift hours.
The processing circuit includes a two-stage closed circuit ball milling circuit fed by underground ore. Centrifugal style gravity concentrators recover a gold-rich gravity concentrate which is upgraded on shaking tables and sold as a separate product. The secondary milled products are processed through a flotation circuit comprising StackCell roughers, tank cells, and CavTube flotation columns added in April 2021. The flotation concentrate is dewatered through thickeners and filtration to produce a final antimony-gold concentrate product shipped overseas.
Forecast recoveries for the Life of Mine plan are 94.1% for antimony and 92.7% for gold, consistent with 2021 end-of-year reconciled plant recoveries. Further incremental plant upgrades scheduled for 2022 include a second filter press for redundancy and a third impact crusher to transition crushing to a two-stage operation. The flowsheet is well-proven and suited to processing the remaining Costerfield ores in the Life of Mine plan.
Website: https://www.mining-plus.com/case-study/costerfield/ Report Date: 2021 Region: Victoria, Australia Project Status: Operating Commodity: Gold, Antimony Throughput: 13,000 dmt/month Mine Life: Mine Type: Underground Ore type:Costerfield Operations — 2020 Technical Report
Costerfield Operations — 2020 Technical Report
| Company | Mandalay Resources |
| Date | 2020 |
| Region | Victoria, Australia |
| Commodities | Gold, Antimony |
Executive Summary
The Brunswick Processing Plant at the Costerfield Operations is an underground mine facility that has been operating since 2007 and has been managed by Mandalay Resources since late 2009. The plant processes sulphide gold-antimony ore through a conventional comminution and flotation-style concentrator. Since 2009, various upgrades have increased production to an average of approximately 12,000 tonnes per month over the 2015–2019 period, with a budgeted throughput of 12,940 t/month for 2020. The plant operates continuously, 24 hours per day, 7 days per week.
The processing circuit includes a two-stage closed-circuit ball milling system fed by a mobile impact crusher. Gravity concentration is employed using centrifugal-style concentrators and shaking tables to recover a high-grade gold concentrate, which accounts for 20%–40% of the gold in the feed. The remaining gold and antimony are recovered through a flotation circuit comprising rougher, scavenger, and cleaner stages using Denver cells and a trial StackCell® unit. The final concentrate is dewatered via thickening and filtration before shipment.
Recovery rates for 2019 were 95.3% for antimony and 77.7% for gold, with forecasts for the Life of Mine (LoM) to end-2020 estimating 96.0% antimony and 87.0% gold recovery. The plant capacity has been successfully upgraded to over 14,000 t/month, though recent production has been constrained by underground mining rates. Ongoing projects focus on mitigating gold recovery issues associated with arsenopyrite in the Brunswick ore and increasing dewatering capacity.
Processing Overview
- Crushing: Mobile Impact Crusher (Finlay I-130RS)
- Milling: Two Ball Mills in Series
- Gravity: Centrifugal-style Gravity Concentrators, Shaking Table
- Flotation: Rougher, Scavenger, Cleaner (Denver DR100, DR15, StackCell)
- Leaching: None
- Dewatering: Thickening, Plate and Frame Pressure Filter
Reports
Costerfield Property — 2020 Technical Report
Costerfield Property — 2020 Technical Report
| Company | Mandalay Resources |
| Date | 2020 |
| Region | New South Wales, Australia |
| Commodities | Antimony, Gold |
Executive Summary
The Brunswick Processing Plant at the Costerfield Property treats antimony and gold rich sulphide ore through a conventional comminution and flotation style concentrator. Operating since 2007 and managed by Mandalay Resources since late 2009, the plant has undergone several upgrades to increase production capacity to approximately 12,000 t/month over the 2015 to 2020 calendar years. The concentrator operates 24 hours per day, 7 days per week, with crushing operations adhering to noise restriction guidelines during extended dayshift hours.
The processing circuit includes surface crushing and screening, a two-stage closed circuit ball milling circuit, and centrifugal style gravity concentrators to recover a gold-rich gravity concentrate. The secondary milled products are processed through a flotation circuit comprised of StackCell® roughers, tank cells, scavenger, and cleaning stages. The final antimony-gold concentrate is dewatered and shipped overseas, while tailings are thickened and pumped to storage facilities.
Plant upgrades scheduled for 2021 include a second Stack Cell® primary rougher and additional flotation cells on the final tailings to recover a separate, lower grade antimony-gold concentrate. The plant has demonstrated ongoing production creep, with average throughput between 2015 and 2020 ranging from approximately 11,900 to 12,979 DMT/month. Forecast recoveries for the Life of Mine (LOM) are 95% for antimony and 90% for gold.
Website: https://www.mining-plus.com/case-study/costerfield/ Report Date: 2020 Region: New South Wales, Australia Project Status: Commodity: Antimony, Gold Throughput: Mine Life: Mine Type: Ore type:Brunswick Processing Plant at Costerfield: Gold and Antimony Recovery
The Brunswick processing plant is the concentrator for Alkane Resources’ Costerfield gold-antimony operation in central Victoria, Australia. It is not a separate Brunswick mine. The plant receives high-grade underground ore from deposits in the Costerfield district and uses crushing, two-stage ball milling, gravity concentration and sulphide flotation to produce separate gold and antimony-gold concentrate products. This profile consolidates MillMatters’ duplicated Brunswick plant pages and distinguishes the historical 2021–22 operating data from current owner information.
| Owner | Alkane Resources, 100%, following its August 2025 merger with Mandalay Resources |
|---|---|
| Operation | Costerfield gold-antimony operation |
| Location | Central Victoria, Australia; approximately 50 km east of Bendigo |
| Feed sources | Underground deposits in the Costerfield district, including Augusta, Cuffley, Brunswick, Youle and Shepherd |
| Commodities | Gold and antimony |
| Plant route | Crushing and screening, two-stage ball milling, gravity gold recovery, antimony-gold sulphide flotation, concentrate filtration and tailings storage |
| Current owner-stated plant capacity | 140,000 t/a |
| Profile last reviewed | August 30, 2026 |
Brunswick processing flowsheet
Costerfield ore is narrow-vein, high-grade material containing gold and antimony-bearing sulphides. The plant first removes liberated gravity gold, then floats the remaining antimony-gold sulphide minerals into a saleable concentrate. This split route is important: the gravity product is sold directly to a refinery, whereas the flotation product is thickened, filtered and shipped as concentrate.
1. Crushing, screening and fine-ore storage
Historical plant descriptions identify two diesel-powered Finlay I-130RS mobile impact crushers in duty-and-standby service, operating in closed circuit with a 12 mm vibrating screen. Crushed material is stored in two fine-ore bins of approximately 120 t each before milling. Earlier planning described a third Finlay I-140RS crusher to create a two-stage crushing configuration; this is retained here as historical upgrade context rather than assumed current equipment status.
2. Two-stage ball milling and gravity recovery
Two ball mills operate in series with classification. The primary mill uses a Dutch State Mines screen: screen oversize returns for additional grinding and the undersize feeds centrifugal gravity concentration. Historical reports identify gravity recovery of approximately 40–55% of gold from Youle ore, followed by upgrading on a shaking table. The secondary mill operates with cyclones and produces flotation feed near a P80 of 60 µm.
3. Antimony-gold flotation
Cyclone overflow is conditioned with lead nitrate and potassium amyl xanthate (PAX) before rougher and scavenger flotation. The circuit includes two 48-inch StackCell roughers, two rougher tank cells, Denver DR100 rougher/scavenger cells and DR15 cleaner cells. Two Eriez CavTube columns commissioned in 2021 treat a lower-grade stream or scavenger tailings to recover additional antimony-gold sulphide concentrate.
4. Concentrate handling
Flotation products are thickened and dewatered in a plate-and-frame pressure filter. Filter cake is bagged for export, while filtrate returns to the process-water circuit. Gold-rich gravity concentrate is handled separately and sold directly to a refinery.
Principal equipment and historical operating data
| Area | Equipment or parameter | Reported value or configuration |
|---|---|---|
| Current plant capacity | Alkane operation profile | 140,000 t/a |
| Historical plant rate | 2021–22 report basis | Approximately 12,500–13,000 dry t/month; peaks near 14,000 dry t/month |
| Crushing | Mobile impact crushers and screen | Two Finlay I-130RS units, duty and standby; 12 mm screen |
| Fine-ore storage | Bins | Two × approximately 120 t |
| Primary milling | Ball mill with DSM screening | Gravity recovery from screen undersize |
| Secondary milling | Ball mill and cyclones | Flotation feed target P80 approximately 60 µm |
| Gravity | Centrifugal concentrator and shaking table | Historical Youle recovery approximately 40–55% of gold to gravity |
| Flotation | StackCell, conventional cells and CavTube columns | Antimony-gold sulphide recovery and cleaning |
| Water treatment | Reverse-osmosis plant | Historical description cites approximately 2 ML/d capacity |
The historical monthly-rate and recovery values are not current plant guidance. They are retained to explain the original circuit and its ore-specific performance.
Gold and antimony products
The circuit produces two distinct saleable streams. Free or readily liberated gold recovered by the gravity circuit is upgraded on a shaking table and sold as high-grade gold concentrate. The flotation circuit produces an antimony-gold sulphide concentrate that is dewatered, bagged and marketed to third parties. This process arrangement is why Costerfield can recover both a precious metal and a critical mineral from the same narrow-vein ore system.
Tailings and water management
Thickened flotation tailings are pumped to the Brunswick and Bombay tailings-storage facilities. Process-water recovery comes from thickener overflow and tailings decant, while underground dewatering provides a significant additional water source. Historical operating material also describes reverse-osmosis treatment and evaporation management for surplus or affected water. These systems remain integral to sustaining the small, high-grade plant rather than being separate ancillary facilities.
How to read the capacity and recovery figures
The former duplicate pages mixed several reporting periods. Their 12,500–13,000 dry-t/month and 2021 recovery values describe a historical operating basis; the reported 2022 crusher and filter upgrades were plans, not evidence that all equipment had been installed. Alkane’s current Costerfield profile, published after its merger with Mandalay, identifies the operating Brunswick plant at 140,000 t/a. The two capacity figures should therefore be treated as different reporting bases rather than simultaneous guarantees.
Similarly, Costerfield production and guidance belong to the overall mine operation, not necessarily to one plant campaign. Alkane reports 2024 production of 43,300 oz gold and 1,300 t antimony from Costerfield, with FY2026 guidance of 40,000–45,000 oz gold and 800–900 t antimony. Ore sequencing, grade and the mix of Youle and Shepherd feed can change these outcomes without altering the basic gravity-plus-flotation route.
Technical-report library and sources
| Source period | How it is used in this profile |
|---|---|
| Historical 2021–22 plant descriptions | Crushing, milling, gravity, flotation, filtration, water-treatment configuration and ore-specific recovery context |
| Mandalay 2024/2025 technical-report materials | Costerfield reserves, operating context and plant-capital program before the merger |
| Alkane Resources 2025 annual report and current Costerfield profile | Current ownership, 140,000 t/a plant capacity, district feed sources and current production/guidance context |
Additional resources and industry links
Brunswick Processing Plant: Antimony-Gold Sulfide Ore Concentration
Overview
The Brunswick Processing Plant in Victoria, Australia is a conventional comminution and flotation concentrator that has been processing antimony and gold-rich sulfide ores since 2007. Acquired by Mandalay Resources in late 2009, the plant has undergone several upgrades to achieve current throughput capacities of 10,000-13,000 tonnes/month. The facility operates 24/7 with crushing operations following noise restriction guidelines during extended day shifts.
Key Process Stages
- Crushing & Screening: Two-stage closed circuit using Finlay mobile impact crushers (I-130RS, I-140RS) and cone crusher (C-1540RS) with 35mm and 12mm screens
- Milling: Two ball mills in series with DSM screen and hydrocyclone classification (target P80 of 53µm)
- Gravity Recovery: Centrifugal concentrators recover gold-rich concentrate (55-70% Au recovery) upgraded via shaking table
- Flotation: StackCells (48″) and Denver DR cells (100 & 15) with CavTube columns added in 2021 for tailings reprocessing
- Concentrate Handling: Dual thickener system feeding plate-and-frame filter press for final dewatering
- Tailings Management: Thickened tailings directed to TSFs or underground paste fill operations
Critical Data
| Parameter | Value |
|---|---|
| Throughput Capacity | 10,000-14,000 dmt/month |
| Current Average Throughput | 11,000-13,000 dmt/month |
| LoM Antimony Recovery | 90.1% |
| LoM Gold Recovery | 92.2% |
| Gravity Gold Recovery | 55-70% |
| Target Grind Size | P80 53µm |
| Water Consumption | 1.5-2 ML/day (from mine dewatering) |
Recent Upgrades
- 2021: Installation of rougher/cleaner CavTube flotation columns
- 2024: Addition of Finlay C-1540RS mobile cone crusher
- Ongoing: Construction of new TSF (788,000 dmt capacity) for 2025 commissioning
- Paste fill system expansion with new pug mill installation
Circuit Features
The flowsheet combines proven technologies with strategic upgrades: primary crushing with mobile units, efficient gravity gold recovery ahead of flotation, and modern StackCell/CavTube units complementing traditional Denver cells. The dual thickener system allows separate processing of main and low-grade concentrates. Water management includes reverse osmosis treatment and extensive recycling from thickener overflows.
Brunswick Processing Plant: Gravity and Flotation Recovery for Gold-Antimony Ore
The Brunswick Processing Plant at the Costerfield Operation in Victoria, Australia, treats antimony and gold rich sulfide ore through conventional comminution, gravity, and flotation methods. The operation is wholly owned by Alkane Resources Limited and has been operating since 2007.
Critical Data
| Parameter | Value | Unit | Notes |
|---|---|---|---|
| Target commodity | Gold, antimony | Not applicable | Antimony-gold rich sulfide ore |
| Plant status | Operating | Not applicable | Since 2007 |
| Throughput capacity | 14,000 | dmt/month | Design value; typically averages 11,000–13,000 dmt/month |
| Average throughput (2024–2026) | 11,600 | dmt/month | Range: 10,500–12,500 dmt/month |
| Target grind size | 53 | µm | P80 |
| Gravity gold recovery (Youle and Shepherd blend) | 55–65 | % | Test result; can exceed 70% |
| Crushing screen size (primary) | 35 | mm | Closed circuit |
| Cone crusher screen size | 12 | mm | Closed circuit |
| Concentrate bag weight | 900–1,600 | kg | Per bag |
| TSF design capacity | 788,000 | dmt | New TSF operational July 2025 |
| Average tails thickener underflow solids density | 50 | % w/w | +/- 10% |
| RO plant treatment capacity | 2 | ML/day | Design value |
| Splitters Creek evaporation capacity | 104 | ML/year | Net (evaporation minus rainfall) |
| Power supply provision | 2 | kVA | Additional capacity for mill |
Overview
The Brunswick Processing Plant sits within the Costerfield mining district roughly 10 km northeast of Heathcote, Victoria. The plant uses a flowsheet that has operated for more than 18 years. Underground feed moves through surface crushing and screening, then a two-stage closed circuit ball milling circuit. Centrifugal gravity concentrators recover gold from the combined primary mill product and secondary mill discharge. The gravity concentrate upgrades further over shaking tables and sells as a separate product shipped to a local refinery.
Secondary milled products go through size classification and then a flotation circuit built around two StackCell roughers, two additional rougher tank cells, and the original flotation train with rougher, scavenger, and single stage cleaning. Two CavTube flotation columns were added at the tailings end and commissioned in April 2021. Flotation concentrate dewaters through thickeners and a pressure filter to produce the final antimony-gold concentrate. That product is bagged in 900 kg to 1,600 kg bags, trucked to port, packed into shipping containers, and sent overseas for refining.
Flotation tailings thicken before pumping to a new tailings storage facility. Underground paste fill is on hold until more voids become available.
Key Process Stages
The crushing and screening circuit uses a primary and secondary crushing plant. The primary circuit runs in closed circuit with a 35 mm vibrating screen. It uses a duty and a standby diesel-powered Finlay I-130RS mobile impact crusher and a Finlay I-140RS mobile impact crusher. The primary product feeds a Finlay C-1540RS mobile cone crusher operating in closed circuit with a 12 mm screen. Crushed ore loads into a 40 t fine ore bin or directly onto a 1,500 t capacity reclaim feeder. The crushing and milling circuit has a demonstrated average throughput capacity of 10,000 to 13,000 dmt per month.
Crushed ore discharges onto the primary mill feed conveyor. The milling circuit comprises two ball mills in series, both in closed circuit. The primary mill works in closed circuit with a Dutch State Mines screen. Screen oversize returns to the primary mill. Screen undersize feeds a centrifugal gravity concentrator. That unit recovers a small mass of high-grade gold concentrate sent to the gold room for further upgrading using shaking tables and a small centrifugal-style gravity concentrator. The final gravity concentrate goes directly to a gold refinery within the state. Gravity gold recovery from the Youle and Shepherd blend feed typically runs 55 to 65% but can exceed 70% of the gold in the feed. Gravity tailings pump to a dedicated classifying hydrocyclone. The overflow goes to the flotation plant feed or to the concentrate thickener. The underflow returns to the secondary ball mill. The target grind size is 53 µm P80. The secondary ball mill discharge combines with the DSM screen undersize and also feeds the centrifugal gravity concentrator.
The flotation circuit is designed to recover an antimony-gold rich sulfide concentrate. Feed comes from the secondary ball mill cyclone overflow. That overflow goes to a conditioning tank where lead nitrate and potassium amyl xanthate are added. The conditioning tank feeds two 48-inch flotation StackCells currently operating in series with two site-fabricated rougher tank style flotation cells also in series. The StackCell and rougher tank cell concentrates combine with the final cleaner concentrate as the final product.
Rougher tank cell tailings flow to the original flotation circuit. That circuit consists of eight square Denver DR100 cells for the remaining rougher and scavenging duties, followed by six Denver DR15 cells for cleaning duties. Concentrate from the Denver rougher cells pumps to the cleaner cells. The tailings from those cells become feed for the scavenger cells. Scavenger concentrate recycles to the Denver rougher feed. Scavenger tailings pump as feed to the rougher CavTube column flotation cell. The rougher CavTube column tail is the final tail stream and reports to the final tailings thickener. Rougher CavTube concentrate feeds the cleaner CavTube column. Cleaner CavTube tails recycle to the rougher CavTube feed. Cleaner CavTube concentrate goes back to the Denver rougher cells. Denver cell cleaner tailings also recycle to the rougher cells. During low antimony feed grade periods, a StackCell is used as a secondary cleaner.
Final concentrate from the combined StackCells, tank rougher cells, and cleaner flotation stages pumps to concentrate thickener 1. Overflow from that thickener goes to concentrate thickener 2 for clarifying. The thickened underflow from both thickeners pumps directly to a plate and frame pressure filter for final dewatering. The filter cake discharges directly into concentrate bags. Filtrate recycles to the concentrate thickener. Concentrate thickener 2 overflow recycles back to the plant as process water.
Flotation tailings settle in a thickener. The tailings thickener overflow recycles to the plant as process water. Thickened solids pump to the TSF and discharge via a conventional spigot system. Any additional water from the tailings decants and recycles to the plant.
Additional Interesting Data and Summary
The plant operates 24 hours per day, 7 days per week. Crushing runs under noise restriction guidelines during extended dayshift hours. Throughput capacity reaches up to 14,000 dmt per month but typically averages closer to 11,000 to 13,000 dmt per month. Since operations began, the plant has shown ongoing production creep from around 5,000 t per month in January 2012. Annual plant throughput has matched mining rates in recent years as underground mine production has at times limited available mill feed. Average throughput from 2024 to 2026 ranges from 10,500 dmt to 12,500 dmt per month, averaging 11,600 dmt per month.
About 10,200 dmt of feed sits on the ROM pad and central stockpile. Total stocks in pit stockpiles, overflow stockpiles, ROM, and COS total roughly 49,000 dmt. The operation maintains mill feed stocks to provide a buffer for any mining disruption.
Head grade versus recovery relationships have been developed for both antimony and gold using plant operating data. The gold head grade versus tailings grade relationship for non-Brunswick ores used January 2022 to February 2026 monthly production data. Youle and Shepherd ore blends processed recently determined recovery for non-Brunswick ores. Youle and Kendal, a sub-domain of Youle, will continue to form the bulk of mill feed from non-Brunswick lodes. The antimony recovery algorithm for non-Brunswick ores used the same monthly operational data to show lower head grades associated with higher proportions of Shepherd ore.
Forecast antimony and gold recoveries for life-of-mine planning, budgeting, and economic modelling are based on these recovery relationships. The algorithms update annually to show changes in ore blend or plant upgrades. The recovery relationships are supported by historical concentrator recoveries at similar feed grades and compare well to previous grade and recovery relationships.
Water services consist of raw water, process water, and excess water disposal systems. Process water comes from concentrate thickener overflow, tailings thickener overflow, and TSF decant return water. The plant operates with a positive water balance. Excess water goes through a permeate reverse osmosis plant designed to treat 2 ML per day, constructed in 2014. A pre-treatment plant for the RO plant was installed in 2017. The Splitters Creek evaporation facility treats about 104 ML per year net and handles the bulk of excess water.
The plant requires both low pressure and high pressure air supplies. Three separate LP blowers supply the rougher, scavenger, and cleaner cells. Existing tank cells run off HP air. The HP air supply was upgraded to a variable speed compressor in 2017. The pressure filter also runs using HP air.
Power supply and reticulation circuits were upgraded in 2019, consolidating three separate incoming electrical supplies into a single source. This allowed greater efficiencies and local site back-up generation from a single point. Provision for additional power demand for the mill up to 2 kVA exists.
No major fixed plant upgrades have occurred since 2021 when the second StackCell and rougher and cleaner CavTube columns were installed. A third mobile impact crusher was purchased in 2022. A mobile cone crusher was purchased in 2024. In mid-2024, a stacker conveyor was delivered to deliver crushed fines to a central stockpile. A jaw crusher pre-crushing trial on the lower ROM pad aimed to increase wear life and crushing capacity. A rolls crusher, TCF 400, has been purchased to crush ball mill scats. The milling circuit remains fundamentally unchanged with small modifications including a second conveyor belt from the tunnel feeder. The finer crushed ore feed size allows the target throughput rate on all ore types.
No recent changes to the flotation circuit have been made other than pipework modifications. One modification allows using a StackCell as a second cleaner during low antimony head grade campaigns. Two concentrate thickeners now operate in series rather than parallel. Both thickeners feed the pressure plate and frame filter press in parallel. The filter press loading and pressing time is not a production bottleneck. Settling capacity in the concentrate thickener can be a bottleneck at higher metal production rates.
The tailings thickener has sufficient capacity for current throughput. Both Bombay and Brunswick TSFs are at capacity and no longer in use. A 5-year operating TSF with a design capacity of about 788,000 dmt, situated northwest of the Brunswick Pit, began construction in September 2024 and became operational in July 2025. Paste filling used cement binder mixed with thickened plant tailings pumped underground. A pug mill purchased and installed at the Augusta Mine site in 2024 can process the entirety of thickened mill tailings continuously. Paste filling was the primary tailings disposal method until the new TSF was completed but is not currently operational. It will resume once more underground disposal locations are identified.
All reagents arrive on site pre-mixed as liquids. The reagent storage area is being upgraded so one operational intermediate bulk container serves as the primary feed for each reagent, with top up by gravity from a second IBC above. Reagent pumps will be upgraded from EWIN 8×6 Iwaki to DS500 pumps. The DS500 hose pumps are considered more reliable, provide more accurate dosing, and require less maintenance. The plan is to integrate them into the SCADA system. The pre multimedia filters and internal media on the RO plant were replaced in 2025.
Key Processes
- Conventional comminution through primary and secondary crushing with impact and cone crushers, followed by two-stage closed circuit ball milling
- Gravity gold recovery using centrifugal concentrators on combined mill products, with upgrading on shaking tables to produce a separate gold concentrate for local refining
- Flotation recovery of antimony-gold sulfide concentrate using StackCell roughers, tank cells, Denver DR cells, and CavTube column flotation cells
- Concentrate dewatering through series thickeners and a plate and frame pressure filter, with bagging for containerized shipment overseas
- Tailings thickening and disposal to a new TSF, with paste fill capability on hold pending available underground voids
Source: Costerfield Operation, Victoria, Australia, NI 43-101 Technical Report, 11 September 2026. Project website: Costerfield Operation
Brunswick Processing Plant – 2014 Technical Report
Brunswick Processing Plant – 2014 Technical Report
Company: Not specified in text Mine/Project: Brunswick Processing Plant Region: Not specified in text Year: 2014 Commodities: Gold, Antimony
Executive Summary
This report details the operational status and planned upgrades for the Brunswick Processing Plant, which processes a sulphide gold-antimony ore. The plant operates continuously, with crushing limited to specific hours to minimize noise impact. A recent upgrade involving a portable crushing unit has successfully increased the plant’s throughput capacity to 10,000 t/mth.
The processing circuit includes a multi-stage crushing and screening system, followed by a ball mill circuit with classification and gravity concentration. The flotation circuit produces an antimony/gold concentrate, while gravity concentrates can be further refined or blended. Current recovery rates are approximately 95% for antimony and 90% for gold. The report also outlines planned upgrades for 2014, focusing on improving the reliability and efficiency of the flotation section, cleaner capacity, and concentrate slurry storage.
Further details are provided on the crushing, milling, flotation, thickening, filtration, and tailings circuits, along with information on reagent management, services (water, air, power), and recovery performance. The planned upgrades aim to maintain current recovery levels and enhance overall plant reliability and efficiency in handling increased throughput.
Website: https://www.brunswickbierworks.com/ Report Date: Region: Project Status: Commodity: Throughput: Mine Life: Mine Type: Ore type:Brunswick Processing Plant: Antimony-Gold Sulphide Ore Concentration
Overview
The Brunswick Processing Plant is a conventional comminution and flotation concentrator that has been processing antimony and gold-rich sulphide ores since 2007. Acquired by Mandalay Resources in late 2009, the plant has undergone several upgrades to increase its capacity to approximately 13,000 tonnes/month. The facility operates continuously (24/7) with crushing operations following noise restriction guidelines during extended day shifts.
Key Process Stages
- Crushing & Screening: Two-stage closed circuit using Finlay I-130RS mobile impact crushers (12mm product size)
- Milling: Two ball mills in series with DSM screen and centrifugal gravity concentrators (target P80 of 60µm)
- Gravity Concentration: Recovers 40-55% of gold using centrifugal concentrators and shaking tables
- Flotation: StackCell® roughers, tank cells, Denver DR cells, and CavTube® columns (added April 2021) with lead nitrate and PAX reagents
- Concentrate Handling: Dual thickener system with plate-and-frame pressure filtration
- Tailings: Thickened to 50% w/w solids and pumped to one of two TSFs
Critical Data
| Parameter | Value |
|---|---|
| Throughput Capacity | 13,000-14,000 dmt/month |
| Antimony Recovery | 94.1% (2022 forecast) |
| Gold Recovery | 92.7% (2022 forecast) |
| Gravity Gold Recovery | 40-55% of feed gold |
| Operating Schedule | 24/7 (crushing limited to day shift) |
| Water Usage | 1.5-2 ML/day from mine dewatering |
Recent Upgrades
- Second StackCell® flotation unit installed (July 2021)
- CavTube® column flotation cells commissioned (April 2021)
- Additional 2.4m³ concentrate thickener installed (2019)
- Finlay I-140RS impact crusher planned (2022)
- Second filter press planned (2022)
Water Management
The plant operates with a positive water balance using a 2 ML/day reverse osmosis plant and Splitters Creek evaporation facility (104 ML/year capacity). Process water is recycled from thickener overflows and TSF decant systems.
