This PEA describes a proposed 4,000 tpd flotation mill and sulphuric acid cracking plant for the Ashram rare earth project, with no historical milling background.
Report context
The report, dated as part of the Preliminary Economic Assessment for Commerce Resources Corp. – Ashram Project, was prepared by SGS Geostat. Since Ashram is a new project, there is no historical milling background. The assessment presents a proposed mill design and processing route based on testwork and assumptions, with operating cost estimates considered to have an accuracy range of +/-30%.
Processing route
Historical background
Since Ashram is a new project, there is no historical milling background.
Proposed mill design and assumptions
A 4,000 tpd mill is proposed in this study. The mill process will be conventional with operation relying on operators’ experience and skill supported by electronic monitoring and instrumentation. Mill design criteria follow those used in several mines in Canada where, apart from the run of mine grizzly, hopper, jaw crusher and water tanks, the entire mill services and operations are under the same roof.
The preliminary assessment is based on assumptions including: a good mill design will have a good overall TREO grade and recovery; Commerce will buy new milling equipment unless in extremely good working condition; the mine will be able to feed the mill at a rate of 4,000 tpd, 7 days per week; no major setbacks will be encountered with environmental agencies, trade unions and/or indigenous people; 3-phase diesel power generators delivering about 10MW will be available on site; approximately 5 hectares of a more or less flat site will have to be prepared for the mill and its ancillary infrastructure; it will be possible to dispose of tailings without jeopardizing the surrounding environment; the mineral concentrate grade will be a minimum of 10% TREO with recovery in the 70% range; the ore liberation size is typically less than 30 µm, down to <5 µm; and no provision was made for the recovery of other minerals (fluorite, apatite).
Crushing
Run of mine ore is delivered from the mine by haul trucks. Whenever possible the ore will be dumped directly in the jaw crusher feed hopper. Because mining and crushing operations will not always be on the same time schedule, it is assumed that 25% of the time the haul trucks will proceed to the run of mine stockpile and the rest of the time they will dump directly onto the grizzly above the crusher feed hopper. The run of mine stockpile area is sized to hold approximately 30,000 tonnes of ore. Secondary handling will be by a Caterpillar 938 front end loader.
A grizzly having 15” x 20” openings scalps the oversize rock. Oversize will be broken in place with a pneumatic rock breaker. Grizzly undersize falls into a 100 tonne capacity hopper which feeds a 17’ x 5’ apron feeder discharging on an incline fix bar scalper. Bar scalper oversize falls by gravity into a 48” x 60” jaw crusher while undersize, crushed ore and fines from the apron feeder report to a 60” wide sacrificial belt conveyor, then to a 36” wide belt conveyor which discharges on a buffer stockpile. The stockpile, which is above ground, has a live load of 4,000 tonnes and feeds through longitudinal slots two apron feeders located in an 8’ x 8’ underground concrete tunnel.
Grinding and classification
Apron feeders discharging on a second 36” belt conveyor feed a 10’ x 20’, 1200 kW SAG mill. The SAG mill discharges on a set of three 60” x 120”, 16 mesh Derrick screens. Derrick screen oversize is conveyed back to the SAG mill feed via three 24” belt conveyors in series while undersize is pumped to a set of two 20” cyclones. Cyclones underflow flow by gravity to a 4-way splitter box feeding four 13.5’ x 13’, 900 kW ball mills in parallel. Cyclone overflow reports to the first conditioner of the flotation circuit. The SAG and ball mills are sized for an ore having an average Work Index of 14.0 kW-h/t.
Flotation
The larger conditioner, with dimensions 3 m diameter x 4 m height, overflows to a second 2.5 m diameter x 3 m height conditioner that reports to a bank of Denver DR type 300 x 4 cells rougher. Rougher tailings are pumped to a third 2 m diameter x 2 m height conditioner, overflowing in a primary Denver DR type 100 x 6 cells scavenger. Tailings from the primary scavenger are pumped to a fourth 2 m diameter x 2 m height conditioner which overflows into a second Denver DR type 100 x 6 cells scavenger. Tailings from the second scavenger are pumped to a fifth 2 m diameter x 2 m height conditioner overflowing into a third Denver DR type 100 x 6 cells. Tailings from this bank of cells are the final tailings, which after sampling are pumped to the tailings pond.
Rougher concentrate is pumped to a bank of Denver DR type 24 x 4 cells primary cleaner. Concentrate from this cleaner is the final concentrate and is pumped to the mill thickener. Conditioner and flotation cells are roughly sized from Hazen’s metallurgical tests.
Thickening and filtration
Concentrate from the primary cleaner is pumped to a high capacity thickener. Thickener underflow is pumped via a diaphragm pump to a stock tank having a 2-hour retention time. From the stock tank, the thickener underflow concentrate is pumped via a second diaphragm pump to a Larox type pressure filter. From the pressure filter the concentrate at approximately 8% moisture is conveyed to the concentrate shed or to the acid cracking plant. No tests were done to size the filter and the thickener.
Thermal cracking
Since thermal cracking of the mill concentrate to produce high grade TREO product is ongoing, it is not possible to give an exact description of the process. For the economic evaluation of the PEA, a sulphuric acid cracking technique, resulting in the production of a rare earth carbonate (REC) product, is selected.
The major components of the acid cracking section include roasting, leaching, calcium and fluorine removal, thorium and iron precipitation and removal, REE carbonate precipitation, centrifuging and drying of the REE carbonate. The chemical upgrading begins with the mill flotation concentrate being soaked in concentrated sulphuric acid (98% pure). The acidified concentrate is roasted at a temperature of ±250°C in a rotary kiln to decompose the rare earth minerals (monazite, bastnäsite, and xenotime) as well as the gangue. The roasted concentrate is water leached, thickened and filtered. Rare earths and other elements are in solution, with calcium being removed as gypsum (CaSO₄) to the residue. Hydrogen fluoride (HF) created is scrubbed and disposed of. The solid residue (gypsum) is disposed to the mill tailings pond while the rare earth element enriched solution undergoes clarification. Leached radioactive elements (thorium only as uranium is not present) and other impurities are selectively removed via pH control and neutralization with caustic soda, precipitated, and allowed to report to the mill tailings. When impurities are removed, the REE enriched solution is precipitated with sodium carbonate into an REE carbonate form, then filtered, dried and bagged ready for dispatch. For the purposes of the PEA, the cracking process will end at the production of a REC product.
Key reported parameters
| Parameter | Value | Basis |
|---|---|---|
| Proposed mill throughput | 4,000 tpd | Proposed design |
| Annual mill feed | 1,400,000 tonnes | Proposed design |
| Mineral concentrate production | 178,000 tonnes per year | Proposed design |
| Anticipated concentrate grade | Minimum 10% TREO | Proposed design/assumption |
| Anticipated mill recovery | 70% range | Proposed design/assumption |
| Ore liberation size | Typically less than 30 µm, down to <5 µm | Testwork basis |
| Mill power demand | Approximately 7,000 kW | Design estimate |
| Mill power consumption | 41.9 kW-h/t | Design calculation |
| SAG mill | 10’ x 20’, 1200 kW | Proposed design |
| Ball mills (four in parallel) | 13.5’ x 13’, 900 kW each | Proposed design |
| Average Work Index | 14.0 kW-h/t | Basis for mill sizing |
| Mill operating cost | $23.87 per tonne milled | Estimate (+/-30% accuracy) |
| Mill capital cost estimate | $160.0 million | Estimate (remote area factor) |
| Mill construction cost per tonne per day | Approximately $40,000 | Estimate (remote area factor) |
| Anticipated cracking plant recovery | 95% of REE | Testwork basis |
| Cracking plant feed grade | 10.0% TREO | Demonstrated by Hazen |
| Cracking plant OPEX | $17.40 per tonne of RoM | Estimate from similar deposits |
| Cracking plant annual OPEX | $24,360,000 | Estimate |
| Cracking plant CAPEX | $35,000,000 | Estimate |
| Final product weight | Approximately 20% of concentrate feed weight (36,000 tonnes pure REC) | Testwork basis |
| Sulphuric acid consumption | 178,000 tpa (approximately 1 tonne acid per 1 tonne flotation concentrate) | Base case scenario |
Project website: https://montroyalres.com/
Technical qualifications
The mill operating costs presented in this section are strictly for the mineral processing for the production of a 10% TREO mineral concentrate. The mill operation costs are considered to have an accuracy range of +/-30%. Conditioner and flotation cells are roughly sized from Hazen’s metallurgical tests. No tests were done to size the filter and the thickener. Because thermal cracking of the mill concentrate to produce high grade TREO product is ongoing, it is not possible to give an exact description of the process. For the cracking plant, OPEX and CAPEX were estimated from available studies realized for ore deposits similar to Ashram.
Source: Commerce Resources Corp. – Ashram Project – Preliminary Economic Assessment, SGS Geostat, Section 17 Recovery Methods.
Consolidated report summaries
The following former standalone pages about this operation were consolidated here in October 2026. They are retained for source traceability; dates and figures reflect each report’s own effective date and may be superseded by the current information above.
Ashram Rare Earths Project: Process Design from Mine to Mixed Rare Earth Carbonate
A two-phase recovery strategy uses flotation concentration at the Quebec mine site followed by acid baking and hydrometallurgical refining in Saguenay to produce a mixed‑rare earth carbonate product.
The Ashram Rare Earths Project is a rare earth element project located in Nunavik, Quebec, Canada. The project is owned by Mont Royal Resources Limited. The preliminary economic assessment (PEA) technical report is effective 29 May 2026. The project is not yet in operation. The development includes a mineral processing facility (concentrator) at the mine site and a separate hydrometallurgical processing facility (Hydromet) located in Saguenay. The concentrator is designed to process run‑of‑mine mineralised material at 1.88% average rare earth oxide (REO) grade.
Critical Data
| Parameter | Value | Unit | Notes |
|---|---|---|---|
| Total processing rate | 1,788,500 | dry tonnes per year | Design value |
| Nominal processing rate | 4,900 | dry tonnes per day | Design value |
| Feed material grade | 1.88 | % REO | Design value |
| Concentrator operating time | 92.0 | % | Design value; crushing circuit is 66.7% |
| Concentrate recovery | 63.2 | % REO | Design value based on flotation testing |
| Concentrate grade | 30.5 | % REO | Design value |
| Concentrator installed power | 14.8 | MW | Design value |
| Concentrator operational power | 12.6 | MW | Design value |
| Hydromet flotation concentrate feed | 69,505 | dry metric tonnes per annum | Design capacity |
| Hydromet MREC product | 33,849 | dry metric tonnes per annum | Design capacity |
| Hydromet operating factor | 90.4 | % | Design value |
| Hydromet electrical power | 1,930 | kW | Estimated value |
| Hydromet natural gas | 43 | GJ/hr | Estimated value |
| Construction timing | Not stated | Not applicable | Not stated |
Overview
The recovery method for the Ashram Project is a two‑stage process. A mineral processing facility at the mine site, located just north of the open pit, crushes, grinds, and floats the ore to produce a rare earth concentrate. That concentrate is then shipped south to a hydrometallurgical plant in Saguenay. The hydrometallurgical plant uses acid baking, water leaching, solvent extraction for thorium removal, oxalate precipitation, and metathesis to produce a mixed‑rare earth carbonate product (MREC). The concentrator is designed to produce an average of 190 tonnes per day of concentrate at around 30% REO, with the grade varying from 28% to 34% with feed grade.
The mineral processing facility’s four main areas are crushing, grinding, flotation, and dewatering. The crushing circuit operates independently from the rest of the concentrator, decoupled by a stockpile. The concentrator operates 24 hours per day, 7 days per week, 52 weeks per year, with an effective operating time of 92%. The crushing circuit has a design operating time of 66.7%.
The hydrometallurgical plant is designed to process 69,505 dry metric tonnes per annum of flotation concentrate and produce 33,849 dry metric tonnes per annum of MREC. The plant operates 330 days per year, 24 hours per day, with an operating factor of 90.4%. The overall hydrometallurgical process recovers rare earth elements at rates ranging from 72.4% for scandium to 90.8% for praseodymium and neodymium, based on the heat and material balance.
Key Process Stages
Mineral Processing Facility (Concentrator)
The crushing area starts with run‑of‑mine material dumped into a ROM feed bin. A static grizzly and fixed rock breaker provide top‑size control. An apron feeder delivers material to a jaw crusher designed to produce a product with P₈₀ of 110 mm. Primary crushed material is conveyed to a covered stockpile.
Two reclaim feeders withdraw crushed material for the grinding circuit. A semi‑autogenous grinding (SAG) mill operates in closed circuit with a trommel screen. The SAG mill is designed to produce a transfer size around 80% passing 1.20 mm. A ball mill in closed circuit with cyclones provides further grinding. Tertiary grinding uses a HIGmill to achieve a P₈₀ of 25 μm. The circuit includes trash screens to remove debris and an inclined plate settler to increase solids density to 50% by weight ahead of flotation.
The flotation circuit uses two conditioning tanks with depressant, pH modifier, and collector before flotation. The circuit consists of rougher, rougher scavenger, three stages of cleaner flotation, and a first‑cleaner scavenger. Flotation feed grade averages 1.88% REO. The flotation circuit tailings grade averages 0.72% REO. The concentrate grade averages 30.5% REO with a recovery of 63.2%. The flotation circuit and dewatering circuits were designed considering the range of anticipated feed grades.
Concentrate dewatering uses a high‑rate thickener with coagulant and flocculant to achieve 65% solids underflow. Two plate‑and‑frame filter presses produce a filter cake. The cake is discharged onto feeders and telescopic conveyors to fill 20‑foot shipping containers, each loaded with around 20 tonnes of concentrate. Containers are stored or loaded directly for shipment south. Tailings from flotation are thickened to 65% solids and pumped to the processed carbonatite storage facility.
Hydrometallurgical Plant (Hydromet)
Area 100 – Pre‑Leach conditions the flotation concentrate by removing acid‑consuming gangue minerals. Barren acidic solution from the oxalate precipitation area is reacted with concentrate in a cascade of three agitated tanks. The reaction completes during thickening. Pre‑leached concentrate is dewatered in a filter press and dried in a rotary dryer to 4% residual moisture. The leach solution goes to effluent treatment.
Area 200 – Acid Bake and Water Leach converts rare earth minerals to water‑leachable sulphate salts. Pre‑leached concentrate is mixed with hot, concentrated sulphuric acid at a 0.56 tonnes acid per tonne solids ratio in a pug mill. The mixture feeds a multi‑zone rotary calciner with 120‑minute residence time and 320°C discharge temperature. The calcined solids are cooled and mixed with water in three agitated tanks to dissolve rare earth sulphates. The slurry is concentrated by decanter centrifuge and filtered on a vacuum belt filter. The residue goes to effluent treatment. The pregnant leach solution is polished in candle filters before thorium recovery.
Area 300 – Thorium Recovery removes thorium from the pregnant leach solution. A battery of six mixer‑settlers uses 30% v/v Cyanex 923 in D80 kerosene at a 1:1 organic‑to‑aqueous ratio. All thorium is extracted along with minor niobium and titanium. The thorium‑free PLS goes to oxalate precipitation. The loaded organic is stripped with oxalic acid in three agitated tanks. A three‑phase separator decants the stripped organic for recycle and sends the aqueous thorium oxalate slurry to effluent treatment.
Area 400 – Oxalate Precipitation selectively recovers rare earths. Thorium‑free PLS reacts with solid oxalic acid and recycled sodium oxalate solution in three agitated tanks. The resulting rare earth oxalates are filtered and washed on two vacuum belt filters. The barren solution returns to the pre‑leach area.
Area 500 – Metathesis converts mixed rare earth oxalates to mixed‑rare earth carbonate product. Rare earth oxalates react with sodium carbonate solution at 90°C in four agitated tanks with hydrocyclones for partial dewatering between stages. The MREC product is filtered on a vacuum belt filter and dried in an indirect rotary dryer to 0.1% residual moisture. The MREC is then packaged and distributed.
Area 600 – Effluent Treatment processes all process effluents. Thorium oxalate residue is thickened and centrifuged to a waste paste. Barren solutions and residues are neutralised to pH 8 with quicklime in three agitated tanks, followed by thickening and filter pressing. The solid is disposed of as tailings.
Area 700 – Plant Scrubbing treats the sulphuric acid recovery vent. The vent gas, containing sulphuric acid vapour, hydrofluoric acid, carbon dioxide, and water vapour, is neutralised with slaked lime in a flue gas desulphurisation scrubber.
Area 800 – Reagents and Utilities stores and distributes major reagents. Sulphuric acid (93 wt%) is delivered by railcar. Oxalic acid is supplied in bulk containers and dissolved on site. Sodium carbonate is delivered by truck or rail and stored in a silo. Quicklime is pneumatically conveyed and slaked on site. Solvent extraction reagents are delivered by truck in isotainers. Fresh water is stored in an insulated tank. Fire water shares the same tank with priority outlets. Potable water is produced from fresh water using softening, chemical dosing, and filtration. Cooling water is generated by evaporative cooling towers at approximately 20°C. Compressed plant air and instrument air are supplied by dedicated compressor systems.
Additional Interesting Data and Summary
The concentrator equipment design factor for crushing equipment is 25%. The design factor for the remaining concentrator is 15%. Major equipment includes a 6.4m diameter SAG mill with 2,000 kW installed power, a 4.6m diameter ball mill with 2,000 kW, and a HIGmill 2300/15000 with 2,300 kW. Rougher flotation uses six 100m³ mechanical cells. The overall rare earth element recovery for the hydrometallurgical plant varies by element, with praseodymium and neodymium achieving 90.8% and cerium achieving 83.1% based on the heat and material balance. The mineral processing facility is designed to achieve 63.2% average REO recovery based on flotation testing. The hydrometallurgical process design criteria is preliminary economic assessment level. The core section has matured to pre‑feasibility level, but additional work is required for full process design criteria to reach that level.
Key Processes
- Crushing: ROM feed through jaw crusher to covered stockpile (P₈₀ 110 mm)
- Grinding: SAG mill, ball mill, and HIGmill tertiary grinding (P₈₀ 25 μm)
- Flotation: Rougher, rougher scavenger, three cleaner stages, and first‑cleaner scavenger
- Flotation reagents: Sulphuric acid (pH modifier), dispersant, depressant, collector, frother
- Concentrate dewatering: Thickener to 65% solids, plate‑and‑frame filter press, container loading
- Tailings dewatering: Thickener to 65% solids, pumped to storage facility
- Hydromet pre‑leach: Acidic leach to remove gangue, dewatering, drying
- Hydromet acid bake: Pug mill with sulphuric acid, rotary calciner at 320°C
- Hydromet water leach: Dissolution of rare earth sulphates, centrifugation, belt filtration
- Thorium removal: Six‑stage solvent extraction with Cyanex 923
- REE oxalate precipitation: Three agitated tanks with oxalic acid, belt filtration
- Metathesis: Sodium carbonate conversion at 90°C, belt filtration, drying
- Effluent treatment: Neutralisation to pH 8 with quicklime, thickening, filter pressing
- Off‑gas scrubbing: Flue gas desulphurisation with slaked lime
- Reagents handling: Rail, truck, and container delivery; on‑site dissolution and storage
Source: Preliminary Economic Assessment for the Ashram Rare Earths Project, 2026-05-29. Project website: Ashram Rare Earths Project
