The MRE was transformed into a diluted, regularised, mining model inclusive of mining recovery, by Orelogy Mine Consulting.
Reconciliation between the two models was considered acceptable, and the inbuilt dilution and mining recovery reflect the historical values of 17% dilution and 94% mining recovery which were derived from site model to process plant reconciliations.
If no site visits have been undertaken indicate why this is the case.
The Code requires that a study to at least Pre-Feasibility Study level has been undertaken to convert Mineral Resources to Ore Reserves. Such studies will have been carried out and will have determined a mine plan that is technically achievable and economically viable, and that material Modifying Factors have been considered.
The FS has addressed all material Modifying Factors required for the conversion of Mineral Resources to Ore Reserves and has shown that the mine plan is technically achievable and economically viable. Where possible and appropriate, the FS has used parameters in line with the current operations.
The economic cut-off grade calculation is approximately 0.2% Li2O, but the more conservative cut-off grade was adopted based on historical operating experience as an approximation of the practical process plant recovery constraint.
The addition to the specific modifying factors described in the sub-sections below, the optimisation data inventory and input parameters included:
- Regularised mining model created from the MRE that included dilution and mining recovery
- Surveyed surface topography provided from Mt Cattlin as at 01/07/23
- Contract mining costs from a competitive tender process
- Closure costs from the site Mine Closure Plan cost estimate
- Spodumene concentrate (SC5.4) revenue price of US$1,500/t inclusive of shipping and marketing costs
- Tantalite concentrate revenue from current sales contract
- State Government and third-party royalties
- Processing, General & Administration, concentrate surface haulage, and port costs from current site budgets and forecasts (based on actual data)
- Net Present Value (NPV) discounting rate of 10%
Where supplied by Allkem, these input parameters were reviewed by Entech and considered appropriate for the current spodumene concentrate market.
The staged pit design and schedule is considered suitable for Ore Reserve estimation.
The mining methodology is a continuation of the conventional hard rock open cut practices of the current operations with continuous drill, blast and excavate cycles (with ore grade control as required).
The existing operations provide access to the operations of the ORE.
97% of the rock within the pit containing the ORE is competent fresh (unweathered) material, and key design parameters derived for fresh rock were:
- 20 m bench height
- 70o bench face angle
- 8.5 m wide spill berm
- 52o inter-ramp angle
- 12 m wide geotechnical berm every approx. 100 m of high wall face
Pit designs were reviewed by Entech’s Principal Geotechnical Engineer to ensure compliance with geotechnical intent.
In conjunction with the Mineral Resource and grade control predictive computerised block models, established site grade control procedure utilises visual inspection of blast hole cuttings and pit-floor visual geological control when mining ore (“ore spotting”). The combination of techniques enables identification and segregation of barren pegmatite or pegmatite containing fine grained spodumene, from pegmatite containing coarse grained spodumene (ore). Specific grade control drilling campaigns (RC technique) are used in areas of higher structural or mineralogical uncertainty.
Mt Cattlin is an operating mine with current production and excavation knowledge. The resource drilling that defines the Stage 4 expansion is +95% Reverse Circulation (RC), and predominantly spaced at 40 m x 40 m.
- Regularising the block size into Selective Mining Unit (SMU) dimensions of 5.0 m x 5.0 m x 2.5 m (East, North, Elevation).
- The SMU size was selected based on the size of the equipment, the parent and sub cell block sizes in the resource model and matched the existing mining bench height to the vertical dimensions of the block.
- The ore blocks were flagged as either “Clean” (uncontaminated with mining dilution) or “Contaminated” (contaminated with basalt country rock and requiring beneficiation by optical sorting prior to being processed) ore types depending upon the proportion of clean ore within the SMU block.
- The overall model reports 82% of the ore to the Clean category and 18% to the Contaminated category.
The designed pit inventory has 0.5% of Inferred Mineral Resource which has been treated as waste for the economic assessment. The design of the pit is not sensitive to the inclusion, or not, of Inferred Mineral Resource.
Several ancillary circuits have been added over the life of the plant including optical ore sorters and fines recovery to incrementally enhance project economics. All the processing technology has been in use in this or other configurations for numerous to many years and are not regarded as novel.
Fine grained spodumene recovers poorly in the Mt Cattlin processing plant. The underlying MRE model has explicitly domained the fine-grained material and excluded it from the new in-situ MRE inventory.
Confirmatory metallurgical test work on ore in the Stage 4 extension is in progress.
A regression formula developed from historical operating performance that uses head grade to predict plant recovery, for a given grade of concentrate, is in daily use at Mt Cattlin. The Feasibility Study has used this algorithm to calculate metallurgical recovery in the economic analysis.
Key potential risk areas include noise, vibration and air emissions/quality are regulated, and have specific management plans to ensure compliance.
Waste rock and processing tails stored on site are classified as Non-Acid Forming (NAF) and chemically benign. The waste rock is predominantly unweathered (fresh), competent, basalt and andesites which form stable and erosion resistant landforms. Mt Cattlin pegmatite tailings are a coarse, sandy, material that drains readily and exhibits excellent stability on placement. The Heavy Media Separation process used to produce spodumene concentrate does not introduce chemicals into the tailings stream.
A 2023 Mining Proposal for pit and waste dump expansion required for part of this ORE has been submitted to the WA regulator, with approval expected in the third quarter of 2023. Further approvals will be required during the life of this ORE, potentially including pit and waste dumping area increases and a new In-Pit Tailings Storage Facility.
There is no reason to expect that all required approvals cannot be gained in sufficient time to allow the exploitation of this ORE as planned.
Accommodation is based near site for a mixed commute and residential workforce. The operation has access to a nearby regional bituminised airstrip capable of landing 100-seat jets. Sealed roads link the site to Perth, and major regional towns.
- contract mining costs – competitive market tender
- all other operating costs – from analysis of the site FY24 forecast (which is derived from actual historical costs and existing contracts)
The charges are not material in the overall pricing.
A flat 0.70 USD:AUD exchange rate was used in the cashflow modelling that was provided by Allkem.
The product revenue price used was discounted to be net of sea freight.
The spodumene concentrate commodity price used in the cashflow model is based on pricing by an external independent market forecaster, with appropriate modifications for Mt Cattlin product specification. Allowances have been made for surface and sea freight charges based on current site budgets and forecasts. The realised price (i.e., FOB; net of charges) forecast over the likely period the product from this ORE will be sold into market has an average of A$2,978/dmt and a median of A$2,963/dmt.
Minor revenue is derived from the sale of a by-product Tantalite concentrate and the sale price used is based on current contracts which average approximately A$35/ dry lb.
Transport charges are derived from existing contracts, and likewise penalty charges are taken from existing sales contracts.
The demand for spodumene concentrate is primarily driven by automotive batteries, and the underlying strong global growth in electric vehicles. From extreme deficit in supply over the past two years that has seen steep price growth and incentive for new supply, it is forecast that the overall market is moving into surplus, with intermediate fluctuations, until the end of the decade, from where it will again retreat into deficit.
The accuracy of these forecasts will be dominated by the accuracy of the assumptions quantifying the rate of growth in mine supply, and the rate of growth of EV sales.
During the market window applicable to this ORE, the Mt Cattlin product moves from being fully contracted, to a mix of contract and spot market exposure, to fully available for spot pricing. This mix of contract vs. spot markets exposure is subject to continuous review and adjustment.
Significant global supply chain diversification is underway which is seeing new lithium processing plants being developed in countries other than China, adding diversification to the potential customer base.
The optimisation price selected of US$1,500/t of spodumene concentrate was conservatively lower than the average pricing forecast of the likely market window. The cashflow model pricing used was based on the current forecasts for the likely market window, modified for the specification of the Mt Cattlin product, as discussed above in the Revenue
Factors section. It is assumed that all product produced is sold into existing contracts and spot markets.
Customer specification and acceptance of the product rely on a typical process of samples taken by an independent agency and conformance of the assays obtained by both the seller and buyer to an allowable range of variance.
Mining costs were derived by a competitive market tender process based on a designed and scheduled pit, and existing site infrastructure. Processing, General & Administration, product haulage, port, and shipping costs reflect corporate forecasts based on historical site actual data modified for Allkem’s view on FY24 market conditions.
As an ongoing operation, capital costs were relatively minor but included an allowance for developing a new In-Pit Tailings Storage Facility (IPTSF) during the life of mine, buffering land purchases, as well as ongoing sustaining capital. An end of mine allowance of $17.5 M has been incorporated into the economic analysis.
The overall cost base assumptions and analysis methodology are considered appropriate, robust and at FS level of accuracy.
Stripping Ratio is generally a proxy for risk, and the individual stages of the overall project (as currently evaluated) have quite different stripping ratios than the overall project average. The NPV sensitivity to key variables is therefore significantly different if analysed by stage. If the most sensitive stage (Stage 4-1) is assessed by the most influential variable (Revenue) at the most negative value (-20%), the cashflow is weakly positive whilst the NPV falls to zero. The following stage (Stage 4-2) and the sum of the two stages (Stage 4-1 + Stage 4-2) remain with strongly positive cashflows and NPV’s when Revenue is tested at -20%.
- Environmental Policy
- Requirements of approvals, permits and licences
- Environmental responsibilities of site personnel
- Site induction programmes
- Environmental monitoring and reporting requirements
- Inspection and audit process
- Non-conformance, corrective action, and risk management of incidents
- Preparation of procedures and work instructions addressing identified elements such as dewatering, saline spillage, waste management and bioremediation
- Stakeholder consultation, including:
- Regular update meetings with Shire of Ravensthorpe and Ravensthorpe Business Association
- Ongoing consultation with local neighbours
- Ongoing consultation with Traditional Owner groups and presentations at the Southwest Aboriginal Land and Sea Council working party meetings
- Appointment of an Environmental and Community Liaison Officer
- Biannual presentations to the Ravensthorpe community
- Establishment of the Mt Cattlin Community Consultation Group in 2018 with members consisting of respected leaders of the community and Mt Cattlin senior management. Minutes of meetings and presentations are made publicly available via https://www.mtcattlin.com.au/ccg/
Allkem have advised the Competent Person that there are no current issues that would be expected to endanger the ‘social licence to operate’.
The TSF design has included analysis of performance under seismic conditions, which was found to be acceptable.
The life of the ORE at less than five years is considered too short to be meaningful affected by longer term climate change. Short term variability in the form of floods or droughts is unlikely to materially affect the operation.
The site continued operating through the recent global pandemic.
All required permits for the current Stage 3 works, which represents approximately 40% of this ORE, are approved and are in place.
A Mining Proposal that describes the first phase of the Stage 4 expansion has been submitted to the WA Regulator for approval, which is expected in August 2023. In addition to the usual technical and regulatory compliance assessment that defines Mining Proposal assessment, a tenement status conversion from an Exploration Licence (E) to a General Purpose Licence (G) is required to enable waste dumping as a permitted activity, and the Mining Proposal to be subsequently approved. The E is held by Allkem and is in good standing, and the conversion to a G is expected to happen in May 2023 as per standard procedure in the timeframe estimated for overall Mining Proposal approval.
Post receipt of the Mining Proposal approval described above, subsequent permitting applications will then be made for the second phase of the Stage 4 expansion, including the next In-Pit Tailings Storage Facility (IPTSF). The second phase approvals are expected to be gained by the end of the first quarter of 2024, allowing sufficient time, including contingency, before the planned works are required to commence.
The surface stockpiles are classified as Probable Ore Reserves to simplify reporting. Some stocks such as ROM ore would normally qualify as Proved, but the downgrading is not material to the ORE.
The level of work undertaken through the FS is considered sufficient for the classification of Proved and Probable Ore Reserves.
Entech have undertaken internal peer review during the process.
The overall accuracy of the cost estimate used in the ORE is considered to be ±15%. The cost estimates have been derived from competitive market tender for mining costs, and actual site operating data for processing and General and Administration (G&A) costs, so the global accuracy is considered robust.
The current South-East In-Pit Tailings Storage Facility (SE IPTSF) capacity will be reached by the second-half 2024, and deposition will switch to the nearby NE IPTSF, which will have capacity for the remainder of the life of mine. The detailed design, costing and permitting of the NE IPTSF has not yet been finalised. Whilst the NE IPTSF capital expenditure (capex) is immaterial in the overall project cashflow, the estimation has been conservatively calculated and is at a PFS, rather than FS-level of accuracy. There is no reason to expect that permitting approvals will not be gained for the proposed NE IPTSF when applied for.
The Probable ore stockpiles include 900 kt @ 0.8% Li2O of tailings from early project life that are planned to be retreated at mine closure. The economic analysis test has used conservative metal recovery (30%) and product grade specifications (4.5% Li2O) indicated from metallurgical test work to date. Test work is continuing and flowsheet development is also underway but currently the level of accuracy is PFS rather than FS. The contribution of the tailings retreatment at mine closure is not considered material to the overall project.
Historically disproportionate amounts of fine-grained ore in the ROM feed negatively affected plant recovery in the second half of 2022. This has since been identified in the Mineral Resource and domained out of the new MRE which underpins this ORE.
Processing plant throughput and recovery data has been derived directly from production data, and therefore compare very well.
The mining model used to evaluate the ORE incorporates regularised blocks at SMU size, and mining dilution and mining recovery derived from actual production data and plant reconciliations. This new mining model has only been used in three month-end reconciliation at this point in time. The new model is expected to continue to reconcile well due to the technical improvements described above.
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