To assess a mining investment, trace the mine-life and production forecasts back to the current technical report, reserve estimate, mine schedule and operating assumptions. Then test whether the whole production chain can support the forecast, whether an expansion is mature enough to rely on, and how returns change when price, grade, cost or schedule assumptions move. Treat operating results, approved plans and conceptual growth targets as different kinds of evidence.
Start with the latest disclosures and the right reporting rules
Find the issuer’s latest filed technical report and read it alongside subsequent material disclosures. A technical report is a dated account of a project and its assumptions, not a guarantee that every later company statement has been independently re-estimated.
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Record the report’s effective date, the qualified persons responsible, the project ownership and scope, the study stage, and whether a newer estimate or material change has been disclosed. Also identify the issuer’s primary listing and the disclosure regime that applies. Canadian NI 43-101 and U.S. SEC rules are separate frameworks; do not apply one jurisdiction’s requirements to an issuer or disclosure governed by another.
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Under NI 43-101, written disclosure of mineral resources and reserves identifies the estimate’s effective date, quantities and grades, key assumptions and methods, and known material risks. Technical-report filing obligations apply in specified disclosure circumstances; they do not mean that every public statement must have a newly filed report behind it. The Government of British Columbia’s NI 43-101 Form 43-101F1, Item 25, calls for discussion of significant risks and uncertainties that could reasonably affect confidence in resource or reserve estimates or projected economic outcomes.
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How long is the mine life?
Trace the schedule to reserves, not just resources
Mine life is the result of a mine plan built from inputs; it is not a standalone fact. Trace the scheduled extraction back to the disclosed reserve estimate and examine the reserve category, tonnage, grade, cut-off assumptions, conversion basis and mining method. Then check whether the schedule’s treatment of dilution, recovery and production rate is consistent with the estimate and the proposed operation.
Do not treat a mineral resource as interchangeable with a mineral reserve. Under the SEC study rules covered here, inferred resources are excluded from a pre-feasibility study’s demonstration of economic viability in support of reserve disclosure. An inferred resource cannot be converted directly into a reserve without new evidence first supporting a higher resource category. A long-range target that depends on material outside the reserves therefore has a different level of support from a schedule based on reserves.
Check the estimate’s date and assumptions
Compare the technical report’s estimate and schedule with later company announcements. Look for changes in resource or reserve quantities, mine sequencing, cut-off assumptions, processing plans or project scope. A mine-life figure from an older report may no longer describe the current plan if the underlying estimate or project has changed.
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Study stage matters because the detail behind the plan changes. The SEC rules reviewed distinguish pre-feasibility from feasibility by the detail and certainty of the modifying factors. Feasibility work addresses the finalized mining plan and schedule, construction and production ramp-up, process design and throughput, utilities, infrastructure and permitting in greater detail. A study label is useful context, but investors should still inspect the actual assumptions and unresolved work.
Can the mine meet its production targets?
Production depends on a connected operating chain, not a single headline capacity number. Compare the scheduled mining rate and sequence with the equipment and mining method, dilution, processing throughput, metallurgical recovery, product specifications and ramp-up assumptions. A shortfall or delay in any link can affect output, costs or timing.
Test the operating chain
- Ore supply: Does the mine sequence deliver the planned quantity and grade on the schedule assumed by the plant?
- Processing: Are throughput and recovery supported by metallurgical evidence? Consider whether test samples represent the deposit and whether deleterious elements or other processing factors could affect recovery.
- Utilities and site conditions: Review power, water, geotechnical assumptions and the workforce and logistics needed to sustain the plan.
- Waste and product movement: Check tailings and waste arrangements, transport capacity and any infrastructure needed to deliver saleable product.
- Ramp-up: Compare the planned transition to steady production with the construction, commissioning and operating steps described in the study.
These checks should connect to the actual mine schedule and project design. A plant’s stated nameplate throughput, for example, does not by itself establish how much saleable product the operation can produce at a given grade and recovery.
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Separate planned output from demonstrated performance
For an operating mine, compare guidance and planned rates with the issuer’s actual operating disclosures over time. Examine grade, throughput, recovery and interruptions alongside production, rather than treating a single period as proof of a sustained rate. For a project that has not begun operations, forecasts remain plans; technical studies can support their assumptions but cannot establish operating performance that has not yet occurred.
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How much production will an expansion add?
Assess incremental output as a separate case, not as an automatic extension of the base mine plan. Identify the specific constraint the project intends to remove: ore supply, mining rate, processing capacity, recovery, power, water, transport, tailings capacity or permitting. Then trace the added production to the additional capital, schedule and dependencies required to remove that constraint.
Distinguish the stage of the expansion
| Stage | What it tells an investor | What remains to establish |
|---|---|---|
| Conceptual target | A possible future production direction. | Whether a current technical plan, economic case, approvals, funding or execution path supports it. |
| Preliminary economic assessment (PEA) | An initial economic assessment of a proposed case. | Whether its assumptions will be realized and whether later, more detailed study work supports the plan. A PEA is not a pre-feasibility or feasibility study. |
| Pre-feasibility study | A more developed study than an initial assessment, with modifying factors evaluated at greater detail. | Whether remaining technical, economic, permitting and execution work supports advancing the project. |
| Feasibility study | A more detailed case addressing such matters as the finalized mine plan, construction, ramp-up, process design, utilities, infrastructure and permitting. | Whether the project is approved, financed and deliverable on its proposed schedule and budget. |
| Approved, funded, under construction or operating | Evidence of progress beyond a study-stage proposal; each status is distinct. | For an uncompleted project, whether construction and commissioning achieve the planned scope and production; for an operating project, whether actual results support the target. |
The categories describe different development states, not interchangeable assurances of success. A filed PEA for the Whistler project by U.S. GoldMining Inc., effective March 2, 2026, states: “The PEA is not a pre-feasibility study or a feasibility study.” The report also cautions that its assumptions mean there can be no certainty that the initial economic assessment will be realized. That is a project-specific warning, not a claim that every PEA has identical assumptions or outcomes.
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Identify what could delay or prevent the expansion
List the decision gates still outstanding and tie each to the added production case. Relevant dependencies can include reserve conversion, a plant debottleneck or new facility, power or water supply, transport, tailings capacity, permits, community arrangements, contracts and financing. Check the timing and capital assigned to these items, and whether the expansion economics include the costs of enabling infrastructure as well as the main project build.
NI 43-101 specifically calls for production economics when a technical report includes a material production expansion. Management targets and forward-looking production statements should therefore be tested against current technical work and execution evidence, rather than added uncritically to the base plan.
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Follow the economic model from annual production through annual cash flows. Review the assumed commodity prices, grades, recoveries, capital and operating costs, taxes, royalties and discounting. Check how those inputs interact with the production schedule: a delay or lower early-year output can affect value even if a headline mine-life estimate is unchanged.
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NI 43-101 calls for sensitivity or other analysis, as appropriate, using variations in commodity price, grade, capital, operating costs or other significant parameters. Read the sensitivities alongside the base case, and note which assumptions have the greatest effect on returns. A single valuation figure cannot show how robust the project is to those changes.
Read cost-estimate ranges in their rule context
| Study context in the SEC rules reviewed | Stated estimate criteria | How to interpret them |
|---|---|---|
| Pre-feasibility | Approximately ±25% minimum accuracy; contingency not exceeding 15%. | These are provisions for the specified study context, not evidence that a particular project will meet its budget. |
| Feasibility | Approximately ±15% minimum accuracy; contingency not exceeding 10%. | These are provisions for the specified study context, not a guarantee of final cost or schedule. |
Compare the project’s stated estimate accuracy and contingency with its study stage, and examine what the estimate includes. Treat the rule criteria as disclosure requirements for those contexts, not as independently measured real-world forecast performance.
How to compare mine plans or investment cases
When comparing alternatives, keep like with like. A current operating plan and a conceptual expansion are not equivalent cases, even if both are expressed as annual production. Label each case’s stage and assumptions before comparing it.
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- Annual production, grade, throughput and recovery profile.
- Study stage and the maturity of the cost estimate.
- Initial and sustaining capital, operating costs and cash-flow timing.
- Dependencies involving infrastructure, permits, community matters, contracts and markets.
- Sensitivity of returns to price, grade, cost and schedule changes.
These dimensions help distinguish a production forecast supported by a current reserve-based plan from one that relies on conversion, construction or other future decisions. No broad industry benchmark for mine-life accuracy, production forecast error or expansion success is established by the sources cited here, so an investor should not substitute an unsupported success rate for asset-specific diligence.
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