Mine Feasibility Study: What Each Stage Covers

A mine feasibility study is the backbone of any serious mine development decision. It’s not one document. It’s a staged series of technical and economic investigations, each with a different job: a scoping study screens, a prefeasibility study selects, and a definitive feasibility study commits. If you’re an owner or procurement manager, you’ll see these terms on every mineral processing EPC proposal, and you need to know what each stage actually covers. The three stages exist because capital for a mine is too large to commit on a single report. You build confidence in steps, and each step costs a fraction of the next one.

Scoping, prefeasibility and definitive feasibility: three different jobs

A scoping study is a preliminary technical and economic assessment that relies on limited data—often historical drilling, surface samples and analogy to similar deposits. It’s used to decide whether a project warrants the next round of expenditure. A prefeasibility study, by contrast, is an evaluation of a development option’s technical and economic viability. It adds infill drilling, preliminary metallurgical testwork and enough engineering to support a mineral resource estimate and a probable capital cost range. A definitive feasibility study is the final engineering and economic basis for a construction decision. It needs detailed engineering, firm vendor quotations, confirmed mining and processing plans, and a mineral reserve estimate, if the ore body supports one. You cannot skip a stage just because the ore looks rich; the missing data will catch you later.

The JORC Code and NI 43-101 don’t set numeric accuracy bands. They require that all material assumptions be disclosed and that the study’s confidence level matches its purpose. A scoping study is not a production decision document. A prefeasibility study supports a decision to spend more money. A definitive study supports a decision to build. That hierarchy is what keeps owners from committing hundreds of millions of dollars on a guess.

What data each stage demands

For a scoping study you need at least: geological mapping, a small number of drill holes, basic recovery assumptions and a conceptual flowsheet. For prefeasibility you add: representative composite samples for metallurgical testwork, geotechnical data for pit or underground design, water and power availability, and a preliminary mine schedule. For a definitive study you must have: detailed engineering drawings, capital cost estimates tied to supplier quotes, a full environmental and social impact assessment, and a reserve statement signed by a competent person. The rule is simple: the stage name tells you how much data sits behind the conclusions. Xinhai reports about 200 metallurgical test programs per year across more than 70 ore types, which is why many owners bring samples to a mineral processing EPC contractor before writing the next-stage report.

You’ll also need a block model at prefeasibility and a mine schedule at definitive. The block model quantifies tonnes and grade. The mine schedule sequences that ore through the plant. Without those, the economic model is just a spreadsheet with assumptions stacked on assumptions. Don’t let a consultant sell you a definitive study without a measured or indicated resource to support a reserve.

Who signs and what JORC and NI 43-101 require

Public reporting of mineral resources and ore reserves in Australia follows the JORC Code. In Canada, NI 43-101 relies on the CIM Definition Standards, published by the Canadian Institute of Mining, Metallurgy and Petroleum. Both codes require a ‘competent person’ or ‘qualified person’ to sign the report. That person must have relevant experience, belong to a recognised professional organisation, and take personal responsibility for the technical disclosure. A scoping study can be released under JORC, but it must be clearly labelled and must not state ore reserves. Prefeasibility and definitive studies are the normal basis for publishing a maiden ore reserve.

A mineral resource is a concentration or occurrence of solid material of economic interest in or on the Earth’s crust in such form, grade, quality and quantity that there are reasonable prospects for eventual economic extraction. A mineral reserve is the economically mineable part of a measured or indicated mineral resource demonstrated by at least a prefeasibility study. If you publish a reserve, the code forces you to show the modifying factors: mining, processing, metallurgical, infrastructure, economic, marketing, legal, environmental, social and governmental factors. That’s a lot, and it’s why many companies stop at resources.

Where metallurgical testwork fits

Metallurgical testwork is the hinge between geology and process design. It answers three questions: can the ore be concentrated economically, what recovery is realistic, and what equipment size is needed. The testwork sequence typically moves through three ordered stages:

1. Batch-scale tests on drill core or composite samples establish basic leach or flotation response.
2. Locked-cycle or variability tests on many samples map recovery across the orebody.
3. A pilot plant or integrated continuous run confirms the complete flowsheet under near-production conditions.

If you cut the pilot stage to save time, you’ll carry that risk straight into construction. Xinhai reports about 200 metallurgical test programs per year covering more than 70 ore types, according to the company’s published figures, and its 3,000 t/d gold plant in Guinea was built only after testwork confirmed the gravity and leach circuit.

For a copper project, the equivalent question is whether the copper beneficiation flowsheet can handle mineralogical variability. A few flotation tests will tell you the ore floats. They won’t tell you if the concentrate grade holds when the feed swings from oxide to sulphide. That’s why variability is not optional.

Why thin testwork breaks a bankable study

A feasibility study is only as good as the testwork behind it. If you base a definitive study on three bottle-roll tests, you don’t have a basis for reagent consumption, retention time or tailings characterisation. You’ll get a recovery number that looks precise but isn’t reproducible. Later, at commissioning, the plant will underperform the study’s figures. The fix is straightforward: spend more on variability testwork early, and don’t sign a definitive study until the flowsheet has been run continuously at a representative scale. Xinhai’s Zimbabwe 2 Mt/a spodumene project is an example where flotation proved difficult, and the process was switched to heavy medium separation after testwork, according to the company’s project brochure. That switch would have been impossible after construction.

Thin testwork also shows up in the capital cost estimate. If you don’t know the grind size, you can’t size the ball mill. If you don’t know the reagent types, you can’t size the tanks. The study’s cost accuracy is only as good as its process design, and the process design is only as good as the test data.

How the feasibility stages connect to EPC delivery

Xinhai reports more than 600 EPC+M+O projects across 100+ countries, according to the company’s published figures. That scale matters when you choose a contractor to carry your feasibility study into construction. An EPC contractor that has built plants on multiple ore types can spot feasibility-stage errors before they become site orders. The same team that runs the mineral processing EPC should review the definitive study’s process design, equipment list and layout. If the study was written without a contractor’s input, you’ll often find that the equipment selection doesn’t match what’s actually available or that the layout ignores maintenance access. That’s a common source of change orders later.

How to avoid the most expensive mistake

The most expensive mistake isn’t a bad recovery estimate; it’s signing a definitive study before the metallurgical data is sufficient. You can recognise the warning signs: a testwork report shorter than ten pages, no locked-cycle tests, no pilot run, and a recovery range wider than the margin on the project. When you see those signs, delay the feasibility stage and go back to the laboratory. If you’re evaluating an EPC proposal, ask for the testwork report and the qualified person’s sign-off. A credible mineral processing EPC contractor will show you the test data before it shows you the price.

Feasibility studies are not a checkbox. They are a risk filter. The earlier you bring in real metallurgical data, the cheaper the corrections. The later you find a flaw, the more it costs. You’ll sleep better if the study that supports your investment is built on testwork, not on assumptions.