Evaluation of Solid Mineral Deposits: Resources, Reserves and Project Economics

Mineral deposit evaluation is not a single calculation of how much ore or metal sits underground. It is a sequential analysis of geological data, ore quality, mining and processing conditions, infrastructure, risk and project economics. Reserve estimation is part of that work, but tonnage and grade alone settle nothing: the specialist first tests the reliability of the source material, reconstructs the logic of the exploration campaign, builds a model, and only then comments on whether the deposit has industrial potential and under what conditions that potential holds.

A full assignment may cover an audit of the source geological material, verification of sampling results, geological and block modelling, Mineral Resource estimation, reserve determination, analysis of processing and mining engineering factors, economic calculations and reporting. Each of these blocks is discussed below; what matters here is the order. Without verified data there is no model; without a model there is no resource estimate; without modifying factors there are no reserves; without a production scenario there is no economic case.

The point of the exercise is a decision, not a document. The evaluation should tell the client whether to continue exploration, where to place additional drillholes, whether the project can move to the next stage, how well the declared reserves are supported and which factors constrain the economics of extraction. For projects in Almaty and Almaty Region, the scope is set by the level of exploration maturity, the commodity and the purpose of the evaluation — the same conditions that apply anywhere else in Kazakhstan.

What deposit evaluation is, and how it differs from reserve estimation

Evaluation goes beyond the question of how much material lies in the ground. It also asks how reliable the source data are, how mineralisation is distributed, how much of the deposit has genuinely been tested, whether extraction is technically feasible and whether the project has an economic case. Most disputed results arise not from arithmetic errors but because one of those questions was never answered and a conclusion was drawn regardless.

The central distinction is between Mineral Resources and Mineral Reserves. A Mineral Resource is a concentration of material in the ground, identified and classified on geological grounds, with reasonable prospects for eventual economic extraction. A Mineral Reserve is the economically mineable part of an Indicated or Measured Resource, supported by modifying factors assessed to at least a pre-feasibility level of study. Converting resources to reserves is not a relabelling exercise: until the mining, processing, legal and economic assumptions have been worked through, the material cannot properly be called a reserve.

A third exercise should be kept separate from both. Geological evaluation addresses the architecture of the deposit and the quality of the geological base. Mineral Resource and Reserve estimation delivers a quantified result under a chosen reporting code. Valuation of the asset deals with the worth of the project or an interest in it and builds on resources and reserves already prepared. The data overlap; the objectives and the resulting documents do not.

The practical consequence is straightforward. A large volume of mineralised material does not by itself confirm economically mineable reserves. Grades, the mining method, dilution and losses, metallurgical recovery, distance to infrastructure and cost levels all bear on the outcome. A smaller deposit with robust economics is often the better asset.

When a full deposit evaluation is required

The triggers are few and all tied to a decision point:

• an exploration stage has been completed;
• new drilling results change the interpretation of the orebodies;
• resources need to be updated or re-estimated;
• a licence or a mining asset is under consideration for acquisition;
• investment or project finance is being raised;
• metal prices, processing technology or design solutions have changed;
• the project is moving from exploration to mine design;
• inconsistencies have been found in historical data.

Depth of work follows the decision at hand. A preliminary audit of archive material, a resource estimate, a report prepared for state registration purposes and a full techno-economic model differ several-fold in effort, and commissioning the largest scope where an audit would do serves no purpose — nor does the reverse.

Skipping the evaluation usually costs more than the evaluation itself: inflated expectations of the reserve base, an unfounded drilling programme, an unsuitable processing route, understated CAPEX and OPEX, a weak position in investor negotiations, and repeated work when the primary data fail verification.

Source data required for a deposit evaluation

Geological and exploration material

Work begins with whatever the licence holder already holds: geological maps and sections, collar coordinates for pits, trenches and drillholes, drilling logs, core logging records, assay results, density data, mineralogical studies, geophysical and geochemical surveys, and previous reports and estimates. Material from different periods and different contractors is normal, but it has to be reconciled.

The specialist checks consistency rather than the presence of files: whether a single coordinate system was used, whether collars were surveyed correctly, whether duplicate samples or intervals exist, whether data provenance can be traced and whether the chain from the primary sample to the laboratory result can be reconstructed. A geological database in which that chain breaks limits the achievable resource category regardless of how much drilling has been done.

Sampling and laboratory quality

QA/QC is not one line in a report but several independent control loops. Certified reference materials and blanks travel with the sample stream. Field duplicates, coarse-crush duplicates and pulp duplicates are collected separately, each at the relevant stage of sample preparation. To these are added internal laboratory checks, umpire assays at a second laboratory, and the security and representativity of the core, including storage conditions and the way core is placed in trays.

Weak control does not show up immediately. Unreliable assays distort the interpretation of orebodies, average grades and the boundaries of mineralised domains, and ultimately the resource classification. The company links drilling, sampling and core preservation quality to the reliability of the geological model and of the reserve estimate: the gap between an elegant model and poor primary data surfaces during audit, and sometimes only during mining.

Additional data

Converting resources to reserves and running the economics requires a further layer: topographic control, hydrogeological and geotechnical conditions, metallurgical test work, host rock properties, environmental constraints, existing infrastructure and access to power, water and transport.

An early resource estimate may not need all of it. Yet these are the inputs that decide whether a well-graded deposit is profitable: slope stability drives the strip ratio, ore amenability drives recovery and concentrate quality, and remoteness can erode margin faster than a change in the metal price.

What to provide a consultant for a preliminary review

• the licence or contract and the boundaries of the subsoil plot;
• a drillhole summary with coordinates and downhole surveys;
• assay data referenced to intervals;
• laboratory certificates and QA/QC results;
• core logging records and information on core preservation;
• topographic base and density data;
• previous reports and estimates, including archive material;
• details of any metallurgical test work already carried out;
• the purpose of the evaluation and the intended reporting standard.

Stages of a mineral deposit evaluation

Data collection and audit

The first task is an inventory: what material exists, in what format, which periods of work it covers, by which methods it was obtained and whether data from different contractors and exploration phases can be combined. Discrepancies between Soviet-era reports and modern drilling are common and call for a considered decision rather than a mechanical merge of tables.

The audit delivers a list of usable data, the contradictions identified, the critical gaps and recommendations for further work. Not every deposit can be evaluated in full from archive material alone: where primary documentation has been lost and sample traceability cannot be re-established, some conclusions will need confirmatory drilling or resampling.

Geological interpretation and modelling

Interpretation describes the geology of the deposit: the shape and attitude of the orebodies, structural control on mineralisation, lithology, alteration zones and the distribution of valuable components. At this point the interpretation is also tested against geophysics and core observations, not against assays alone.

A three-dimensional geological model follows — wireframes of the orebodies and the definition of geological or estimation domains. A domain should group material with similar geological and statistical characteristics. Where a mineralised zone and weakly mineralised host rock fall inside one wireframe, the statistics within the domain cease to be homogeneous and any grade interpolation smears grade across the volume.

The model is not a presentation graphic. Volumes, average grades and the assessment of uncertainty all depend on it, so wireframe geometry and domain boundaries are documented as rigorously as the assay data.

Mineral Resource estimation

Data preparation covers compositing to a uniform length, outlier analysis and any decision on top-cutting, density assignment, statistical analysis by domain, study of spatial variability through variography, and selection of the interpolation method. Each choice affects the result, so the reasoning behind it — not merely the choice — belongs in the report.

The block model comes next. Each cell is assigned geological and quantitative attributes — domain, density, estimated grade — and tonnage and contained metal are calculated from these within the reporting outline. Block size is matched to the drill spacing: an over-fine block creates an impression of detail the data do not support.

Classification closes the stage. Inferred, Indicated or Measured status depends on data density and quality, geological continuity, confidence in the interpretation and the outcome of model validation. Classification is the Competent Person's judgement, and it should be explained in the report rather than simply asserted.

Reserve estimation

Reserve estimation differs from the preceding stage in subject matter: what is assessed is not the quantity of material but its technical and economic recoverability under specific design solutions. The same model block may sit inside reserves in one mining scenario and outside them in another. Probable Reserves are derived from Indicated Resources and, in certain cases, from Measured Resources where uncertainty in the modifying factors prevents the higher category being assigned; Proved Reserves are derived from Measured Resources only. Downgrading on conversion is permissible; upgrading is not.

Modifying factors are conventionally grouped as mining, geotechnical, hydrogeological, processing, environmental, legal, infrastructural, marketing and economic. In Kazakhstan the legal group carries no less weight than the technical one: licence terms, the conditions attached to design documents and rehabilitation obligations bear directly on how much of the resource can be mined at all.

Particular attention goes to mining losses and dilution under the selected mining method, metallurgical recovery for each component, planned throughput, the extraction method — open pit or underground — and constraints on pit slope or underground opening stability. These parameters turn a geological outline into recoverable reserves, and they are also the ones most often revised at the next iteration of the project.

Techno-economic evaluation

Moving from model to production scenario sets everything downstream: mining method, throughput, mining sequence, waste stripping and development volumes, processing route and saleable product range. The production schedule ties these decisions to a timeline and determines when the project begins to generate cash flow.

A revenue and cost model is then built: capital expenditure, operating costs, recovery, realised prices, transport, infrastructure costs and the obligations imposed by the project, including environmental payments and closure provisions.

A single optimistic set of assumptions proves very little. Robustness is tested across several scenarios, and the spread between them is usually more informative than the base case number itself.

Reporting and recommendations

The report records data sources, methodology, assumptions adopted, limitations, the models used, calculation results, resource or reserve categories and sources of uncertainty. This section determines whether a third party — auditor, investor or government body — can reproduce the reasoning.

The practical section answers the client's questions: which data need to be confirmed, where additional drilling is required, which test work is necessary, whether the project can advance to the next stage and which parameters most influence the outcome. Without it the report describes rather than informs planning.

Estimation methods

The method is chosen on the properties of the deposit — its architecture, orebody geometry, style of mineralisation, grade distribution, drill spacing and data quality — not on familiarity with a software package. An approach that performs well on a continuous tabular body may show material bias on a vein system with sharp contacts.

The available approaches are well known: geological block and mining block methods, polygonal methods, inverse distance weighting, geostatistical estimation, kriging, and conditional simulation for assessing uncertainty. A method-by-method treatment belongs in a textbook; for an evaluation, what matters is that the choice is justified by the data and then verified.

Verification is done through model validation: visual comparison of the model against the sample data, comparison of input and estimated grades, checks by direction and elevation, analysis of global and local bias and, where production data exist, reconciliation against actual mining results. Confidence in an estimate rests on validation, not on the standing of the method.

Ore deposits and metal deposits: points of difference

Ore deposit evaluation

The difficulties with ore deposits arise from geometry and variability: orebodies are irregular, grades are unevenly distributed, mineralisation is structurally controlled, oxide zones with different metallurgical behaviour occur, contacts are frequently sharp, and ore and host rock densities differ appreciably. Each of these sets its own requirements for sample spacing and domain construction.

Approach depends on deposit type. A gold deposit with coarse free gold demands attention to the nugget effect and the sample preparation protocol; a porphyry copper deposit to scale and cut-off grade; an iron ore deposit to concentrate quality and deleterious elements; nickel-cobalt ores to mineralogy and recovery. The key parameters and risk factors differ, and transferring a methodology between types without testing it is unwise.

In evaluating metal deposits, spatial grade variability, mineralogy and the metallurgical recoverability of the valuable components carry particular weight. Those three characteristics govern both the resource category and the credibility of the economic model.

Polymetallic deposit evaluation

The defining feature of polymetallic mineralisation is that principal and by-product components are distributed unevenly within the orebody. Lead-zinc ores with by-product silver and copper may show different anisotropy directions for each metal, and estimating them with a single variability model is not defensible.

Each component is treated separately for grade, correlation with the other components, mineralogical form, metallurgical recovery under the intended flowsheet, concentrate quality, payable and penalty elements, and the possibility of producing more than one saleable product. Polymetallic recovery often shifts project economics more than an increase in tonnage.

Metal equivalent grade is a convenient way of presenting combined economic value, but the formula must rest on defensible prices, realistic recovery for each metal and actual concentrate terms. An equivalent calculated without recovery overstates the value of the ore and misleads the licence holder first of all.

Hence the central risk: a large total metal endowment does not guarantee a viable project. If individual components report poorly, deport to the wrong concentrate or attract penalties on delivery, part of the declared value stays on paper.

Economic evaluation of a deposit

Economic evaluation binds the geological model, design solutions, processing technology and financial assumptions into a single calculation. It shows under what conditions the project is economically viable and how attractive it is to an investor under differing assumptions.

The inputs are fixed in advance and recorded in the report: production volume, component grades, strip ratio, losses and dilution, metallurgical recovery, throughput, capital expenditure, operating costs, product prices, logistics and infrastructure, and the construction and ramp-up schedule.

The performance measures serve different purposes, and none of them tells the whole story alone. Net present value (NPV) shows the value added by the project with the time value of money taken into account. The internal rate of return (IRR) restates the same outcome as a rate comparable with alternatives. Payback and discounted payback address the horizon over which the investment is recovered. Annual cash flow shows whether funding is sufficient at the peak of construction. Unit operating cost and the break-even point determine the metal price at which the project remains viable.

Scenario and sensitivity analysis test robustness. Base, conservative and optimistic cases are supplemented by single-factor checks: metal price movement, CAPEX and OPEX escalation, lower recovery, delayed start-up, throughput shortfall. Economic risk in a mining project rarely arrives from one direction, so combinations of factors matter too.

An evaluation of the efficiency of developing a deposit should show not only the calculated return but also how far the project can absorb changes in its key assumptions.

The parameters that move deposit economics most

• realised product price and concentrate payment terms;
• metallurgical recovery of the valuable component;
• grade in the blocks scheduled for mining and the cut-off grade adopted;
• strip ratio and the mining method selected;
• capital expenditure and time to full capacity;
• transport and infrastructure costs;
• mining losses and dilution.

Reporting standards in Kazakhstan

The KAZRC Code sets common principles for the public reporting of exploration results, Mineral Resources and Mineral Reserves in the Republic of Kazakhstan. Conclusions in such reporting are made by a Competent Person, who carries professional responsibility for them. The requirements attach to relevant experience: a professional organisation recognised for the purposes of the Code — in Kazakhstan, PONEN, the Professional Association of Independent Subsoil Experts — confirms a specialist's standing, and that experience must relate to the commodity and deposit style covered by the report. The QMR accreditation (Qualified for Minerals Reporting), awarded in Kazakhstan by PONEN to its professional members, confirms fitness to contribute to public reports but does not in itself confer Competent Person status: the requirements of the applicable reporting regime are assessed separately.

International practice rests on several documents, and they are not interchangeable. JORC is the Australasian code for public reporting, alongside the other codes in the CRIRSCO family. NI 43-101 is a Canadian disclosure instrument for issuers rather than a reporting code, and the practitioner acting under it is a Qualified Person. The choice of format depends on jurisdiction, the purpose of the report, investor requirements and the disclosure venue; the international reporting standards are aligned in principle but not identical in procedure.

State registration in Kazakhstan is a separate line. The Rules for the submission and consideration of applications for solid minerals extraction licences tie an exploration licence holder's exclusive right to the discovery of a deposit whose resources and reserves are supported by a report on the estimation of solid mineral resources and reserves. The design documents for each stage are defined by the Code on Subsoil and Subsoil Use (No. 125-VI of 27 December 2017): the exploration plan under article 196 and the mining plan (PGR) under article 216. The specific procedure for entering data into state records should be checked against the current version of the regulations and against the licence conditions, since both the wording and the practice of the authorised body have changed over time.

The reporting standard is best settled before work begins. It governs the composition of the input data, QA/QC requirements, the depth of justification, the qualifications of those involved and the structure of the final report. Changing standards late almost always means returning to the data and rebuilding part of the document.

What the client receives

The deliverable depends on the assignment. In its fullest form it comprises an opinion on the quality of the source data, a structured geological database, three-dimensional geological and block models, a Mineral Resource estimate with classification, a reserve estimate where exploration maturity allows, an economic model, sensitivity analysis, a risk register, recommendations for further work and a technical or public report.

Each of these ties back to a management decision: whether to continue or halt exploration, where to place further drillholes, which mining option to study in more detail, whether test work is required, whether the project can move to feasibility study and design, how well the stated asset value is supported, and what to place before an investor.

A good report sets out not only the final figures but the limits within which they hold. A statement of the assumptions under which the result ceases to be valid carries more weight with specialists than a neatly formatted table without caveats.

What drives timing and cost

Effort is driven by the number of drillholes and samples, the format and quality of the database, the availability of primary documentation, the size and complexity of the deposit, the number of valuable components, the exploration stage and the need to recover historical data. The difference between a clean digital database and boxes of paper logs is measured in weeks.

Timing is further affected by any need for resampling, additional laboratory work, field programmes, geotechnical and hydrogeological investigations, metallurgical test work and the reporting standard required.

Pricing on licence area or drillhole count alone rarely works: deposits that look comparable on paper can differ severalfold in effort. A preliminary review of the material comes first, and the scope of work is defined from its findings.

To establish a preliminary scope, schedule and cost, the client provides the available geological material and states the purpose of the evaluation.

Deposit evaluation in Almaty and Almaty Region

Reserve estimation for deposits in Almaty Region follows the same methodology as elsewhere. In practice the service takes several forms:

• review of projects located in Almaty and Almaty Region;
• remote work with digital geological material;
• site visits where core, workings or ground conditions need to be inspected;
• coordination of field, laboratory and design work.

The administrative centre of a project and the subsoil plot are often in different regions — the licence holder's office may be in Almaty while the licence area lies well outside the city — and the working arrangement is built around that geography. Geological consulting in Almaty differs little in this respect from work on projects elsewhere in Kazakhstan: licence holders generally transfer digital material, and site visits are planned around specific tasks.

Minerals Operating's regional project experience is evidenced by work at the Dalabay deposit: the website lists a mining plan for gold and silver extraction, an exploration extension plan for the eastern flank, and environmental documentation. This is evidence of design and project support, not of a full reserve evaluation unless separately confirmed.

Minerals Operating's experience in resource and reserve estimation

Minerals Operating provides technical consulting in mineral resources and reserves, prepares reports under the KAZRC Code and engages specialists holding QMR accreditation. Resource estimation work is linked to exploration, mine design and economic analysis, and covers ore deposits of various types, from gold to iron-bearing. Mining projects in Kazakhstan differ in stage and in the state of their source material, so the scope is shaped around the individual deposit.

Assignments listed on the company's website include a report on Mineral Reserves and Mineral Resources at the Ayat deposit under the KAZRC Code, together with KAZRC Mineral Resource estimates for the Zholymbet, Atansor and Zapadny Karazhal deposits. These descriptions do not extend beyond the scope stated on the website.

For a preliminary review, Minerals Operating's specialists will examine the available material, identify critical gaps and propose a scope of further work.

Frequently asked questions

What does a full deposit evaluation include?

It combines a geological component — interpretation and modelling; a resource component — estimation and classification; a mining engineering component — extraction method and modifying factors; a metallurgical component — amenability and recovery; an environmental component — constraints and obligations; and an economic component — the revenue and cost model. The mix depends on project stage: early on, some blocks are carried out at a preliminary level or not at all.

How do Mineral Resources differ from Mineral Reserves?

A Mineral Resource is a concentration of material in the ground with reasonable prospects for eventual economic extraction, classified by geological confidence. A Mineral Reserve is the economically mineable part of an Indicated or Measured Resource, arrived at after modifying factors — mining, processing, infrastructural, environmental, legal and economic — have been assessed. Without that assessment, conversion does not take place.

Can a deposit be evaluated from archive material?

A preliminary audit and part of the modelling can be. Sufficiency depends on the quality, completeness and traceability of the data: where primary logs, assay certificates and collar surveys survive, a great deal can be recovered. Where primary documentation is lost or sampling is in doubt, confirmatory drilling or resampling will be needed.

How is the efficiency of developing a deposit assessed?

The production scenario is fixed first: mining method, throughput, production schedule and processing route. Recovery, realised prices, CAPEX and OPEX are then set. A discounted cash flow model is built on that basis and NPV, IRR and payback are calculated. Sensitivity analysis against the key assumptions completes the exercise.

How are polymetallic deposits evaluated?

Each component is estimated separately, with its own variability model, recovery and flowsheet position. The economic contribution of each metal is then assessed against concentrate quality, payable and penalty elements and delivery terms. Metal equivalent grade is used to present the result, not to replace the component-by-component calculation.

KAZRC or JORC — which standard applies?

That depends on the purpose, audience and applicable requirements. KAZRC is intended for public reporting in Kazakhstan. JORC and other CRIRSCO-family codes apply in their respective jurisdictions and markets, while NI 43-101 governs disclosure about mineral projects in Canada. The requirements of the relevant regulator and trading venue should be checked before work begins.

How long does a reserve estimation take?

There is no universal figure. Duration depends on the volume and condition of the data, the complexity of the deposit, the number of components, any need for field or laboratory work, and the reporting standard required. The sensible sequence is a preliminary audit, from which a realistic schedule for each block of work can be built.

Is new drilling necessary?

That depends on drill spacing, the quality of the historical data, geological complexity and the resource category being sought. Where historical data fail verification or the spacing does not support the required confidence, confirmatory or infill drilling is set. Sometimes resampling of surviving core is enough.