Reviewing mining projects from discovery through to operations, there’s one issue that comes up time and time again: resource classification. Teams spend countless hours on estimation methods and geological interpretation, only to fall short when it comes to correctly classifying the resource. Why does it happen? Optimism bias (often driven by board or funding expectations) Time pressure at the end of a study Inexperience with classification standards Or simply underestimating how critical classification really is As an external reviewer, here are a few practical principles that consistently separate robust resource models from risky ones: 🔹 Let drill spacing lead the classification Be strict. If there are spacing gaps, classify them accordingly. No “spotted dogs”. 🔹 Avoid circles around drill holes Resources aren’t radial. Use orebody knowledge and geological controls to define realistic shapes. 🔹 Data integrity matters QAQC results, core recovery, and missing samples must be reflected in the classification. Confidence in tonnes starts with confidence in data. 🔹 Respect the limits of your estimation parameters Search radii, variography, and interpolation choices should cap — not inflate — classification confidence. 🔹 Classify waste properly If the drill spacing supports a measured ore classification, the same logic applies to internal waste. Mining companies want to know where measured waste is — ironically, we mine far more waste than ore. Resource classification isn’t a tick-box exercise. It’s a risk statement, and decision-makers rely on it more than we often acknowledge. Get it right early, and everything downstream — mine design, scheduling, economics — becomes stronger. Happy to discuss or hear how others approach this challenge in their projects.

Jour 13/30 du Challenge 📘 Fiche Exercice N°13 : Krigeage de bloc – Du support ponctuel au support volumique en estimation minière ✍️ Ing. NGUEYAP AMBANI AUGUSTIN SERGE (Ingénieur Géologue – Spécialiste) Cette fiche présente : 1. Objectif de l’exercice 2. Rappel mathématique fondamental 3. Mise en contexte géoscientifique 4. Données fournies 5. Questions 6. Corrigé détaillé et commenté 7. Transition vers la géostatistique 8. Application pratique (R / Python) 9. Synthèse 10. Remerciements et perspectives 🙏 Merci à toutes celles et ceux qui aiment 👍, commentent 💬 et partagent 🔄 ce contenu. Votre soutien nous permet de continuer à proposer des formations de qualité. 🤝 Nous restons disponibles pour échanger et collaborer avec toute personne intéressée par ces thématiques.

Most mineral asset valuations are signed off by practitioners with dangerous gaps in at least one of three critical disciplines: 👉 Resource estimation science 👉 Commodity economics 👉 Financial management The codes permit it. The markets absorb the consequences. It’s time more is demanded from the profession. 🫵 Rigorous, integrated understanding is not optional — it is the baseline of competence. Defensible mineral resource estimation and valuation requires mastery across three distinct but inseparable disciplines: 👉 Geostatistical estimation and its inherent limitations 👉 The distinction between geological confidence, grade continuity, and grade uncertainty 👉 The economics and financial management that underpin mineral asset valuation 🫵 This is not just a technical problem — it is a systemic weakness in the global framework for mineral asset governance. How confidence limits are established, why estimated grade parameters differ from global sample statistics, why classical statistics form the inviolable ceiling of estimation certainty, and why the dangerous conflation of geological confidence with grade estimation uncertainty persists — all of it points to the same conclusion: The separation of mineral resource reporting codes from valuation codes, combined with the absence of formal economic and financial competency requirements, is a risk the profession can no longer afford to ignore. 📄 Full essay below.

Fiche d'Exercice N°2 Thème: Covariance et Corrélation Spatiale Analyse de la Continuité des Formations Géologiques Poursuivons notre série sur l'application des mathématiques en géosciences. La maîtrise de la covariance et de la corrélation spatiale est essentielle pour une modélisation géologique fiable et la prédiction des caractéristiques du sous-sol (géostatistique). Téléchargez cet exercice gratuit pour renforcer vos compétences pratiques. Commentez MATHS pour recevoir le lien instantanément. hashtag#Géostatistique hashtag#Géosciences hashtag#Modélisation hashtag#CorrélationSpatiale

It all began in the South African gold mines in the 1950s. An engineer named Danie Krige was frustrated by the inaccuracy of reserve estimates. The manual methods of the time were subjective, inconsistent and led to costly mis‑judgements. The problem was simple yet crucial: how could one estimate the grade of millions of tonnes of ore based on only a few hundred drill holes? 🔹 The solution came from France: Georges Matheron, a French mathematician, was struck by Krige’s empirical work. In 1962 he formalized the mathematical theory behind Krige’s observations, creating what we now know as kriging. The kriging revolution: Unbiased estimates with minimal variance Quantification of uncertainty through the kriging variance A rigorous statistical method replacing specialists’ “gut feeling” A mathematical foundation based on variograms and spatial correlation Transformational impact: Kriging was not merely an incremental improvement-it was a paradigm shift. For the first time in the history of mining, there was a method that not only estimated grades but also quantified the confidence placed in those estimates. 🔹 Concurrently, another revolution: In 1965, Helmut Lerchs and Ingo Grossmann solved another fundamental problem: what is the optimal pit? Their algorithm, based on graph theory, provided for the first time a mathematically optimal solution for delineating open pits. Before: manual pit design based on experience. After: mathematical optimization ensuring maximum economic value. The perfect marriage: Kriging provided reliable grade estimates. The Lerchs–Grossmann algorithm optimized economic recovery. Result: scientific planning in place of intuition. A historical note: the Lerchs–Grossmann algorithm only became widespread twenty years later, once computers were powerful enough. The Whittle 3D software of the 1980s was the milestone that democratized pit optimization. Why does this matter today? These two pillars-reliable estimation and mathematical optimization-laid the foundation of modern mining. Without them, we would not have the basis to integrate machine learning, stochastic simulation and advanced optimization, as we see today. The journey continues: 1960s: Kriging + Lerchs–Grossmann 1980s: Stochastic simulation 2000s: Optimization under uncertainty 2020s: Machine learning + geostatistics From South Africa to the world, from intuition to science, from deterministic to probabilistic methods.

La dilution minière est l'un des facteurs les plus importants affectant l'économie des projets miniers. Bien que nous fassions de notre mieux pour identifier et calculer tous les autres éléments de coût d'un projet, aussi petits soient-ils, il est courant de formuler des hypothèses générales sur la dilution au lieu de la quantifier. Cela est généralement dû à un budget insuffisant, à du temps pour les études et également à l'absence d'une méthodologie bien définie pouvant être utilisée. Au lieu de quantifier la dilution dans les études minières, il est courant de supposer une dilution générale telle que 5% pour les gisements massifs et 10% pour les gisements de forme tabulaire. Bien que ces chiffres puissent être un bon point de départ dans les premières étapes des études minières, ils ne prennent pas en considération la complexité du problème.

🫵 The plot Conservative practices contribute to substantial economic inefficiencies in the mining sector. Industry-wide impairment losses exceeded $120 billion during the 2013/14 commodity downturn, with resource and reserve estimation issues identified as contributing factors in 17% of feasibility study failures. McKinsey estimates $100 billion in potential value optimization across mining feasibility studies, with resource classification standards identified as one element requiring improved rigor. 🫵 The dirty little secret Ore deposit valuation hinges on robust reserve estimation, yet prevailing mining standards conflate geological confidence with grade uncertainty, leading to conservative biases and undervaluation. Geostatisticians often downgrade resources by focusing on local grade variability, ignoring geological reliability established in Indicated Resource classifications resulting in reduced reserves, deterring investment despite solid deposit foundations. The evaluation and valuation of ore deposits too often undermined by the conflation of geological confidence with grade uncertainty. 🫵 The gatekeepers labyrinth The classification of mineral resources and reserves has long struggled with this in both resource management and deposit valuation. Current practices, under the CRIRSCO umbrella, geostatisticians override established geological assurances based solely on grade variability, resulting in unnecessary reductions in reported ore reserves. Decoupling these risks and employing statistical confidence intervals, mining can preserve reserve estimates, capture upside potential, and enhance valuation accuracy. 🫵 Clear precedent The petroleum industry's Proven-Probable-Possible framework (PRMS), assigns explicit confidence intervals to reserve estimates without abandoning sound geological interpretations. The framework addresses both mineral resource classification requirements and deposit valuation imperatives, recognizing that classification decisions directly influence market valuations, access to capital, and investment returns. Such an approach recognizes that resource classification decisions directly impact deposit valuations, making the conversion of Mineral Resources Reserves relevant to the valuation of Mineral deposits. Ignoring this risk conflation attracts opportunity costs and consequential economic harm to investors because undervaluation of projects of well-understood deposits that receive inappropriate classification due to statistical limitations rather than geological uncertainty can be significant. Downgrading resource categories invokes different valuation multiples in market assessments resulting in poor market valuations that impede access to capital and capital formation. The misallocation of Mineral Resources can trigger the requirement for severe impairments charges that qualified persons seem aloof to.

Resource estimation is a crucial process in the mining industry, serving as the foundation for mine planning, design, and economic evaluation. It involves analyzing geological data to determine the quantity and quality of mineral resources present within a deposit. The process typically begins with geological modeling, followed by geostatistical analysis using techniques such as kriging, inverse distance weighting, and simulation methods. These tools allow geologists to predict grade distribution and spatial variability within the ore body. Accurate resource estimation reduces uncertainty, improves investment confidence, and ensures that extraction remains both technically feasible and economically viable. With the advent of machine learning and 3D modeling software, modern estimations are becoming more precise and dynamic. Ultimately, resource estimation bridges science and strategy turning geological observations into actionable insights that guide sustainable mineral development.

The Radial Basis Function (RBF) interpolation method has emerged as a powerful geostatistical tool for mineral resource estimation, offering flexibility and robustness in modeling complex orebody geometries and grade distributions. Unlike traditional estimation techniques such as Inverse Distance Weighting (IDW) or Ordinary Kriging, RBF utilizes a smooth mathematical function that fits through known data points while minimizing interpolation error. This property enables the method to capture both global and local grade variability with high precision. In this study, the RBF approach was applied to a gold deposit using drillhole assay data to generate a continuous three-dimensional grade model. Various kernel functions—such as multiquadric, Gaussian, and thin-plate spline—were tested to optimize model accuracy and performance. Cross-validation results demonstrated that the RBF model effectively reproduced spatial grade trends and provided smoother, geologically realistic surfaces compared to conventional methods. The resulting block model was validated against composited data and geological interpretations, showing strong correlation and reduced estimation bias. The RBF method proves particularly advantageous in deposits with irregular sampling patterns or non-stationary grade distributions. Consequently, RBF interpolation represents a valuable alternative for modern resource estimation workflows, especially when integrated within advanced 3D geological modeling software such as Leapfrog Geo.

Le swath plot ci-joint offre une validation clé de notre modèle de ressources pour le gisement aurifère. Points Clés : Cohérence des Estimations : Les méthodes d'estimation par Inverse Distance (ID) et Kriging (Kr) montrent des tendances de teneur remarquablement similaires (lignes magenta et olive). Cette concordance renforce la fiabilité de notre modèle de blocs. Corrélation Teneur-Volume : Une forte corrélation est observée entre les zones à haut volume de minerai (barres beiges) et les pics de teneurs moyennes. La zone principale du gisement (Swaths 60-90) est clairement identifiée comme la plus riche et la plus volumineuse. Distribution de la Minéralisation : Le gisement présente une minéralisation principale concentrée, avec des variations de teneur bien capturées par le modèle sur l'axe X. Ces résultats confirment que notre modèle de blocs représente fidèlement la distribution des teneurs, un atout essentiel pour la planification minière et l'optimisation de l'extraction. #GéologieMinière #EstimationDeRessources #ValidationDeModèle #ExplorationMinérale #Or