JORC Code Research Articles

Ni-Co Bearing Laterites from Halmahera Island (Indonesia)

Eastern Indonesia, including the island of Halmahera, is a region with a high mineral potential, particularly Ni-Co, Au-Cu, and Ag ores, which are a globally important and critical source of raw materials (CRMs). The research was conducted within the framework of scientific cooperation between the Faculty of Geology, University of Warsaw (Poland), and PT Halmahera Resources Percasa Ltd. (Jakarta, Indonesia) Between the years of 2009 and 2011, 42 boreholes were drilled using an impact system (up to 15 m below surface) and 3 test pits (up to 8 m below surface). The presence of a laterite deposit containing Ni-Co mineralization was identified on the license area. The resources estimated in accordance with JORC Code, with a cut-off grade Ni ≥ 0.5%, equaling 185,510 t Ni and 17,747 t Co, with the stock of raw material amounting to 14.8 million t and with an average content of 1.00% Ni and 0.13% Co. The ore in the deposit has mixed character. To date, studies have shown the dominance of oxide ore, but saprolite composed of magnesium silicates was also identified in significant amount. The Ni mineralization in oxide ore (limonite) is bound to goethite and manganese minerals, while in the case of silicate (saprolite) ore, it occurs locally in the form of veins as well as zonally in the weathered serpentinites. Cobalt mineralization is almost entirely related to the Mn minerals that occur in the lower oxide zone. It has been found that both serpentinites and harzburgites (and possibly locally lherzolite) are the parent rocks for laterite deposit.

New Challenges to the Deep Development of the Bulqiza Chrome Mines

Abstract Bulqiza chrome mine is one of the most important chromium mines and mining activities in Albania. It is the deepest mine in the Balkans and possibly even in Europe. Recently, the inner shaft of the mine reached a depth of 1000 m, measured from the surface, or −180 m below sea level. Like all deep metal mines, this mine also faces a different set of challenges during its development. The first and most important challenge is that of improving the degree of geological research and knowledge of this mine and assessment of geological resources and reserves according to JORC Code 2012 edition. In addition, a series of other challenges related to increasing the depth of the mine represent the object of this paper: rock and ore stability and the underground voids support; improvement of mining methods and technologies; groundwater and its pumping; temperature, air parameters and mine ventilation. Among other things, these problems were solved using various computation and simulation programs.

Justification of the CRIRSCO standards and JORC Code for mineral resources and reserves in high-mountain regions

The article discusses the CRIRSCO and JORC international reporting standards for the transition to the JORC Code in evaluation of mineral resources in the Kyrgyz Republic.

Polish approach to the mineral deposits safeguarding. Experience and problems

The basis for reasonable mineral policy aiming the safeguarding of mineral deposits is the knowledge of their demonstrated resources or potential occurrences, and their location. Such knowledge is based on exploration results, existing or planned land use and environmental protection requirements. In Poland, since 1953, exists the standardized mode of mineral resources reporting. It is a system comparable to the JORC Code exigencies and UNFC standard. The areas of occurrence of demonstrated, as well as prospective mineral deposits, are presented on geo-environmental maps 1:50,000, that cover the entire country. They allow to visualize possible conflicts with the areas of protected environment, fertile soils, forests as well as existing housing developments. The degree of such conflict is evaluated using a ranking procedure and, later, presented on additional special maps. The valorization of deposits according to their importance on a national, regional or local scale, and accessibility for mining, allows for indicating the most valuable ones, and select these of public importance (MDoPI - Mineral Deposits of Public Importance) at national and local level.

Defining Uncertainty: Comparing Resource/Reserve Classification Systems for Coal and Coal Seam Gas

Transparent, objective, and repeatable resource assessments should be the goal of companies, investors, and regulators. Different types of resources, however, may require different approaches for their quantification. In particular, coal can be treated both as a solid resource (and thus be mined) as well as a reservoir for gas (which is extracted). In coal mining, investment decisions are made based on a high level of data and establishment of seam continuity and character. The Australasian Code for Reporting of Exploration Results, Mineral Resources and Ore Reserves (the JORC Code) allows deposits to be characterised based on the level of geological and commercial certainty. Similarly, the guidelines of the Petroleum Resource Management System (PRMS) can be applied to coal seam gas (CSG) deposits to define the uncertainty and chance of commercialisation. Although coal and CSG represent two very different states of resources (i.e., solid vs. gaseous), their categorisation in the JORC Code and PRMS is remarkably similar at a high level. Both classifications have two major divisions: resource vs. reserve. Generally, in either system, resources are considered to have potential for eventual commercial production, but this has not yet been confirmed. Reserves in either system are considered commercial, but uncertainty is still denoted through different subdivisions. Other classification systems that can be applied to CSG also exist, for example the Canadian Oil and Gas Evaluation Handbook (COGEH) and the Chinese Standard (DZ/T 0216-2020) and both have similar high-level divisions to the JORC Code and PRMS. A hypothetical case study of a single area using the JORC Code to classify the coal and PRMS for the gas showed that the two methodologies will have overlapping, though not necessarily aligned, resource and reserve categories.

Uncertainty assessment of spatial domain models in early stage mining projects – A review

• Performance of feasibility studies in mining projects is poor which could be due to omission of quantitative uncertainty assessments in public reporting. • JORC 2012 standards require quantitative uncertainty assessment for geological and spatial domain models. • Current methodologies of quantitative uncertainty assessment and communication exist and can be used in early-stage mining projects. • Professional development and incorporating software and process workflows could be the way to go to improve current reporting practice. Sustainability of mining projects is linked to informed investment decisions based on public reporting of exploration and mineral resource estimation results. In Australia, guidelines for public reporting are established by the Joint Ore Reserves Committee reporting code through the JORC Code (2012). Although assessment of uncertainty in the results reported is a requirement, this is often communicated in a qualitative manner and subjectively evaluated. This can become a liability if not communicated effectively, particularly in early stages of mining projects when spatial domains of geological interpretation and mineralization envelopes influence reliability of resource estimates. This review describes methodologies for quantitative uncertainty assessment and communication, and explores how they could be applied in public reporting practice. The complexity, cost and additional work of doing a quantitative assessment could hinder a straightforward implementation. This could be overcome if mining companies budget for quantitative uncertainty assessment and associated professional development. A compulsory requirement for inclusion of uncertainty assessments in public reporting or use of standardized subjective language would improve industry practice.

Research on Reserve Classification of Solid Mineral Resources in China and Western Countries

Combined with the development and application of mining markets at home and abroad, the following understandings are obtained through comparative analysis of GB/T 17766-1999 Classification for resources/reserves of solid fuels and mineral commodities, GB/T 17766-2020 Classification for resources/reserves of solid fuels and mineral commodities and JORC Code. 1) GB/T 17766-2020 is more concise and efficient, focusing on the objective evaluation of economic value; 2) Since the form and connotation of GB/T 17766-2020 is similar to JORC Code and other Western norms, the implementation of GB/T 17766-2020 will be conducive to international integration; 3) A variety of factors caused the low recognition of domestic reports and small market influence. However, according to GB/T 17766-2020, we can gradually improve the recognition and influence by means of strengthening process management and responsibility to natural persons.

Independently Certified Industry‐specific Disclosures to the Capital Market: The JORC Code in the Australian Mining Industry

We investigate compliance with the Australian JORC Code for reporting mineral resources and ore reserves, the quality of the disclosure, and its impact on the capital market. The compliance and quality assessment is conducted by two experienced geologists who find that while the overall reporting quality improved after the 2012 revisions to the Code, they disagree on the extent of improvement. This reflects the uncertainties involved and the difficulty in interpreting the reports. Both geologists agree that the greatest improvement is seen in early‐stage projects, consistent with the expectation that there are more uncertainties surrounding these, and the additional information disclosed under the 2012 JORC Code appears to assist in reducing the uncertainties to some extent. The capital markets study shows that JORC announcements have a significant impact on investors’ assessments of firm value, and that the announcement impact is higher after the 2012 revisions designed to strengthen the disclosure requirements. This is consistent with post‐2012 JORC reports conveying higher information content. There continues to be information leakage prior to announcement date. Further tests show a widening of bid–ask spreads in the post‐2012 period, suggestive of higher information asymmetry. While the probability of informed trading declines for large firms, it remains statistically unchanged for the rest of the sample. The findings reiterate the need for regulators and standard setters to be cognisant of unintended consequences of their decisions. The substantiation process under JORC involves a delay in the release of ‘news’, a ‘chilling’ effect with larger announcement effects.

Understanding Geology and Structure: An Essential Part of Mineral Resource Estimation

The assumption of continuity of mineralisation between sampling points, as stated in the JORC Code, requires a “confident interpretation of the geological framework”. The elements of relevance to a geological framework vary greatly depending on th e commodity and style of mineralisation. In general terms, at least two elements must be considered to underpin a geological framework: space and time.The geometry and location of a mineralised body are controlled by physical and/or chemical elements, which can be unravelled by detailed geological mapping, adequate geochemical (including a quality analysis-quality control program) and structural interpretations, and by 3D geological modelling. These elements may involve, among other, aspects of stratigraphy, chemical or physical properties of the rocks (e.g. texture, grain size) and structural features such as faults, fractures and folds.Mineralisation events that lead to economic deposits are often relatively short-lived periods of focused fluid transfer and element-exchange, which result in mobilisation and deposition of metals in well-defined areas. Understanding the temporal framework and interaction of structural elements and mineralising events (determining genetic relationships, e.g. pre-, syn- and post-mineralisation) results in the development of more accurate geological models and can lead to predictive capabilities and new discoveries.We present case studies in regional metamorphic, igneous, sedimentary and surficial geological environments, demonstrating how understanding the mineralisation system not only results in increased confidence in the resource, but also facilitates reduction of exploration risks.

High-Grade Silica Sands in The Eastern Murray Basin NSW

Investigations in 1979 defined a sand resource at Wah Wah with three potential processing options to yield sand suitable for colourless glass making. In December 2016, further drilling was completed to infill some of the previously drilled area and extend into new areas. From this drilling, coloured and white sand resources have been defined, overlain by a clay unit. The sand has generally been considered to have a fluvial origin, but recent work suggests that the white sands may have a beach origin. White sand is defined by the 0.050% Fe2O3 contour and this resource coincides generally with higher yield, mostly underlying 6m to 8m of clay - the thinner overburden area. Estimated resources are 15 million tonnes of white sand with 0.035% Fe2O3 and 0.20% Al2O3 at a yield of 58% for 8.7 million tonnes of sand suitable for colourless glass making. Sand not suited to glass making can be used for other products. These resources are Indicated Resources for reporting under the JORC Code 2012. They are defined by drilling and testing, and found to be suited for glass and other uses. From the investigations, a number of processing techniques can be employed with the final decision dependant on user requirements. However, the 2016 work demonstrated that an attrition-gravity process will be suitable for colourless glass sand, and cheaper than the other options considered in 1979. Based on results, the sand appears to be suitable for other products, including filter media, various construction uses, and other applications depending on markets. Compared to the resource defined in 1979 this deposit is now expected to be suited to: - Selective extraction, - Reduced focus on a single market, - By-products to increase overall yield, - Lower cost processing for the higher value products, - Certainty that there is sufficient resource to meet longer term needs for a range of products.

National reporting codes for the mineral industry: The case of JORC in Australia.

A revised version of the Australasian Code for Reporting of Exploration Results, Mineral Resources and Ore Reserves commonly called the JORC Code was released in Australia in December 2012. This paper provides a summary of the principles that guide the Code, and the definitions therein, as well as the rationality behind adopting the Code as a Public Reporting tool. Brief examples of reporting requirements are also discussed. Additionally, references and a general comparison to the Pan-European Reserves & Resources Reporting Code (PERC standard) are presented. Although, in Greece there is no relevant Regulatory Framework in place yet or enforcement of any International Code, the adaptation of PERC is probably ahead, and hence this paper aims to open the discussion among geoscientists and mining engineers for the opportunities and the challenges that they will face.

Geostatistical support for categorization of metal ore resources in Poland

Abstract The authors attempted to introduce some components of the Australasian JORC Code system to the categorization of Polish Cu-Ag and Zn-Pb ore resources. The proposed geostatistical method of resource categorization applies two criteria: continuity of deposit parameters described by semivariograms and permissible, relative standard error of resources estimation determined with the ordinary kriging procedure. Considering the first criterion, we propose the following values of autocorrelation coefficients, which define the ranges (distances) of the resources categories around the measurement sites (e.g., exploration wells): “measured” category (A + B in the Polish system) – the values of the autocorrelation coefficient from 1 to 2/3, “indicated” category (C1 in the Polish system) – the values of the autocorrelation coefficient from 2/3 to 1/3, “inferred” category (partly C2 in the Polish system) – the values of the autocorrelation coefficient from 1/3 to 1/20, “out-of-doors” category (partly D in the Polish system) – the values of autocorrelation coefficient from 1/20 to 0. The second criterion of resources categorization is based upon the relative, standard errors of resources estimations calculated for the parts of deposit defined with the first criterion. The following permissible values of errors determined as the errors of ordinary kriging have been proposed: “measured” category (A + B in the Polish system) – 10% error, “indicated” category (C1 in the Polish system) – 20% error, “inferred” category (partly C2 in the Polish system) – 30% error, “out-of-doors” category (partly D in the Polish system) – 50% error. It was found that the Polish metal ore deposits reveal low continuity of deposit parameters, as indicated by a high share of nugget variance in the overall variability of these parameters. Moreover, an inconsistency was observed between the semivariograms of deposit parameters based upon samplings of drill cores and underground mine workings, which results in extreme differences in the ranges of resources categories around the sampling sites. This, in turn, causes radical discrepancies in estimated resources. Thus, it was concluded that the sufficiently credible categorization of resources is only possible when a significant part of the deposit is explored with mine workings, in which the grid of sampling sites is much denser than that of exploration wells. It was proposed that the principal criterion of resources categorization should be the permissible error of estimations whereas the continuity of deposit parameters should only be a supplementary criterion.

Geology and metallogeny of Jordanian uranium deposits

Uranium mineralisation has been known within the Hashemite Kingdom of Jordan for a long time and in 2014 maiden mineral resources were estimated for the Central Jordan Uranium Project (CJUP) following the reporting principles of the JORC Code (). Based on this estimate the CJUP contains 269 mt of mineralisation at an average grade of 135 ppm U3O8 (36·4 kt of contains U3O8) within an Inferred Resource. The objective of this paper is to describe the geology and the metallogeny of uranium mineralisation in Jordan, providing new insights into this mineralisation that remains largely unknown outside of the country. Most of Jordan's territory is covered by platform sedimentary rocks that generally formed during the Cretaceous and Paleogene. The majority of uranium mineralisation is confined to Upper Cretaceous sediments, in particular the Al Hisa Phosphorite (AHP) and the Muwaqqar Chalk Marl (MCM) formations. The MCM formation hosts surficial type-mineralisation that is mainly concentrated in a narrow, approximately 4·5 m thick layer that is distributed close to the topographic surface and is independent of phosphorite beds. This mineralisation, termed ‘surficial’, is the economically most important type of uranium in Jordan and currently represents the main exploration target in this area. The main uranium minerals within the surficial layer are uranium vanadates, colloquially referred as carnotite group minerals. The average uranium grade rapidly decreases below a depth of 4–5 m, although mineralisation continues to depths of 30–40 m. Beneath the surficial layer, uranium mineralisation is distributed as lenses that are generally small and discontinuous. This mineralisation, termed ‘Deep’, has many common features with the surficial mineralisation, including similar mineralogy and chemical composition and may represent a transition between surficial and phosphorite-hosted types. The metallogeny of surficial uranium mineralisation is well studied, although several important questions remains unanswered. In particular, close spatial relationships between pyrometamorphic marbles and the uranium mineralisation can be observed on regional geological maps and in the field. Two different models have been proposed to explain the formation of the pyrometamorphic marbles in central Jordan, namely the burning of bituminous marls and an alternative model involving the combustion of deep reservoirs of hydrocarbon gases relating to mud volcanoes. Tectonic faults have also possibly played a role in the distribution of uranium mineralisation in central Jordan. This is in particular relevant for the Khan Azabib area where higher grade mineralisation and their associated gamma anomalies are broadly coincident with regional faults. These faults may have acted as permeable zones, facilitating migration of the hyperalkaline solutions that leached uranium from the host rocks. Eventually, the liberated uranium was redistributed by supergene processes towards the surface, where uranium minerals precipitated along the contact between saprolite and fresh to weakly weathered rocks. In summary, the uranium deposits of Central Jordan resulted from the interplay of sedimentary, tectonic, and metamorphic events, with the final impact made by climatic factors and chemical weathering processes. The AHP formation hosts phosphorite-hosted type mineralisation that formed as a result of the synsedimentary concentration of uranium in apatite and is abundant in the Hasa–Qatrana area of central Jordan. The surficial parts of the phosphorite-hosted uranium mineralisation have also been partially modified by weathering, which has released uranium from apatite and redistributed and precipitated it as ‘carnotite’. This type of mineralisation is present at the Sahb El Abyad prospect located in the south-eastern part of Jordan. Uranium mineralisation also occurs in hydrothermal veins that cross-cut Cambrian rocks exposed along the plate margin in the Dead Sea rift valley. This mineralisation type is different to the mineralisation within the central Jordanian deposits and it is rare in Jordan, so far being found only in the Dana area.

Wykazywanie zasobów wêgla kamiennego w Polsce zgodnie z JORC Code / Reporting of Hard Coal Reserves and Resources in Poland on the Basis of the JORC Code

Streszczenie Wykazywanie zasobów złóż kopalin oraz podawanie tych informacji do wiedzy publicznej stanowi istotne zagadnienie w odniesieniu do zasadności prowadzenia działalności gospodarczej w branży geologiczno-górniczej. Od szeregu lat w przestrzeni międzynarodowej funkcjonuje system raportowania i klasyfikacji zasobów kopalin stałych bazujący na australijskim kodeksie JORC. Dokument ten, honorowany przez giełdy, przedstawia minimum standardów i wytyczne niezbędne do rzetelnego i wiarygodnego wykazywania zasobów złóż; kodeks JORC stosuje dwie podstawo­we kategorie zasobów: resources i resenres, z których pierwsza odnosi się do zapasów (zasobów bilansowych) kopaliny, a druga do zasobów wydobywalnych - czyli wielkości możliwych do wy­dobycia przy uwzględnieniu aktualnie dostępnych środków technicznych i obecnych kryteriów ekonomicznych. Układ klasyfikacji jest hierarchiczny - zasoby resen/es stanowią podzbiór zapasów. Wraz z napływem informacji geologicznej wśród tych ostatnich wyróżnia się zasoby domniemane (inferred), oznaczone (indicated) oraz zmierzone (measured), natomiast w obrębie pierwszych - zasoby prawdopodobne (probable) i pewne (proved). Zasoby bilansowe zmierzone oraz wy doby walne pewne stanowią najlepiej rozpoznane partie złóż. W związku z sukcesem JORC wiele krajów wprowadziło bazujące na nim własne, narodowe kodeksy wykazywania zasobów. Kodeksy te sku­pione są w obrębie CRIRSCO - Komitecie Międzynarodowych Standardów Wykazywania Zasobów Kopalin [stałych]. Polska klasyfikacja zasobów ma hierarchiczny charakter - z łącznych zasobów geologicznych wyodrębnia się zasoby bilansowe obejmujące zasoby przemysłowe i nieprzemysłowe. W zależności od zakresu wiedzy geologicznej zasoby wykazuje się w pięciu kategoriach rozpoznania: D, C2, Cj, B i A. Po odjęciu strat i uwzględnieniu zubożenia otrzymuje się zasoby eksploatacyjne. Jak do­tychczas, pomimo doświadczeń rosyjskich w tym zakresie, w Polsce nie wypracowano standardu harmonizującego system polski i międzynarodowy. Treść niniejszego artykułu przedstawia pro­pozycję takiego dostosowania.

Ordinary kriging for the estimation of vein type copper deposit: A case study of the Chelkureh, Iran

Estimation of mineral resources and reserves with low values of error is essential in mineral exploration. The aim of this study is to estimate and model a vein type copper deposit using ordinary kriging method. After studying of variograms in different directions it was found out that the ore deposit has no anisotropy. The best fitted variogram model was considered for ordinary kriging estimation. Cross-validation was used to evaluate the accuracy of the variogram model for kriging. After trial and error a variogram with the best summary statistics was chosen. Model consists of a pure nugget effect with 0,30 amplitude plus a spherical scheme with sill 1.10 and range 30 m. The cross validation results showed that the correlation coefficient between estimated and real data was 0.829. The resource was classified based on calculated estimation errors by JORC code. Results showed that ordinary kriging can be used to model and estimate the vein type deposit. Consequently a three dimensional model of estimated value and error estimated value was provided by ordinary kriging to divide the ore into an economic and uneconomic part.

Taxation of Mineral Products in Russian Federation

The Code of Joint Ore Resources Committee (the JORC Code) is widely adopted be mining industry for the compiling of mineral resources and reserves reporting. The results of information transfer from one system to another will depend on the nature of deposit and complexness of its geological construction of mineral extraction tax base. The basis for placing the resources on the State Balance Sheet in Russian Federation are the opinion letters of the state expert appraisal bodies, according to which, the licenses are granted to the users of subsurface resources. For the purpose of taxation, the chapter 26 of the Tax Code of Russian Federation accepted the “multicomponent complex ores”. However, this term is interpreted in different ways, which complicates the definition of the taxation objects. The author of this article proposed to state the whole list of minerals, in the production license. It is proposed to exclude the “multicomponent complex ores” term from the chapter 26 of the Tax Code of Russian Federation, for the purpose of non-admission of interpretation of this term in different ways. While processing mineral raw material we have basic product and by-products and wastes products. The sale proceeds are 3% from the accounting basic production. If the sale proceeds from realization of the by-product is more than 3%, this product is basic. This criterion is developed for taxation. The use of recycled resources is aimed at reducing of environmental risks. It is important for economic and environmental stability of country. Methods for determination of tax rates on mining (exampled at the estimation of raw materials’ cost and indirect estimation method for determining the amount of minerals and the price factor) are considered in this article.

Does Industry Specialist Assurance of Non-Financial Information Matter to Investors?

SUMMARYPrevious studies in the financial economics literature highlight the value of non-financial information in Internet and telephony stocks (Amir and Lev 1996; Trueman, Wong, and Zhang 2001). Other studies consider the financial and share price performance implications of assurance of non-financial information such as ISO 9000 certification (Corbett, Montes-Sancho, and Kirsch 2005), Total Quality Management awards (Hendricks and Singhal 1997), and non-financial information disclosure (Coram, Monroe, and Woodliff 2009). However, prior studies have occurred in settings where disclosure and assurance of non-financial information is voluntary. We provide evidence on the value of assurance of non-financial information where the assurance of public resource disclosures made under the JORC Code by Australian Mining Development Stage Entities are mandatory. The assurance role undertaken by Competent Persons reporting under the JORC Code bears many close similarities to the financial reporting assurance role undertaken by auditors. Further, the information environment of MDSEs is characterized by high information asymmetry and the reality that the utility of non-financial technical information supersedes financial statement information in firm valuation. We document very weak evidence of greater abnormal returns evident when reserve disclosures are provided by specialist mining consultants. In supplementary analysis, we test for implications of switching mineral consultant and find that clients experience significant positive abnormal returns when the successor is larger. Overall, our findings support the insurance hypothesis, in that mandatory specialist assurance matters little where litigation risk is low.

Mineral resource estimation of the Brockman 4 iron ore deposit in the Pilbara region

Brockman 4 is a large iron ore deposit hosted by the Brockman Iron Formation in the Pilbara region and is mined by Rio Tinto Iron Ore. Drilling is mainly by the reverse circulation method and samples are taken at 2 m intervals using a rotary cone splitter or historically by riffle splitter. Samples are geologically logged, assayed by X-ray fluorescence for iron, silica, alumina, phosphorus, manganese, sulphur, titanium oxide, calcium oxide, magnesium oxide, and 19 other trace elements; and measured for loss on ignition by thermogravimetric analysis. Mineralisation is estimated by ordinary kriging with unfolding and waste by inverse distance interpolation. The model is validated, reconciled with historic production, classified according to the 2012 Edition of the JORC code and stored in a SQL Server database.

A new approach for the geological risk evaluation of coal resources through a geostatistical simulation

Estimations of mineral resources and ore reserves have been recently widely used by mining engineers and investors. The classification framework based on the prepared code by the Joint Ore Reserves Committee of The Australasian Institute of Mining and Metallurgy, Australian Institute of Geoscientists and Minerals Council of Australia (JORC code), which is one of the international standards for mineral resource and ore reserve reporting, provides a template system that conforms to international society requirements. Recent research has shown that an existing fault risk can affect the mineral resource and ore reserve estimation. According to this research, the faulted area that is involved in the effect on the estimated region is so extensive that it is not distinguishable. In this research, a new method called FGT (F for fault, G for grade and T for thickness) is introduced and presented for the estimation of mineral resources. The proposed method can provide an error map of a particular aspect of the combination of coal accumulation (G), fault risk (F) and thickness (T), and its output would categorise the mineral resources. This method was implemented in the Parvadeh Ш coal deposit, which is located in the eastern portion of Central Iran. The deposit contains five seams named B1, B2, C1, C2 and D; of these, C1 was selected as the most important seam in the exploratory grid analysis. Thus, C1 alone can reflect the properties of the Parvadeh Ш deposit. In this study, we compared the conventional method and the FGT method. This comparison indicated that the areas that should be rejected from the region in the FGT method are less and more distinguishable than those determined with the conventional method. Therefore, the inferred resources can be completely differentiated from the indicated and measured resources with a high resolution. The conventional method cannot distinguish between these three categories at this level of resolution. Therefore, the FGT approach has high precision in classifying the coal resource compared to the conventional method.

Author's Reply to "Comments on Classification and Reporting of Mineral Resources for High-Nugget Effect Gold Vein Deposits," by M. Vallee

There are two main issues stemming from Vallee’s (2002) comments on Dominy et al. (2001b). First, he raises the importance of quality assurance/quality control (QA/QC) during resource estimation programs, and second, he indicates that the resolution and understanding of continuity (grade and geological) issues are paramount in the classification of resources. In particular, continuity is critical at the boundary between the Inferred and Indicated Mineral Resource categories. The original contribution agrees with the importance of these points, and the principal author offers the following discussion and clarification. Further comment is also provided on the reporting of grade uncertainty through grade ranges. It is worth remembering that vein-gold deposits (e.g., shear-zone, lode-gold, mesothermal types etc.), particularly those containing coarse gold particles (e.g., >100 μm), generally show large variations in grade and an erratic grade distribution. In most cases, diamond drilling is a good measure of geological continuity (depending on drill spacing), but a poor measure of grade and its distribution. High-nugget effect deposits rank among the most difficult deposit types in terms of producing an accurate and precise resource estimate, and clearly represent a distinct deposit type. ### Quality Assurance/Quality Control The issue of quality assurance (QA) and quality control (QC) during exploration, estimation/evaluation and exploitation has been at the forefront of industry perceptions since the Bre-X affair in the late 1990s. The need for QA/QC programs is paramount in any mining/minerals project (Vallee, 1998a, 1998b, 2002). Quality is a critical issue at all stages of a minerals project. For example, QA/QC of analytical and test data, and the corroboration of geological data within the resource/reserve estimation process must now be considered mandatory. Indeed, the Canadian National Instrument 43–101 requires mandatory QA/QC programs (CSA, 2001). The 1999 JORC Code does not prescribe QA/QC programs but, for example, QA/QC for sampling/assaying is …