Mineral Resource Estimation

Issue: 
#51
3D mineral resource modelling at the Balya underground mine in Turkey
In this dynamic and challenging time for the mining industry, SRK Consulting’s mineral resource consultants continue to stay up to date. Using the latest technological advances and considering regulatory developments, we can help our clients derive the most value from their mining assets. Challenging market conditions have led to increased...
The CIS countries inherited the resource estimate code from the Soviet era that was originally created and is still updated by the Geological Commission for Reserves or GKZ. The official method of the resource estimation is still based on sections and plans. Now the GKZ body in Russia plans to...
High grade drill intersects are often a welcome occurrence for a mining company, its shareholders and/or potential investors. They represent the potential for even greater metal content in the deposit. However, from a resource evaluation perspective, they may present complications in generating a realistic resource estimate, by overestimating or underestimating...
Kvanefjeld is the flagship orebody of Greenland Minerals and Energy Ltd’s (GMEL) Northern Ilimaussaq project. Kvanefjeld contains the world’s largest mineral resource of rare earth elements, as defined by the reporting standards of the JORC Code or NI 43-101. In 2011, SRK Australia prepared a Mineral Resource estimation for the...
Update on geostatistical advances
Most recent developments in resource estimation have taken place in the following fields: Geological modelling: 3D modelling has become much faster and more accurate, by implementing fast interpolation algorithms within specialised software like Leapfrog, GOCAD, Geomodeller. More traditional mining packages have added implicit modelling to their capabilities (Minesight, Micromine, etc.)...
The Committee for Mineral Reserve International Reporting Standards (CRIRSCO) has consolidated reporting codes and standards to produce a consistent definition of a Mineral Resource. “A ‘Mineral Resource’ is a concentration or occurrence of material of economic interest in or on the Earth’s crust in such form, quality and quantity that...
Coal mining in Mozambique
Classifying coal deposits in recently explored basins to internationally recognised reporting codes requires close attention to data quality and a comprehensive understanding of the geology. The coal basins and sub-basins of the Zambezi coalfield are structurally complex, affected in varying degrees by intrusive bodies, with centimetre scale inter-bedded coal and...
General workflow for a mineral resource estimate
At some point during your professional career as a Resource Geologist, you can expect that the Mineral Resource estimates (MRE’s) you have produced in accordance with international reporting codes will be subject to a technical audit by an external organisation, most likely by a Competent/Qualified Person from a third-party consultancy...
CRIRSCO template
In early 2015, India introduced a set of new mining rules, using the terminologies defined in the UNFC 1997 guideline and the CRIRSCO Template. Since then, mapping the Indian Resource Classification system against the CRIRSCO Template has become extremely important to the Indian and foreign investors. In the recent past,...
Generally speaking, grade interpolation can be validated by VMS (visual assessment, mean assessment, swath plot validation) and block variance validation. These methods are easily understood and applied, except for the block variance validation. When applying kriging to grade interpolation, the theoretical block variance adjustment ratio (f) and the actual block...
Estimating metallurgical variability: a case study
After discovering a mineral deposit, delineating the drilling, and developing a geological framework, the next step is usually estimating metal content by quantifying the grade and tonnage of the mineral occurrence. To support mine design and the economic analysis of the project, a geometallurgical model can also be generated by...
Scatter plots of optimal kriging against grade control and a single simulation against grade control. Note the distributions with respect to the misclassification quadrants and the increased dispersion of the simulated values.
A fundamental concept of geostatistics that is often overlooked or misunderstood in resource estimation during the early project stage is the relationship between the global grade tonnage curve and the quality of the local block by block estimate. Kriging, with a properly optimised set of search parameters, will always give...
Estimating Bulk Density
Mineral resources are reported in tonnage and grades. While great care is placed on generating a reliable estimate of grade, determining bulk density for resource estimation is often overlooked. Instead, a simple average value of bulk density is used. While this estimate can work for some deposit types, an overly...
Linear Estimators, such as Ordinary Kriging, can produce smoothed assessments in the results of your resource estimation. The conventional Uniform Conditioning method estimates a tonnage and grade of mineralisation that can be recovered using the Selective Mining Unit (SMU) of size at the chosen cut–off value. A set of grade...
Grade domains are often considered, following the modelling of geologic domains, to further control the distribution of grades during resource estimation. This is usually achieved by wireframe modelling on sections displaying grade assays or composites, indicator kriging, and/or implicit modelling using radial basis functions. The latter approach is often facilitated...
Historically the modelling of narrow vein deposits has relied on classical two dimensional methods to estimate tonnage, grade and thickness in narrow vein deposits. The use of three dimensional models has been limited by complexity of this style of mineralisation leading to difficulties generating valid wireframes, associated with linking issues...
Despite the intention to include geological controls during the wireframing phase of the mineral resource estimation process, modelling methodology is sometimes reduced to connecting grade data along trends judged to be geologically valid. This is specifically the case for precious metal vein deposits where the grade distribution is controlled by...
Implicit Software Modelling technologies are designed to improve 3D geological modelling for exploration and resource definition. Since 2005 when SRK consultants in Australia sought to replace CAD-based, wire-framing tools, SRK has actively promoted these implicit technologies, because of their scientific, commercial and economic benefits. Implicit Modelling defines an approach to...
International professional organisations in Australia, Canada, South Africa, USA, UK, Ireland, and many countries in Europe have adopted comparable codes, guidelines, and standards for mineral resource reporting. The definition of a mineral resource usually includes the requirement that “reasonable prospects for economic extraction” exist. This requirement implies a judgment by...
Dig line separating ore from waste using a cut-off grade
Resource Geologists are geologists who can value the basic underlying economic attractiveness of a mineral deposit. This means knowing the costs and practicalities of mining and processing for a particular product. A cut-off grade (COG) is an industry-accepted standard expression used to determine what part of a mineral deposit to...
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