This article was first published in the August 2024 edition of Engineering & Mining Journal. – By Carly Leonida, European Editor
E&MJ looks at how innovative grade control practices and technologies are giving operators greater sovereignty over orebody extraction.
The past two decades have witnessed a remarkable transformation in how mining companies approach grade control — determination of the threshold at which a material is deemed to be ore or waste — driven by a powerful combination of automation, digitalization, and a growing emphasis on sustainability.
“Traditionally, open-pit mines relied heavily on post-drilling blasthole samples for grade information,” Grant Caffery, Australia director at Clareo and former head of innovation at BHP, told E&MJ.
“Whereas today, GPS-equipped and sensor-laden autonomous drilling rigs have significantly improved precision [in sample collection]. For instance, Rio Tinto’s Pilbara operations have experienced a 25% increase in drilling accuracy and a 15% reduction in costs due to the introduction of automation. Additionally, inpit blasthole logging and down-hole sensors now provide real-time data on orebody variability, allowing for immediate adjustments during blasting to minimize dilution.”
In underground mining, while core drilling remains crucial, advancements in technology have accelerated the data collection process. Technologies like hyperspectral imaging and X-ray fluorescence (XRF) provide faster, more detailed analysis of mineral composition within cores, enhancing the core logging process.
“Real-time data analytics have become pivotal in modern mining operations,” Caffery explained. “Improved sampling techniques, combined with geostatistics, create detailed orebody models that boost predictability and reduce dilution. The integration of real-time data allows for immediate adjustments during mining, optimizing ore recovery and minimizing waste. BHP’s Escondida mine exemplifies this advancement, achieving a 10% improvement in ore recovery and a 15% reduction in costs in recent years through real-time data analysis.”
The advent of sophisticated ore sorting systems has further refined the grade control process. Hyperspectral imaging sorting technologies, as implemented by Plotlogic in an Australian gold mine, have increased ore recovery by up to 20% and reduced processing costs by 30%.
Machine learning (ML) and artificial intelligence (AI) are also transforming decision-making in grade control. AI-powered predictive models analyze vast datasets to optimize extraction processes, leading to higher productivity and reduced operational costs and downtime.
Caffery told E&MJ: “Efficient grade control practices also contribute to sustainability by minimizing waste and optimizing resource utilization. Industry partnerships, such as CRC ORE’s Grade Engineering approach, focus on early waste rejection, improving ore processing efficiency and economic returns by up to 30%.
”These advancements have made grade control practices more efficient, accurate, and sustainable, which translate to significant gains in productivity, profitability, and environmental responsibility for mining operations.
Trends, Challenges and Opportunities
According to Caffery, the grade control landscape is undergoing a radical transformation driven by a complex interplay of trends, challenges, and opportunities. Economic pressures are a significant driver, with fluctuating commodity prices and rising operational costs forcing companies to improve their efficiency and reduce expenses. Advanced grade control offers substantial cost savings and enhances operational efficiency, which is crucial for maintaining competitiveness.
Sustainability and environmental responsibility are of increasing importance, prompting mining companies to adopt methods that minimize their environmental impact and promote resource efficiency. This shift is vital for meeting regulatory requirements and stakeholder expectations.
“Declining ore grades are another major trend,” said Caffery. “As high-grade deposits become scarce, mining companies are turning to lower-grade resources, necessitating more precise grade control to ensure economic viability.”
Technological innovations are continuously reshaping grade control strategies. Automated equipment, such as drill rigs and haulage systems, coupled with digital platforms for data collection and analysis, enhance precision, reduce human error, and improve overall efficiency. Advancements in geophysical imaging, ore sorting technologies, and data analytics also contribute to this evolution. However, new technologies can present challenges as well as opportunities as they require integration with existing processes and infrastructure.
Caffery said: “Ensuring [technological] compatibility can be complex and expensive, and skilled personnel are required to operate and maintain these advanced systems. The rapid pace of technological advancements necessitates continuous adaptation and investment, which can be financially burdensome for mining companies.”
Lower-grade ores can necessitate higher processing costs and increased environmental impact, and Caffery explained that achieving efficient grade control in such scenarios is crucial for maintaining profitability. Sustainability implementation challenges also involve balancing economic performance with environmental responsibility and, inevitably, trade-offs must sometimes be made.
In terms of opportunities, Caffery said that AI and ML advancements offer significant opportunities in optimizing grade control.
“Predictive models can improve ore grade predictions by up to 20% in some cases,” he said. “Advanced orebody characterization techniques, such as geostatistical modeling and real-time data analytics, enable more accurate characterization and grade control. This is particularly beneficial for mining lower-grade deposits, as exemplified by Newmont’s Peñasquito mine.”
He continued: “These trends, challenges, and opportunities paint a clear picture: the future of grade control lies in advanced technologies, automation, and a commitment to sustainability. By embracing these trends and overcoming the challenges, mining companies can unlock a future of efficient, accurate, and environmentally responsible mining operations.”
Block model validation in Leapfrog Geo. (Image: Seequent)
The Power of Precision
Over the past two decades, orebody characterization and modelling capabilities have also undergone a revolution, driven by technological advancements and improved methodologies. These advancements have yielded a multitude of advantages. Key developments include:
- Enhanced data collection and imaging: high-resolution geophysical imaging, such as 3D seismic imaging, has provided detailed visualizations of orebodies, enabling more precise delineation of valuable resources. This has translated into reduced exploration risks and costs, allowing for better targeting of high-grade zones and minimized waste, ultimately improving ore recovery rates.
- The use of drones and remote sensing technology, equipped with LiDAR and hyperspectral imaging tools, has revolutionized the surveying of large and inaccessible areas. This technology has led to improved exploration efficiency, with a significant reduction in time and cost, and increased accuracy of geological mapping. Additionally, remote sensing supports ongoing mine monitoring, helping identify changes in orebody conditions and optimize extraction processes.
- Sophisticated modelling and analysis: Advanced 3D geological modelling software integrates various data sources, such as drill hole data, geophysical surveys, and geochemical analyses, to create detailed and dynamic models of orebodies.
- Geostatistical analysis and simulation techniques, have improved the accuracy of ore grade estimation and spatial variability analysis compared to traditional techniques like kriging. This leads to a reduction in dilution by minimizing the inclusion of waste rock during extraction, thereby increasing ore recovery.
- Big data and ML integration: These technologies identify patterns and correlations that improve the accuracy of orebody characterization and grade predictions, enhancing overall mining efficiency.
- Interdisciplinary approaches: collaboration between geologists, engineers, data scientists, and other disciplines has led to the development of integrated systems for orebody characterization and modelling. These efforts have improved resource planning and extraction strategies, optimized resource utilization and reduced the environmental impact of mining operations. Additionally, these approaches have improved the accuracy of resource estimates.
“By providing a more precise picture of the orebody, these advancements em- power mining companies to extract valuable resources with greater efficiency, optimize processing, and minimize their environmental footprint,” added Caffery.
Using reverse circulation drilling for grade control work enables mines to collect samples well in advance of blasting and provides better quality samples. (Photo: IMDEX)
Grade Control in a Sustainable Future
It’s worth remembering that while good grade control is critical for the viability and sustainability of future mining operations, it operates within the constraints of exist- ing extraction technologies. Caffery cautioned that, while grade control optimizes resource utilization and minimizes environmental impact, it is not a silver bullet.
“Good grade control offers substantial benefits,” he said. “Maximizing resource recovery becomes essential as high- grade ore deposits become scarcer. Precise grade control minimizes waste and maximizes the recovery of valuable minerals, leading to better profit margins and increased economic resilience through more stable and predictable operational performance. Accurate grade information allows for tailored processing strategies, minimizing energy and water consumption, which translates to lower operating costs and improved economic viability.”
It also demonstrates a commitment to environmental stewardship, which is crucial for maintaining a social license to operate. For example, reduced land disturbance means that smaller areas need excavation due to minimized waste movement. Optimized material processing requires less water and energy, leading to a lower carbon footprint. And less waste rock allows for more effective mine reclamation and rehabilitation.
“In the future, evolving environmental regulations will likely place stricter limits on waste generation and energy consumption. Good grade control positions mining companies to comply with these,” said Caffery.
Over time, incorporating AI, ML and real-time data analytics into grade control practices will generate continuous improvements in resource estimation accuracy, operational efficiency, and the overall sustainability of mining operations.
However, Caffery noted that the effectiveness of grade control has its limits. Even with perfect knowledge of orebody composition, limitations in current extraction methods can hinder the complete separation of valuable minerals from waste. Also, some minerals may be too fine-grained or lack a distinct signature, making them difficult to identify and separate using current technology.
“To achieve a truly sustainable future for mining, a multi-pronged approach is needed,” said Caffery. “Continuous improvements in grade control, including in data analysis, modelling techniques, and sensor technology, will further refine practices.
“Meanwhile, research and development efforts are crucial for creating new extraction methods with higher efficiency and better separation capabilities. This could involve advancements in selective mining techniques, new methods for efficient separation of fine-grained minerals, and sustainable processing methods that use less water and energy.”
By continuously refining both grade control practices and extraction methods, the mining industry can achieve a future where responsible resource utilization and environmental stewardship go hand in hand.
IMDEX’s BOLT solution allows for better blasting which minimizes overbreak and underbreak in underground mines. (Photo: IMDEX)
Know Your Orebody
As noted earlier, in open-pit mining, many companies have started to move away from blasthole sampling for grade control as it provides an imperfect sample. Instead, most are now opting to use reverse circulation (RC) drilling. This shift is primarily being driven by the ability to get ahead of tight drill and blast schedules, providing operations more time to think about their data and plan strategically.
Dave Lawie, chief geoscientist and chief technologist at IMDEX, told E&MJ: “The RC approach allows miners to collect samples much earlier — up to 18 months ahead of the drill and blast process — and the better sample quality allows for more extensive measurements to be made beyond grade to inform short- and medium-term mine plans.”
He reminded us that the economic value of mined material is a function of more than just grade; there are many properties that can make a block, or selective mining unit uneconomic to process despite grade control results indicating the material is above cut-off grade. For instance, properties such as material hardness, a tendency towards acid-consumption or preg-robbing (in the case of gold ores), are all modifying factors that control the economic value beyond grade.
“If we consider the true value of mined material, then really, it’s about material control rather than grade control,” said Lawie. “It’s a high-resolution version of orebody knowledge (OBK). RC drilling allows time to bring OBK to bear on a more informed version of grade control, taking modifying factors into account, and provides a better account of ore and waste delineation.”
One of IMDEX’s solutions that can be used in material control is BLASTDOG. This doesn’t typically measure grade (although it can in very specific circumstances), but rather it measures a range of independent physical properties of the rock mass. This provides high spatial resolution data, which isn’t something that mines have historically been able to obtain at a mining/bench scale.
Lawie illustrated this with an example, “The bane of many copper mines in South America are clay-rich zones,” he said. “BLASTDOG allows mines to measure detailed clay distribution which, when modelled with copper grade, gives a far more accurate economic view of the bench, and opens up tactical decision making related to ore/waste and stockpiling strategies. We have BLASTDOG operating in copper, iron-ore and coal mines in major mining regions around the world.”
For underground operations, IMDEX’s BOLT solution allows miners to survey the drilled path of production holes very accurately. “Again, while it doesn’t measure grade directly, it allows for better blasting which minimizes overbreak and underbreak, which are types of grade control in their own right,” Lawie added. “BOLT is relevant to almost any type of underground mining regardless of commodity.”
IMDEX is currently adapting the BLASTDOG sensor suite to run in underground production holes. This will allow high spatial resolution material control in underground mining.
“Also, because this is all quite spatially rich and dense data that many operations aren’t used to receiving, we’re working on a digital system that takes this type of data and automatically puts it through a geostatistical process to create a block model which miners can use in their plans immediately,” Lawie told E&MJ.
“Having this sort of data available at an appropriate spatial resolution allows companies to rethink their mining strategy and will enable them to do precision mining, cut down their energy consumption and reduce their carbon footprint; essentially all the things miners need to be doing in this environment focused on decarbonization.”
Maptek’s Vulcan Grade Control Optimiser allows operations to create objective, repeatable data-driven models and dig lines. (Image: Maptek)
Measure, Model, Manage
The mining industry can be slow when it comes to embracing new technologies, tending to favor existing systems and techniques over novel approaches. However, according to Geordie Matthews, geology specialist at Maptek, innovation and improvement in the grade control process are typically driven by economic demands on mining operations.
“Mining tends to follow a boom-and-bust cycle,” he told E&MJ. “When operations are put under stress after a downturn, innovation becomes more important. Focus shifts from quantity to quality, increasing profitability without needing to increase the volume of material extracted. Better sampling and logging, improved assay techniques, and more advanced software can help relieve the burden on mine geologists.”
Block model analysis using integrated workflows with Leapfrog Geo, Edge and Imago. (Image: Seequent)
Matthews explained that a pivotal advance in grade control — or, as he prefers to call it, ore control (OC) — over the past 30 years has been the development of material optimization algorithms that are underpinned by conditional simulation models, which allow a risk-based approach to material boundary definition. The greatest challenge is to reliably, objectively and quickly define ore based on value to satisfy budget and shareholder expectations. Selective mining has adopted these tools and any relatively homogeneous orebody without clear visual controls can benefit.
“Conditional simulation, more specifically Sequential Gaussian Simulation (SGS), has been used since the 1970s to optimize real world problems where estimation fails and sample data alone cannot force an outcome within practical tolerances,” explained Matthews. “For OC, conditional simulation has been a viable solution since desktop computing became commonplace in the 1990s, with optimization software arriving at a similar time. SGS and optimization was still time consuming yet provided high-resolution OC models, tight reconciliations and higher profits for any business willing to embrace it.”
Maptek’s Vulcan Grade Control Optimiser (GCO) allows operations to create objective, repeatable data-driven models and dig lines while reducing mundane tasks. Even the most complex of geology models can be solved using AI, such as DomainMCF (part of the Maptek Compute Framework suite), to give results comparable to explicit or implicit models in a fraction of the time.
“A customer in North America with several open pits compared their manual grade polygons, ranging in size from 10,000 to 200,000 tons,with GCO results and recorded improvements in value in the order of 1% to 12%,” said Matthews. “The manual process of drawing polygons and designating which materials go to which process, for example mill or dump, is a tedious job for production engineers.
“Quickly generating multiple scenarios creates higher-value options. The scriptable nature enables operations to perform tasks, such as evaluating the past six months of polygons overnight, so the next day an engineer can generate a spreadsheet for analysis. Automating the grade control process also enables geologists to conduct sensitivity studies on alternative scenarios for maximising value and reducing risk.”
By leveraging the power of cloud computing and optimized software, SGS models can now be completed in minutes rather than hours. Larger models become accessible for use throughout the mining value chain, from resource and reserves through to processing and logistics, providing confidence that what a business promises can be delivered.
Matthews added: “As commodity prices ebb and stabilize in the future, prioritizing quality over quantity will be pivotal to the success of mining operations worldwide. The ability to adapt OC systems to get the most out of a changing price environment will push mining companies and service providers to pursue new tools and technologies.”
In recent years, Deswik, which is best known for its mine planning and scheduling tools, has expanded its remit into geology with solutions for grade control.
“Our mine planning and scheduling tools are popular across the industry and a number of customers had expressed an interest in having tools for their geology teams that interface seamlessly with other Deswik products,” explained Nick Anderson, product line manager for Deswik.CAD and GeoTools. “Rather than pushing geological data into software from another vendor to create blast designs or block outs, which can be a clunky process, then bringing those back into Deswik for say, short-term scheduling, it makes sense to be able to do all of those things in a common environment.”
The idea behind this development was to help teams better collaborate through smoother, more efficient workflows based on a single data source. The result was Deswik. OreControl, a module specifically for geologists which sits inside of the Deswik. CAD mine planning environment, providing them with the tools to design and create high-definition grade control models, as well as dig blocks or block outs for open-pit operations.
In doing so, Deswik.OreControl bridges the gap between engineering, geology and production teams, allowing grade control to become part of a live system on site that multiple teams and users can contribute to.
Anderson told E&MJ: “We talked to nearly 40 different sites when we were developing this tool, and we found that there’s a huge range of complexity in the capabilities that people want from the software. These range from highly complex, conditional simulations for expert users, to a very simple, almost black box approach, where less experienced geologists can add data and get a plan.
“A lot of sites are struggling with skills shortages and want to simplify their processes and workflows to help support training and keep production on track. Deswik.OreControl was designed to accommodate this full spectrum of needs. It’s very quick to learn, and easy to use. We partnered with a well-known geostatistical software developer to create the kriging engines that power Deswik.OreControl, so mines can have confidence in the quality of the models they’re generating.”
For underground operations, Deswik.Mapping contains tools that help geologists to build an accurate, high-definition picture of geology at the face. That orebody knowledge can be exported into other packages, such as Seequent’s Leapfrog, to update geological boundaries in models and improve orebody knowledge, all of which contributes towards better grade control.
“Deswik.Mapping has been available since 2018,” said Anderson. “That’s well established in the market, and deployed at many sites worldwide. Deswik.OreControl is less than two years old. That’s proven popular with mines that are already using the Deswik ecosystem, but we’re also able to support greenfield mines that are looking to make a new deployment, or brownfield sites that are looking to shift their existing systems and processes to a common environment. We pride ourselves on partnering with our customers to support them over the long term and help them find solutions whatever their needs.”
Deswik has expanded its remit into geological tools with the launch of Deswik.OreControl for open-pit operations. (Image: Deswik)
Data for Good Decision Making
It’s clear that better decisions are made when informed by the right data. Geoscience data, which is vital for grade control, has seen an exponential increase in volume over the past ten years, and this needs to be managed effectively.
Pieter Neethling, segment director, mining operations at Seequent, explained: “Traditional manual data collection methods are rapidly being replaced by innovative digital workflows that leverage cloud computing and related technologies to deliver new and worthwhile perspectives for multi-disciplinary teams.
“It’s about making geoscience data accessible to those who need it when they need it and creating avenues for users to utilize and enhance the data value within a protected data exchange ecosystem, streamlining processes and improving collaboration. The adoption of cloud-based data management is enhancing the governance of mineral resources and provides an essential and reliable system-of-record.”
Mining companies today no longer look at software and data in silos, but instead as snapshots of a much larger picture.This makes connected workflows vital for bringing together data, aiding near-real-time modelling, and for providing key, up-to-the-minute insights that are vital for more informed decision making.
Neethling explained: “Continuous modeling in geological workflows is a dynamic approach that updates geological models as new data becomes available. This method contrasts with static models that remain unchanged after their initial creation. Continuous modeling allows for a more accurate representation of the subsurface by incorporating the latest observations and measurements.”
For example, measure-while-drilling (MWD) data allows models to be updated in near real-time, enhancing the integration of IoT enabled technologies, such as digital twins. Integrating underground and open-pit face mapping applications into continuous modelling workflows also allows for rapid model updates, along with implicit geological modelling — a tool that can enhance the workflow efficiency and user experience by dynamically — to integrate new data into geo- logical and resource models.
Seequent offers comprehensive grade control workflows for both open-pit and underground mining. Integrated into Leapfrog’s 3D modelling solution are two core solutions. First, Leapfrog Edge, an estimation tool that ensures smooth, productive workflows, with dynamic updates to grade control models based on changes to the geological model.
Seequent said this solution enables users to work with data using highly visual tools, such as domained estimation with boundary analysis, variable orientation, resource reporting, variography and block interrogation. Intuitive, flexible workflows and uncluttered workspaces accelerate the resource modelling learning curve. Users can hand off block models easily to other teams in common industry file formats.
The second solution – Central – brings all data together in a tracked and managed, centralized and auditable environment. Users can open and view 3D models directly from a web browser, and public scenes enable important 3D information to be shared with mine stake- holders or the public. Easily established alerts and notifications keep everyone up to date with the latest data.
Neethling said that Seequent’s solutions are widely used in grade control, and the company is actively partnering with other software companies to enhance grade control workflows, for example in blast movement and underground face mapping.
Gold producer, OceanaGold, is seeing the benefits of dynamic workflows and flexible data updates at its Waihi mine site in New Zealand, which is using a combination of Leapfrog Geo, Edge, and Central. Waihi’s geology team is integrating 3D photogrammetric imagery data with implicit modelling techniques to monitor daily production performance, communicate to miners, engineers and geologists involved in operational planning and report back to the business.
Abe Whaanga, OceanaGold’s senior mine geologist, said: “We have reduced grade control model turnaround time from around a week to a day. This reduces the time from ore development to stoping and brings benefits of up to $100,000 per stope panel.”
To address geoscience data interoperability challenges, including data siloed across niche applications and projects, gaps in data audit trails and lack of consistent schemas for data analysis, Seequent is building a unified data platform for geoscience data management, analysis, compute and visualization. This will enable customers and the industry at-large to collaborate and manage geoscience data in a single space. It will provide the foundation for integrated work- flows between Seequent solutions and third-party applications.
The company said that, in grade control, this will provide enhanced productivity and efficiencies through centralized data sources and integrated applications that streamline data analysis, allow dynamic geological modelling, resource estimation and conditional simulations.
Higher quality insights will be generated by bringing all specialist knowledge and data together for enhanced problem solving and collaboration in the moment, building on the existing cloud-based capabilities in the Central project model management solution. Greater flexibility will also be possible through a secure open ecosystem that offers seamless workflow interoperability or programmatic interaction through application programming interfaces (APIs).
Control in the Face of Uncertainty
To summarize, choosing the right cutoff grade is vital for a mine’s profitability and lifespan, influencing the availability of minerals to the market, with demand for critical minerals being an important factor.
As advanced grade control practices and technologies, including those discussed in this article, become more widespread, they will help to de-risk long-term mine planning. Additionally, short-term continuous modelling practices will help to drive down uncertainty by separating qualitatively related decisions from those affected by volatile prices and geological surprises.
“Effective grade control will be increasingly crucial for efficient and profitable mining operations, significantly impacting the return on investment,” Neethling concluded.