Can money mining and sustainability co-exist? The Whittle Consulting perspective.

In October, I attended the Whittle Consulting Money Mining and Sustainability seminar in Vancouver. Gerald Whittle, CEO and recovering management accountant, led us through two intense days. The focus – maximizing net present value (NPV) of mines.

Whittle Consulting’s mining optimization methodology, called Enterprise Optimisation, has been developed for over 30 years. It is built on multi-variable, non-linear algorithms to find the most economically attractive mining cases, subject to constraints that can be imposed by the user. The Whittle Consulting approach is integrated to consider mining, processing, financial and environmental factors.

The course centres on a fictitious but plausible copper-gold deposit called Marvin located in NSW, Australia. Marvin has a well-defined block model. Various capacity constraints are considered, such as for mining fleet, mill power, concentrate pipeline and stockpile size. The project is assumed to be generally constrained by mill power. Gerald demonstrates how an initial, credible mine design and plan can be improved by following a sequence of optimization steps that address cut-off grades, mining sequences, throughput and plant capacity trade-offs.

There are two main principles used to find the economic optima - activity based costing and the theory of constraints. Activity based costing is a method of understanding fixed and variable cost drivers, thereby relating production levels with operating costs. This is important for optimizing a mine plan, as the operating costs should be appropriately scaled for a given production level. The theory of constraints is a management philosophy developed by Eliyahu M. Goldratt and Jeff Cox in their book “The Goal”. I read it about 20 years ago and found it compelling and thought-provoking. The philosophy identifies bottlenecks, and manages the production process around them.

Enterprise Optimization can also be used to assess metrics of sustainability, including parameters such as water and energy consumption, and GHG, diesel particulate, and dust emissions. In one case, Gerald demonstrated that an optimized mining plan was also 25% more energy efficient on a per metal unit basis than a base case plan. This was primarily due to less ore tonnage treated due to higher mill feed grades, and less waste haulage due to a smaller, higher grade pit. These factors result in lower power and diesel consumptions respectively, in turn reducing GHG emissions.

More profitable mines mean there is more money for stakeholders to invest in societal improvements, and companies to invest in further exploration. There are other consequences of using the Whittle Consulting optimization approach. Increasing cut-off grade, and sending near-marginal ore to waste dumps will reduce the overall life-of-mine ore tonnes treated, resulting in shorter mine life and lower total metal production. Shorter mine life may impact on long-term employment opportunities, and lower total metal production means lower overall metal resource recovery from the deposit. These concerns can be partially alleviated by stockpiling near-marginal ore for treatment during lulls in mine production, or at the end of mine life.

Other thoughts came to mind for me. One way for a mine to improve NPV is to lower its discount rate, which can be achieved by lowering the risk profile of the project. Choosing more eco-efficient practices, and managing social license to operate are two sustainability related strategies that lower project risk, and may improve the attractiveness of the project to certain investors. This in turn may reduce the borrowing interest rate for the project.

The Whittle optimization algorithms will typically tend towards higher mill throughputs to maximize metal production, despite some recovery losses from coarser grinds, as this will maximize NPV early in the mine life.  Grind will get finer and throughput lower later in the mine life as the opportunity cost diminishes. It is important to have realistic estimates of the throughput-grind size-recovery trade-offs to ensure that recovery losses are correctly accounted for. Process engineers should work to make the separation circuit as robust as possible for coarse particle sizes and high throughput rates. Practical metallurgical improvements such as close attention to the classification circuit, and good flotation cell and reagent addition control may limit any recovery losses from higher throughput. Selection of flotation equipment that gives robust performance across a range of particle size ranges will also help. Such initiatives will improve resource recovery and further enhance financial returns.

Gerald says, “it’s not a metal mine, it’s a money mine”. Typically, the focus is on maximizing metal flow through the bottleneck to maximize profit. However, in a period of low metal prices, it may make more sense to leave ore in the ground until prices improve to improve future cash flows. Recently, Cameco took such action by placing some of its uranium operations on care and maintenance. Such actions must consider the shutdown and startup costs, and should include sensitivity analysis of future prices.

Overall, the Money Mining and Sustainability seminar was thought-provoking and informative. Case studies suggest Whittle software is a powerful, quantitative tool that can rapidly consider a wide range of mine plans and schedules within a range of physical, economic, financial, social and environmental constraints. Such a tool seems essential, in an increasingly complex world with rising stakeholder expectations despite declining metal grades and harder to process ores. I’d recommend the course to anyone interested in integrated strategic optimization of mining projects.

Social Licence to Operate: When Communities Become Advocates

Today in our Sustainability in Mining Blog, I’m introducing Isobel Alice O’Connell, a colleague from Vancouver. Isobel has over 15 years experience promoting and advising on issue management, sustainability strategy and stakeholder engagement. She is recognised for working to integrate social and sustainability performance into broader operational processes.

As Head of Social Performance at Qatar Petroleum, Isobel developed strategies and programs to mitigate human rights and stakeholder risks across the company, especially in the supply chain. She also developed and managed sustainability practices for two global consulting firms, where she designed and implemented guidelines, impact assessments/ strategies, reporting, training and assurance of non-financial performance indicators. 

Laurie: Isobel, thanks for sharing your experiences on the Social Licence to Operate (Social Licence). It is something we hear a lot about these days in North America. It was a big issue for Century Mine, where I worked at in Australia in the early 2000’s - an agreement with Aboriginal landholders was critical to allow the mine to proceed. We know that there are important challenges for resource development in Canada with respect to Indigenous and community stakeholders.

How do you understand social licence?

Isobel: I like how Pierre Lassonde, President of Newmont Mining Corporation describes social licence, ‘You don’t get your social license by going to a government ministry and making an application or simply paying a fee… It requires far more than money to truly become part of the communities in which you operate.’

In simple terms, social licence is the trust, ongoing approval and support by both a local community and affected stakeholders for an existing or to be constructed project.  It is important to point out, there is no one structure or right way to gain Social Licence, but rather it is "the duty to consult" concerned parties for broad social acceptance, and within the extractive industry the increasing interest in the social licence to grow.

Laurie: How did the term social licence come about?

Isobel: The idea of a social licence started in the mining industry some 20 years ago but has now been adopted the extractive industries dealing with a range of community concerns, fears or opposition, especially in regard to natural resource extraction and competing land use priorities. Ironically, when Canadian mining executive Jim Cooney coined the term social licence in 1997, he was talking about building support for mines in developing countries, not resource projects at home.

The term social licence draws attention to the difference between a legal permit and the social acceptance or legitimacy that is essential for a company to be able to survive, prosper and ultimately be part of communities that advocate both a company’s and industry’s interests. It is increasingly recognized by various stakeholders and communities as a prerequisite to development, or how to action a broader Corporate Social Responsibility (CSR) strategy as a platform to engage stakeholders.

Laurie: What would you say to people who say the process is just a corporate bribe?

Isobel: Ensure that the benefits of an operation outweigh the costs at the local level is the necessary first step in establishing the social licence. Then outlining and delivering legitimate benefits to the community regardless of whether it is a natural resource, or even the increasingly trendy renewable energy.

For example, over the last 4 decades, companies were generally welcomed by communities because they offered employment. While this remains true in many parts of the world, providing just jobs is increasingly regarded as not sufficient to earn a trusted place in the community. More is expected of both companies, and likely include legacy and/ or succession planning initiatives.

Laurie: In Canada, what would you say are ways social licence can be undertaken correctly?

Isobel: Some Canadian mining companies have been recognized for their commitment to social development through best business practices and CSR programs. They also participate in international initiatives such as the United Nations Global Compact, the Extractive Industries Transparency Initiative (EITI), and the Equator Principles.

Laurie: What is the best way for a resource company to approach social licence?

Isobel: To play a part in the broader “social contract”, a company will need to understand the broad socio-economic parameters of the region where a community is located and find opportunities to strengthen its operations.

Stakeholder engagement is the key to success. Getting involved in regional development forums, working effectively with other industries community development for the broader and long-term outlook of the region will be necessary. Maintaining good relationships with a wide range of well-connected stakeholders, and playing its part in the broader regional development. A company becomes part of a community. The community will advocate for a company’s interests. That’s the beauty of the often-symbiotic relationship that the social licence to operate can stimulate, but should never take it for granted. This diagram from On Common Ground Consultants summarizes it well.

On a final note, and one that shouldn’t be overlooked, a government’s political and legal framework is vital to a company’s capacity and willingness to restrain its activities within sociably acceptable standards. Strong democratic institutions with clearly defined social and environmental regulations tend to raise the overall quality and social acceptance of private sector practices so that companies will have an incentive to exceed legal expectations and meet socially desirable standards.

Laurie: Thanks very much for sharing your knowledge on social licence Isobel. I'm on the Community and Environment Society Committee for the Australasian Institute of Mining and Metallurgy (AusIMM) and I’ll share your thoughts with my colleagues there. Perspectives from different parts of the world are always appreciated. If any readers have further questions for you, or would like to discuss how you might support them on managing social licence risks, how can they reach you?

Isobel: Thank-you for letting me be Resourceful Paths inaugural subject matter expert interviewee. I'm always keen to assist companies with manoeuvring through the numerous international sustainability guidelines and standards currently being implemented worldwide. They too can show how a company is building its awareness and executing their social license to operate. Please contact me via my LinkedIn profile.

Can mining survive in the circular economy?

There’s been much talk in the environment community about shifting from a linear “take-make-dispose” economy to a circular one. The premise is that by mimicking natural systems, and focusing on recovery, reuse and recycling of materials, we can eliminate waste and reduce extraction of virgin materials. The promise is that we can decouple growth from resource and environmental constraints. It almost sounds like a path to putting the mining industry out of business. Is this the beginning of the end of mining? I doubt it, but some things will change.

What is the circular economy?

Mainstream discussion on the circular economy is recent, however it’s reflected in various concepts from the 1970’s to 1990’s, including Industrial Ecology, Biomimicry and Natural Capital. All focus on systems design, learning from nature, eliminating wastes, and inter-disciplinary collaboration.

The Ellen MacArthur Foundation was established in 2010 to accelerate the transition to the circular economy based on three principles:

  • Principal 1: Preserve and enhance natural controlling finite stocks and balancing renewable resource flows
  • Principle 2: Optimise resource circulating products, components, and materials at the highest utility at all times in both technical and biological cycles
  • Principle 3: Foster system revealing and designing out negative externalities

Innovate UK visualizes the circular economy through material loops and interconnections. © Innovate UK 2017. All rights reserved.

Up till now, mining is all about scale

Over the last 50 years, the mining industry has been extracting increasing ore volumes based on a "bigger is better" paradigm. This was financially rewarding, as larger equipment with automated control brought economies of scale and low operating costs, often in the form of huge open pit mines and processing plants. However, with scale comes more water and energy use, more GHG emissions and more wastes. This heads in the very opposite direction to the circular economy. Declining ore grades and waning exploration success force miners to spend more to bring metal production to market. Miners have underestimated the complexity of executing mega-projects. Capital cost and schedule blowouts, difficult production ramp-ups and stakeholder interventions have led to big investor losses.

Only higher metal prices justify the risks and costs for such projects. But higher metal prices reflect increasing scarcity and declining productivity in mining. They stimulate innovation for substitution and more resourceful use of materials. This includes redesign of products to reduce weight of material used, refurbishing and recycling. In the long term, these factors affect the viability of the current mining business model.

Economics, consumer demands and environmental factors are driving the circular economy

Today’s customers are increasingly looking to purchase products as a service, when and where they want them. This changes the relationship between materials ownership and standard of living. Citizens in many parts of the world are becoming more aware and increasingly concerned about the health consequences of pollution, and risks from spills and failures of mine tailings facilities. This is driving regulatory constraints on the mining industry, and incentivizing investment in recycling and renewable resources. Many consumers, particularly in Europe, now demand more transparency on the environmental performance of products, this is reported through the EU Ecolabel scheme.

There is also momentum towards a circular economy through product stewardship and extended producer responsibility, which places responsibility on manufacturers to account for and minimize safety and environment impacts from their products.

How can the mining industry adapt to the circular economy?

The circular economy can be an opportunity for the mining industry to adapt. Mining companies are starting to use renewable energy and increase water recycling, strategies which reduce overall emissions, risk and long term costs. Underground mines that selectively mine higher value ores and return paste backfill minimize waste. Some vertically integrated mining and smelting companies, such as the European base metals producer, Boliden, have business models based on both raw materials extraction and recycling. This allows them to find synergies in materials sourcing, resource recovery and meeting quality requirements. This is a more stable business model than the boom and bust swings of mining.

Ultimately, a circular economy will impose costs and consumer pressure on mines that generate a lot of waste and environmental impact. This will force changes to an industry that is currently trending to more waste and impact. It should make miners review relationships with downstream smelting, refining and manufacturing customers, and reconsider the case for some level of vertical integration into refining and recycling.  The mining industry, and professionals in it, should build their awareness of where they fit in the materials economy, and their ability to shape more sustainable supply and use of materials. Walter Stahel stated that “excellence in metallurgical and chemical sciences is a precondition for a circular economy to succeed.” As a metallurgist, I’m jumping on that band wagon!

If you’re interested to learn more and engage on the circular economy and mining, please look out for information on the upcoming session that I will be chairing at the 2018 SME Annual Conference in Minneapolis, MN. Email me at to find out more.

Cobalt for Batteries – who will control supply, how ethical and sustainable will it be?

Last Wednesday, I gave a presentation to the Berkeley Energy and Resources Collaborative (BERC) on strategic metals for batteries. There has been rapid growth in lithium-ion battery demand, for handheld electronics, electric vehicles and potentially battery storage to level out swings in renewable electricity generation. Tesla has built its battery giga-factory in Nevada, with big promises of economics of scale. These developments have stimulated prices of two of the critical battery ingredients – lithium and cobalt. Cobalt has been in the headlines due the concentration of supply from the Democratic Republic of Congo (DRC), ethical issues from child labour in artisanal mines and the opacity of the supply chain.

How and where is cobalt mined and refined?

Cobalt is almost exclusively mined as a by-product of copper and nickel mining. The richest sources are sedimentary deposits are on the DRC side of the African Copper Belt. There, ores are usually leached to recover copper metal and cobalt as a hydroxide powder. Most cobalt recovered from nickel comes from weathered, laterite deposits, which are found in Australia, Cuba, Madagascar and New Caledonia.

Glencore, one of the world's largest metals mining and trading companies, and Chinese interests have both been making major moves to increase their DRC cobalt reserves. Glencore recently increased its stakes in DRC copper-cobalt mines by buying up the interests of the controversial Israeli billionaire, Dan Gertler. Chinese interests have agreed to acquire the Tenke mine from Freeport McMoRan and Lundin Mining.

Glencore outlines its cobalt mining reserves in its 2016 resources and reserves statement. More than 90% of its cobalt reserves are in Central Africa, with much of the rest in its Murrin Murrin nickel laterite mine. In comparison, the Tenke mine reserves are estimated to contain 510,000 t Co (Lundin, 2017).

Glencore cobalt mining reserves at end 2016 (Glencore, 2017)

Glencore cobalt mining reserves at end 2016 (Glencore, 2017)

In 2016, Glencore produced 28,300 t of cobalt, 24,500 t from its African copper mines, and 3,800 t from its nickel operations in Australia and Canada. The Cobalt Development Institute (2016) reported global refined cobalt production of about 48,000 t in the first half of 2016, a rate of about 100,000 t per year. On that basis, Glencore supplied over a quarter of the world's mined cobalt last year. That's good news for Glencore shareholders as cobalt prices have doubled in the last year. Glencore's production is due to increase later in 2017 as it brings its refurbished Katanga operation back into production.

Extraction of nickel and cobalt from laterites is complex and relatively expensive, and several projects were approved for construction when nickel prices were far higher than today. This has resulted in financial pain for owners. For example, one producer, Sherritt International has faced multi-billion dollar write downs on its Ambatovy laterite project in Madagascar. Don't expect any significant increases in cobalt production from nickel laterite operations for a long time.

Ambatovy nickel-cobalt laterite processing plant, Madagascar. Source:

Ambatovy nickel-cobalt laterite processing plant, Madagascar. Source:

Cobalt Development Institute estimates that half the world's cobalt refining is done in China, with much of that sourced from mines in the DRC. With the Chinese acquisition of the Freeport refinery in Finland, Chinese refining control will be further extended.

Source: Cobalt Development Institute, 2016

Source: Cobalt Development Institute, 2016

Artisanal mining and ethical concerns

There has been much concern by NGOs about artisanal mining of cobalt in the DRC, due child labour, dangerous mining practices and environmental damage. CRU, a leading metals intelligence company, estimates 10% of the world's mined cobalt production may come from artisanal sources, and that much of the product is refined in China. Recently, Apple suspended one of its battery suppliers due to concerns of unethically sourced cobalt in its supply chain. After all, who wants to be associated with harm to kids in mines in Africa? On the other hand, artisanal mining can be a much needed source of income for many poor people in Africa.

Children sorting cobalt bearing stones in DRC. Source: Amnesty International, 2016,

Children sorting cobalt bearing stones in DRC. Source: Amnesty International, 2016,

How does this relate to Li-ion batteries?

Cobalt is one of the key materials used in the battery cathodes. There are various cathode chemistries containing different levels of cobalt. To date, the most common has been lithium cobalt oxide (LCO), which contains 7% Li and 60% Co by weight. Other cobalt containing cathodes include lithium nickel manganese cobalt oxide (NMC) which contains between 12% and 20% Co, and lithium nickel cobalt aluminium (NCA) which contains 9% Co. The Tesla giga-factory is designed to produce NCA cathodes (Pillot, 2016). Other chemistries contain no cobalt at all, e.g. lithium iron phosphate (LFP) and lithium manganese oxide (LMO). Some alternative chemistries have the advantage of being less flammable than LCO, an important consideration for consumers given the notorious Samsung Galaxy Note problems. High cobalt prices and supply chain risks may also stimulate greater efforts in battery recycling and substitution. Researchers and battery manufacturers will continue to innovate to make safer, cheaper and more efficient batteries. 

High cobalt prices will also stimulate new mines, some in more stable places like Australia and USA. However, such mines would need consistently higher cobalt prices to justify the capital investment, and cobalt has a history of price volatility - in 2008 it topped US$45/lb only to fall to around $10/lb in early 2016. In the meantime, Glencore and the Chinese will control cobalt mining and refining. Hopes for more ethical and sustainable cobalt supply will rest on greater transparency in supply chains, consumers taking a greater interest in where the ingredients for their gadgets and green cars come from, and cooperation between governments, mining companies and NGOs to ensure safe and responsible mining practices.


Glencore Annual Report, 2016, Accessed 6 Mar 2017

Christophe Pillot, Avicenne Energy, The Rechargeable Battery Market and Main Trends 2015-2025, IMLB 2016

Cobalt Development Institute, Cobalt News, 2016

Canadian Mineral Processors Conference 2017 – Innovation to Sustain Mining

In mid-January, I attended the 49th annual Canadian Mineral Processors Conference in Ottawa. CMP had over 500 delegates from across Canada, and countries including Australia, UK, USA, Mexico, South Africa and Finland. There were many papers that focused on innovation and sustainability in mining themes.

The conference opened with a presentation by Dominic Fragomeni, “The Need to Innovate: Celebrate the Past…Look to the Future”. He described some of the successful innovations in mineral processing such as adoption of fine grinding stirred mills, alternative flotation machines, and advanced process techniques for refractory gold ores, such as non-cyanide leaching (e.g. thiosulfate), pressure oxidation and the Albion fine grinding and leach process. Dominic posed the question about innovation in mineral processing – “is our effort too fragmented?” (in my opinion, yes!), and reiterated the need for collaboration to solve complex challenges facing the mining industry.

Two papers were presented on ore sorting, which has the potential to substantially reduce the energy and water consumption per unit metal produced from an ore. Brent Hilscher (Sacre-Davey) showed some promising results of sorting silver, gold and zinc ores using XRF (X-ray fluorescence) and XRD (X-ray diffraction) detectors. In one case, a silver mine in Peru, ore sorting allowed the mine to decouple mining method and cut-off grade from mill feed grade, resulting in higher resource recovery and lower operating cost. Therefore, the mine didn’t have to shut down. Other applications included scavenging high grade rocks from otherwise uneconomic waste piles. In one of these cases, this also had the benefit of lowering the gold associated sulfide content of the pile to prevent it from producing acid rock drainage - a win for both profit and the environment. A second sorting paper on pre-concentration of gold bearing quartz ores was presented by Jorn Rohlender (Outotec). The paper described the process for determining the amenability of an ore to sorting, then different levels of pilot tests to confirm viability of a full-scale installation. Case studies of orogenic gold deposits in Northern Europe were presented. Tests suggested that typically 75 – 90% of gold could be recovered by rejecting 55 – 35% of weight in the feed, resulting in head grade upgrade ratios of 1.9 to 1.4. The benefits included increased resource recovery, reduced transport costs from satellite deposits and lower energy requirements for grinding. 

Two papers were presented on cyanide destruction, which is an important unit operation to ensure that gold mines can maintain environmental compliance, and minimize the potential harm to bird and aquatic species surrounding their sites. Anca Nacu (Kemetco Research) described the different demonstrated cyanide destruction technologies and the advantages and disadvantages of their applications. The importance of test work and need to consider site specific conditions were emphasized. Neri Roux (Research and Productivity Council) described cyanide destruction investigations at Anaconda Mining’s Point Rousse gold project. It was found that by segregating the two residue sources, implementing new monitoring instrumentation and adding reagent addition controls, sodium metabisulfite (MBS) reagent addition could be reduced significantly, saving money. Further reductions were demonstrated with addition of ozone in conjunction with these changes.

Gabriel Garcia Curiel (Dundee Sustainable Technologies) presented a new method to stabilize arsenic from copper concentrates. This addresses a serious issue in the global copper and gold industries – a rising tide of arsenic that is coming from increasingly complex ores that contain arsenic bearing copper minerals such enargite (Cu3AsS4), tennantite (Cu12As4S13) and arsenopyrite (FeAsS). The technique sequesters arsenic by vitrification into a stable glass phase. The technique, which has been tested in a demonstration plant in Quebec, appears to be significantly cheaper than existing hydrometallurgical techniques that stabilize arsenic into the crystal phase, scorodite. This may make the difference between leaving a copper deposit in the ground, or mining and processing it economically and in an environmentally acceptable manner. 

Peter Mehrert (ALS) presented laboratory and pilot plant results from the HydroFloat (TM) technology that showed potential for substantial increases in the recovery of copper sulphides at coarse sizes (> 400 um). This technology may eventually support plants in reducing power requirements through increasing grind size prior to flotation, while maintaining metal recoveries. This results in lower GHG emissions, and makes tailings easier to dewater, which in turn can reduce costs and risks associated with tailings disposal.

Several other papers covered flowsheet and equipment developments to improve metal recovery and product quality, including flash flotation, the use of fine grinding and Jameson cell technology to increase nickel grades at an Australian mine, and pyrite leaching of tailings at Penasquito mine in Mexico.

During the networking breaks, I met some eager students and shared my perspectives on careers in mining, and the importance of sustainable practices in maintaining a viable mining industry. Overall, the CMP was an excellent conference. It was great to meet both old and new colleagues, learn about industry innovations, and reinforce the message that sustainable business is good business. 

A reunion with Professor Alban Lynch

This week, while I was in Brisbane, I had the pleasure of catching up with Professor Alban Lynch. Alban doesn’t travel much anymore, but recently he went to Melbourne to celebrate his induction into the Australian Prospectors and Miners’ Hall of Fame, for his services to innovation and research in mineral processing globally.

I first met Alban in 1990 at University of Queensland, during a 1st year engineering function to promote the Minerals Process Engineering stream. Amongst students, he was notorious for asking, on meeting them, “Hi, I’m Professor Lynch, what’s your name? What’s your GPA?”. He had his reasons - Alban was looking for students who were capable and driven to solve technical challenges in the industry. I met the cut-off standard, signed up for minerals processing, and soon Alban organized a vacation job for me at Broken Hill. On arrival in this birthplace of Australian industry, me and two other 18-year-old UQ students checked into the unglamorous Tourist Lodge on Argent St. We were introduced to the Chief Metallurgist, Fran Burgess, and soon were sampling the grinding circuit in the lead-zinc-silver concentrator on the southern end of the lode. We got practiced at laboratory screen sizing and data analysis, and were commended for the quality of our work to characterise the circuit performance. Fran would later become my boss for several years, I also worked with her at Elura, Century and Rosebery mines in what became a serious dive into the lead-zinc-silver metallurgical industry. 

Alban had other influences over my career. He awarded me my industry scholarship with Mount Isa Mines, which launched my career as a graduate. At university, he insisted that multidisciplinary collaboration was critical for industry success. The message stuck, I bought into this approach on graduation. I worked for one of his esteemed students, Dr. Bill Johnson, in Mount Isa. I hired and supervised several university students for vacation work at mines in Australia, recalling the value these experiences gave me early in my career. 

This week, we talked about industry challenges, particularly declining ore grades and the brain drain of industry professionals and institutions. While Alban was troubled by directions in recent years, he seemed hopeful that students, if provided the right practical opportunities, could learn and rise to industry challenges. There was a story of hope of JKMRC students visiting Penoles base metals processing sites in Mexico to help solve real plant problems.

Alban was curious about my goals for Resourceful Paths, particularly regarding energy efficiency and effectiveness. He asked many questions. How long did I think SAG mills would be considered the preferred answer for breakage circuits? What were my views on dry grinding and how might this help reduce water use in processing? How much did I know about the cement industry? Had I heard about advanced air classifiers? Had I researched compression grinding? Was the deterioration in metallurgical schools as bad in Canada as it was in Australia? What were my thoughts on the eventual mining and processing of the low-grade copper halo ore at Mount Isa? What was Fran’s role there? How was I going to change the industry as a lone consultant?

Alban, as always, wanted thoughtful reflection, planning and results. I collated my action list. “You need to find a university to collaborate with, preferably with graduate students that need practical assistance. Learn about cement grinding and classification. Visit operating sites and report back on their practices. Get the resources from wherever you can to make your consultancy work.” It was clear that I had much to think about. I was expected to find my own resourceful path, sustain my future and make a significant and practical difference to industry. As a good student, I intend to deliver on my homework.

Ore sorting and pre-concentration - potential to boost profit and ease risks

Ore sorting and pre-concentration methods are used to separate waste from ore, and direct materials to optimal processing or disposal destinations. For amenable ores, they can increase feed grade, lower ore throughput and operating costs, and reduce environmental impact.

Historically, sorting was done by hand, for example, at a zinc mine in Wisconsin around World War II. Hard waste rock was removed at the grizzly to prevent production bottlenecks and drop downstream operating costs.


Development of cheap bulk mining, crushing, grinding and flotation processed reduced reliance on such manual methods. However, grades from metals mines have been steadily falling, as richer, higher grade deposits have been mined out. Globally, grades at copper mines have fallen from over 1.5% Cu in 1980 to less than 1% this year (see below). Historically, much higher grades were mined, for example, over 8% Cu in Australia during the 1880’s (Mudd, 2010). 

Lower grades present challenges to mining companies and society - as ore grades decline, more energy and water is needed to produce the same mass of metal, and tailings and GHG emissions per unit metal increase. This is exacerbated as ores get more complex, e.g. harder to break, smaller mineral grain sizes and more intergrown mineral textures. Ore sorting and pre-concentration may help profitably tackle these challenges.

Modern ore sorting relies on sensors to detect properties of particles, and based on readings, respond with a control action. There are two methods:

  • Bulk sorting, where loads of material (e.g. in a shovel, in a truck or a length of material on a conveyor) are directed to a destination based on measured properties
  • Particle sorting, where individual particles are measured by a sensor, and those that meet certain criteria are ejected into a separate bin, by an air jet or mechanical diverter.

Bulk sorting can only be successful if there is sufficient heterogeneity in the ore (i.e. ore grade and properties vary spatially) and if sorting occurs before that heterogeneity is removed through mixing. Therefore, bulk sorting would work best close to the mining face and before any mixing and blending processes. Particle sorters are efficient on coarse particles, but machines tend to be limited to 300 t/h.

Sorting processes rely on speed of sensors to give accurate information in time to take a control action to divert off spec particles or material. Increased computing power has made this more viable in recent years. A variety of sensors are available, some include:

  • X-Ray Transmission (XRT) – for base metals, industrial minerals, diamonds (nickel sulphide example below)
  • Electromagnetic (EM) – for base metals
  • Near Infrared (NIR) – for base metals, industrial minerals
  • Colour – for base metals, industrial minerals, diamonds
  • Radiometric - for radioactive materials
  • Magnetic Resonance (MR) – under development for bulk sorting of copper ore (chalcopyrite)

Duffy et al (2015) give a more comprehensive review.

Source: TOMRA-Commodas Ultrasort, Sorting Opportunities, Sensors and Applications Overview: Why Send Waste to the Mill, Presentation, 2012

Source: TOMRA-Commodas Ultrasort, Sorting Opportunities, Sensors and Applications Overview: Why Send Waste to the Mill, Presentation, 2012

Aside from sorting, pre-concentration processes that exploit a difference in particle properties to upgrade feeds include:

  • Screen sizing, and discarding or redirecting low grade size fractions, e.g. nickel laterites are often screened to remove coarse particles, resulting in upgraded Ni and Co grades (Denn, 2000)
  • Dense medium separation, which is applied at several major lead-zinc mines such as Mount Isa and McArthur River in Australia, using cyclones filled with a suspension of ferrosilicon and water 
  • Gravity separation, e.g. using the Inline Pressure Jig, which is used at the Pirquitas silver-tin mine in Argentina (Gray, 2011)

Use of such methods requires that processing and materials handling systems are configured to be operable, efficient and cost effective. In the case of dense medium plants, this includes incorporating conveyors to transfer feed and sorted fractions, and selection of crushing and grinding equipment that is compatible with the upgraded ore from the dense medium plant.

Mount Isa Mines Lead-Zinc Concentrator Heavy Medium Plant. Source:

Mount Isa Mines Lead-Zinc Concentrator Heavy Medium Plant. Source:

The economic drivers for ore-sorting and pre-concentration are strong where:

  • Waste can be rejected with minimal loss of valuable metal – this requires ore characterization testing and benchmarking of technologies
  • Water, energy and grinding media unit costs are high - rejecting waste will reduce consumption of these, and therefore save operating costs
  • Reject material is hard and abrasive – further saving operating costs from power, media and equipment wear
  • Satellite deposits are mined some distance from a central processing plant – rejecting waste could reduce ore transport costs
  • Increasing ore grade and reducing tonnes allows mine and mill production to be debottlecked – this could lift metal production as well as dropping operating costs
  • Sorting or pre-concentration lowers deleterious components in ore, improving recovery and product quality
  • Tailings disposal options are limited – reduced tailings production may reduce tailings risks and enhance viability of safe options for disposal (e.g. tailings filtration, co-disposal with coarse wastes)

Economics can be evaluated by comparing:

  • Capital cost to install ore sorting or pre-concentration
  • Net change in operating costs, considering operation of sorting or pre-concentration vs. the drop in downstream consumables costs
  • Net change in metal production after accounting for metal loss from sorting or pre-concentration, and any impacts on downstream processes
  • Any incremental savings or costs associated with waste disposal (e.g. less tailings)

An example of the economic and environmental benefits of ore sorting at a Canadian gold project are described here. Estimated operating cost, GHG emissions and water consumption reduced by 50% to 66%. Lower tonnes at higher grade leads to lower operating costs and less wastes (sustainable business is good business!).

The mining industry owes its shareholders and stakeholders serious consideration of ore sorting and pre-concentration technologies to produce metals more economically and sustainably. Continued development of equipment, systems design and operating practice should see these technologies play an important role in the future of mining.


Gavin Mudd, The Environmental sustainability of mining in Australia: key mega-trends and looming constraints, Resources Policy 35 (2010) 98–115

Duffy, K, Valery, W, Jankovic, A and Holtham, P, 2015. Integrating bulk ore sorting into a mining operation to maximise profitability, in Proceedings MetPlant 2015, pp 273–287 (The Australasian Institute of Mining and Metallurgy: Melbourne).

In-Line Pressure Jig Preconcentration Plant at the Pirquitas Mine, A H Gray, G Delemontex, N Grigg and T Yeomans, MetPlant 2011, Perth, WA

S M Denn, C G Ferguson and S L Makin, Upgrade Ability and Geology of Cawse Nickel Ore, 4th International Mining Geology Conference, Coolum, QLD, 200