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Overview: Yesterday, Today, and Tomorrow Vol. 59, No.2, pp. 21-27

The Evolution of Technology for Extractive
Metallurgy over the Last 50 Years—Is the Best Yet to Come?

Michael G. King

About this Issue






This article is one of a series published to commemorate the TMS’s 50 years as a member society of the American Institute of Mining, Metallurgical, and Petroleum Engineers. Each of the papers, listed below and accessible in print and on-line in JOM’s page-turning issue, takes a historic view of an aspect of materials science and engineering. Among topics covered are light metals, electronic materials, extraction and processing, materials processing and manufacturing, structural materials, professional development, and the future of materials science and engineering.





Figure 1
A cut-away diagram of an Outokumpu flash furnace showing that primary smelting occurs in the reactor shaft.





Figure 2a
An illustration of the Mitsubishi bath smelting concept using lance injection of feed and the use of gravity to transfer reactor products by launders, thus eliminating the converter aisle.





Figure 3
The Sherritt Gordon autoclave leaching of zinc concentrates at Trail, British Columbia.





Figure 4
A picture of the Kidd Creek, Ontario plant. The metallurgical site, built around 1980, operates both a copper smelter and zinc roasters but does not have the signature smoke stack of pyrometallurgical plants prior to this date.





Figure 5
A cut-away diagram of a Noranda Reactor showing its capability of accepting diverse feeds by slinger, Garr gun, and tuyere injection.





Figure 6
The use of multivariate data analysis to monitor furnace operating conditions.















Questions? Contact
2007 The Minerals, Metals & Materials Society

After World War II the United States enjoyed a period of sustained prosperity that enabled individual companies within the nonferrous metals industry to finance their own technology development. Until the late 1970s there was a “Golden Age” in which the original technologies of the late 19th and early 20th centuries were significantly upgraded and modernized. But hard times came in the 1980s when the costs of energy and environmental compliance in the United States together with the lack of anticipated growth in second and third world economies, and the rise of off-shore competition plunged the industry into a depression. Fortunately, our industry rose to the challenge and resurrected itself—in many ways thanks to the adoption of new technologies and their integration into a new global economic model. We have now entered a new Golden Age as the supplier of materials to emerging economies and we are doing this by harnessing the power of the computer and its link to the global availability of information.

Over the last 50 years TMS has published a number of detailed reviews relating to specific technology developments. Because the topic is so broad and in the interest of brevity, this paper presents a general and somewhat personal review of the history of technology since TMS became a member society of the American Institute of Mining, Metallurgical, and Petroleum Engineers (AIME).


When considering the current state of the industry it should be noted that, even though we are very effective recyclers of our products, we still have to work hard on improving our “green” image.

Because we are a mature industry operating in large visible units there is no doubt that we have left a noticeable footprint where we have conducted our activities. It is hard not to notice large open-pit mines and smelter stacks. Yet, when faced with the challenges of rising environmental standards our industry has responded with massive investment which has resulted in very noticeable benefits in nearly all the communities we work in. This has occurred in conjunction with improving on our already good recycling track record. The nonferrous metals industry (NFMI) has had a significant recycling component ever since humans discovered that remelting a used or broken metallic tool was an effective source of feed for making new implements. More recently, at the end of the 19th century, the Guggenheims recognized the value of their scrap metal operations in Philadelphia and grew the business into one of the original great American mining companies. As the impact of humans on the environment became a real issue in the 1970s, the NFMI, like everyone else, had to step up its environmental and recycling performance. More stringent environmental regulations coming into effect at the same time the industry was facing a downturn put severe pressure on all companies. Some, such as Anaconda, could not stay in business and plants such as the Asarco El Paso lead smelter were no longer economically viable. But many positive things came from the forced changes and perhaps the best example is the closure of the sulfur loop where it is now accepted that, in pyrometallurgical operations, SO2 will be captured and made into sulfuric acid. An example of a modern smelter is shown in Figure 4.

In turn, this sulfuric acid can be used again by industry in applications such as leaching oxide ores or leaching of sulfide concentrates. In hydrometallurgical applications the process is sometimes tailored to yield elemental sulfur as a commercial product, an example being the Sherritt Process for leaching zinc concentrates. The sulfur can then be shipped to a new location for conversion by burning into sulfuric acid and so closing the loop. Most metallurgical operations must also deal with fugitive emissions and water discharges. Nonferrous smelters have always recycled their dusts internally because they contain significant metal values. Today it is also possible to recycle such dusts in dedicated recycling facilities using robust technologies such as IsaSmelt, Ausmelt, and the Noranda Reactor (Figure 5). Another significant dust recycling technology is the use of the well-established Waelz kiln to fume the large amount of zinc contained in electric-arc furnace dust generated by the iron and steel industry. And in a related context, the lead industry has had a record of fuming both zinc and lead from slags for recovery and recycling. A variety of technologies has been developed to do this, including electric furnace and plasma arc fuming.

The NFMI has also put a considerable effort into ensuring that aqueous discharges from mines, mills, smelters, and refineries meet stringent standards. The most common technology used is simple alkaline precipitation of heavy metals, usually with lime or sulfide, and subsequent recycling of the precipitates to smelters or solid waste treatment plants. These precipitates or sludges are often excellent feeds for smelters employing technologies such as IsaSmelt or AusSmelt or the Noranda Reactor because they can accept moist, variable feeds. Often technologies such as high-density separation and reverse osmosis are used to improve the effectiveness of metal removal from the discharge streams.

Another closed loop has steadily evolved over the years with lead. Because of understandable environmental concerns, lead has essentially evolved into a one-market metal—in lead-acid batteries. The components of these batteries are fully recyclable—lead metal alloys, lead oxide paste, plastic separators and cases and, of course, the sulfuric acid electrolyte. Recycling rates for batteries now run in the high 90 percent range and the public has no reason to discard batteries irresponsibly. This means that the lead industry in the developed world is now totally dominated by the secondary (recycling) industry. Technology development for lead has focused on the need to be able to accept the variable feeds coming from the recycled batteries.7

Higher-value metals, such as nickel and cobalt, when used in products such as nickel-cadmium and lithium-ion batteries, can be valuable sources of feed to nickel smelters. Even higher value metals such as precious metals and platinum group metals (PGMs) have always had high recycling rates. Precious metal scrap, especially from the electronics industry, is aggressively sought by primary copper smelters such as the Horne (Canada) and Umicore (Belgium), which have elected to install flexible feed technologies such as the Noranda Reactor and IsaSmelt, respectively.

Nickel smelters are useful conduits for the recycling of PGMs because their downstream refineries are already set up for recovering these elements. Electric furnaces such as the Xstrata furnace at Sudbury in Canada can readily accept PGM feeds. Sometimes PGMs are in a discrete enough form, such as in automobile catalytic converters, that a standalone technology like plasma smelting can be used in a dedicated plant.


The nonferrous metals industry (NFMI) as we currently recognize it essentially came together in the late 19th and early 20th centuries. It was the early corporate giants from this era such as Asarco, Phelps Dodge, Anaconda, etc., which supplied the metals and materials to America as it developed its infrastructure on the way to becoming the world’s preeminent economic power. The numerous technologies initially developed for metallurgical processes were characterized by the personal attribution given to the inventors, such as the Peirce-Smith converting of mattes and the Betts process for refining lead.

All of this changed in North America after World War II. Since there was no war damage to overcome, the economy came out of the Great Depression and took off. The concept of suburban living as being ideal for families grew enormously. This led to huge expansions in home building, new appliances for these homes, multiple automobiles for one family, and the ability to travel long distances by car and plane.

The NFMI reflected these expectations, with many companies expanding their activities to improve their profits by including downstream and added-value products—a “soup-to-nuts” approach. The desire to integrate downstream resulted in the formation of operations and subsidiary companies to produce refi ned by-product metals, specialty alloys, metal powders, advanced materials, custom chemicals, etc. Indeed, the author, who has a historical background in this area, has frequently given a presentation titled “The Production of Minor Metals—or How to Get the Squeal out of the Pig.”

Companies were greatly assisted at this time in their technology development by the quality of their labor force, many of whom were funded in their education by the G.I. Bill. When these people entered employment following university they also were joining well-established companies with guarantees of long-term employment. When the author came into the industry in 1974 the majority of his senior co-workers were coming to the end of such careers and they were able to internally provide vast knowledge and experience as well as mentor newcomers. The stability of the work force and its role in technology stands in stark contrast to the situation today where there is often no corporate collective internal memory and knowledge must be gleaned from outside sources.

So what exactly is the technological legacy of the period from World War II to the late 1970s and why is it considered to be a Golden Age, as first defined by Nicholas Themelis in 1993?1

Most of the physical plants for the NFMI industry built in the early days of the industry were in need of technological retrofits and upgrades. Many companies were financially strong enough to set up corporate R&D centers to provide them with the technologies they would need to grow their businesses. Typical of this genre were the technology centers built by Asarco (New Jersey), Amax (Colorado), and Kennecott (Massachusetts and Utah) as well as the Noranda, Falconbridge, and Inco facilities in Canada. The mandates of these centers varied. At one end of the spectrum there were the blue-sky hopes of the Ledgemont Laboratory, built by Kennecott, at a location remote from operations and using a model loosely based on the Bell Labs concept—put enough intelligent people together and they will invent something useful. At the other end development was done at or close by operational sites. But it was accepted that technology development would be driven internally from the corporate technology “silo.”

So the expected happened. Faced with the same technical challenges of a relatively mature industry, each company came up with its own solutions. This resulted in the emergence of a wide variety of technologies for the generic problems of the industry, particularly the need to process declining ore grades in North America.

In his address to the AIME on its centenary in 1970,2 Herb Kellogg noted that technological progress fell into three categories: The Bigger and Better Process, The New Process by Virtue of Engineering Design, and The New Process by Virtue of Novel Chemistry. Not surprisingly, as we review progress in 2007, Kellogg’s characterization has stood the test of time.

His category of the Bigger and Better Process was linked, as noted previously, to the fact that the overall grades of ore available to the mature North American industry had started to fall. More tonnes of ore had to be mined and milled to sustain production tonnages of metals. There was a matching need to increase throughput to lower the unit cost of production and this was most easily achieved by increasing the intensity of the processes, improving mechanization—greatly assisted by the introduction of the first microelectronic devices—and increasing the physical size of the plants.

An illustration of the Bigger and Better Process is the Amarillo Copper Refinery (ACR) opened by Asarco in 1975. The refinery capacity was set at 480,000 t/y and it replaced three refineries built in the late 19th century with a combined capacity of about half that of ACR. With respect to a better process, almost immediately after ACR was commissioned, Mount Isa Mines and Kidd Creek realized that plating a sheet on stainless steel could be continued for at least seven days to make directly saleable cathode and eliminate the need to make a precursor one-day starting sheet. Since the early 1980s this is the only technology used in new copper refineries.

In smelters the need for energy efficiency and improved hygiene was becoming apparent. The industry recognized that operations such as the roaster/reverb smelting used for copper concentrates were not economical for the handling of much larger tonnages of concentrates. The change began when Outokumpu and Inco started work on the concept of flash smelting in the 1940s. The need to intensify the smelting process was further addressed by the addition of oxygen injected through burners, tuyeres, or lances. This was technology transferred from the basic oxygen furnace developed for the steel industry.3 At the same time, furnace life was greatly improved by the adoption of cooling technology within the furnace refractories. A variety of new smelting technologies emerged. The Inco and Outokumpu (Figure 1) technologies are characterized by the injection of oxygen through the concentrate burners whereas Mitsubishi (Figure 2) and IsaSmelt technologies take advantage of injection lances to increase smelting rates by agitation of the bath. The Noranda reactor and the El Teniente converter, developed in the same time period, exhibited another variation of process intensification by injecting concentrates through submerged tuyeres. All of these technologies have driven up the copper grades of the mattes being received by the converters, thus enabling them to match the increased capacities of the smelting furnaces feeding them.4

These smelting technologies, which rapidly became commonplace in the 1970s and 1980s, soon moved into the second phase identified by Kellogg as the New Process by Virtue of Engineering Design. The advent of smelting concepts such as the Noranda Reactor (for copper) and the QSL and Kivcet reactors (for lead) represented attempts at using a single reactor for the entire smelting process. Although the Noranda Reactor has not evolved into a single-step commercial process for copper, both the QSL and Kivcet reactors are now used commercially for lead smelting. The Teck Cominco Kivcet reactor at Trail, British Columbia, stands out as a testament to a process where lead concentrates are fed to the furnace and slag-free hard lead bullion is tapped from the same reactor as a final product.

In the zinc and nickel industries the third category of development—New Processes by Virtue of Novel Chemistry— has appeared.5 Traditionally, zinc sulfide concentrates were roasted to oxide and then leached. In 1981, Sherritt Gordon together with Cominco developed a process (Figure 3) to pressure leach the concentrates to dissolve the zinc and convert the sulfur to its elemental form for recovery. The first plant was installed at Cominco, Trail, in 1981. For nickel, the challenge was of a different nature in that most the world’s nickel resources became lateric (oxide) ores versus the sulfide ores which had been the mainstay of the industry since the early 20th century. Lateritic processes were originally developed for Cuban ores. The Caron process, a pyro/hydro hybrid, was introduced as the first commercial process in the 1940s and was followed by pressure acid leaching in the 1950s. These processes required a hydrometallurgical back end so that nickel and cobalt in limonitic ores could be separated. In the 1960s and 1970s the focus switched to saprolitic ores which contain little cobalt but are high in acid-consuming magnesium. As a result, fully pyrometallurgical processes emerged, especially the rotary kiln electric furnace (RKEF) process which dominates today. The saprolitic processes send reduced nickel and partially reduced iron to electric furnaces for final reduction to metal as ferronickel.

Interestingly, the current challenge facing the lateritic nickel industry is how to get Bigger and Better to meet world demand for nickel. The inability to upgrade laterite ores handicaps development of new processes which are now required to be energy efficient and meet stringent global environmental standards. Currently, there is no limonitic plant with a capacity of >55,000 t/y and the largest saprolitic plants still produce <100,000 t/y nickel. The main reason for this lies, of course, in the fact nickel in laterites is locked in solid solution and cannot be beneficiated like its discretely mineralized sulfide cousin. Laterite plants must process feeds containing only 1–2% nickel whereas some smelters may see sulfide feeds as rich as 18% nickel. The nickel laterite industry stands at a crossroads as it struggles to bring on significant new capacity for such low-grade feeds.

In summary, from the end of World War II to the early 1980s, the NFMI had a wide range of options if it either wanted to upgrade a plant or install a greenfield operation. The reader will have noted a decided trend in the text so far—a “silo” model of technology development reflected in the fact that new process names came directly from the companies that invented them. Typically this is reflected in the process nomenclature arising from this period such as

  • Outokumpu, Inco, Mitsubishi, Noranda, IsaSmelt, QSL (in part) smelting processes for sulfide concentrates
  • Isa Process, Kidd Process for the direct plating of copper
  • Sherritt Gordon and CESL leaching processes for sulfide concentrates
  • Asarco shaft furnace for copper cathode and anode melting

There are a reasonable number of North American names in this list but the international component is also very high. This indicates that globalization was starting to impact the industry by the 1970s. At that time the business model was for companies to have overseas affiliates operate as separate entities with little communication with the parent company. But the international value of technology transfer was becoming noted and by the early 1980s companies such as Outokumpu, Mount Isa, and Mitsubishi were capable of marketing worldwide.

As the 1970s came to a close the NFMI was in reasonably good shape. The oil industry, cash rich due to the high price of oil, viewed base metals companies as places to invest. New owners such as Exxon, Atlantic Richfield, and Sohio joined the ranks with such long-established companies as Phelps Dodge, Asarco, and St. Joe Minerals. In the short term there was a technological stimulus due to the (ironical) need for NFMI companies to become much more energy efficient now that energy costs had risen significantly. Also, the needs for environmental compliance were becoming significant and companies needed to spend capital for sulfur dioxide capture as well, ensuring that atmospheric metals emissions and aqueous discharges met the new standards.

But it turned out that storm clouds were on the horizon and there would be a significant delay before the NFMI truly benefited from the Golden Age.


At the start of the decade NFMI companies were doing well due to the consequences of high inflation. As noted previously, there was ongoing recapitalization of the NFMI with commitments to installations such as the Inco flash furnaces at Chino and Hayden, the Mitsubishi furnace at Kidd Creek, Sherritt Process installations at Trail, Kidd Creek, and Hudson Bay, and the Outokumpu flash furnace at Hidalgo. Also the need to strive for much better environmental compliance meant that companies had started to invest significant dollars in SO2 capture in the form of sulfuric acid plants. Aqueous discharges—both mine tailings and smelter and refinery eluants—were of concern and water treatment became mandatory at many NFMI sites.

The investment in technology at corporate research and technology centers helped to mitigate the impact of higher costs of energy prices and environmental compliance. However, the industry could not fight off indefinitely the effects of the recession in the early 1980s, allied to the lack of predicted growth in less developed nations. There also has been a number of events such as the nationalization of the Chilean copper industry which discouraged fresh capital investment in the NFMI at this time. The industry went into a prolonged swoon, from which, at one time, it looked like the North American companies would not recover. Metal prices plunged and in 1984 Business Week magazine proclaimed the “Death of Mining” on its cover.6 It also became apparent that the United States was now in serious competition with the lower cost of metals production in various places around the globe, especially in countries such as Chile, Mexico, and Peru.

By 1985 the NFMI in the United States was in deep trouble. Companies were near bankruptcy and senior managements all over had cut costs to address the issue by conducting fire sales of assets, closing plants, and reducing corporate overhead in functions such as technology centers. Whereas the 1950s and 1960s saw the rise of the corporate technology center, the 1980s saw their wholesale decline in North America. Also the oil companies, flush with cash at the start of the decade, started to bail out of their “underperforming assets,” which only worsened the situation. The deep gloom persisted from 1983 through 1987, when the first signs of revival appeared. Interestingly, this came from companies that had kept faith in technology. Although formal corporate support of technology was no longer strong, the legacies of the Golden Age came to the rescue. Phelps Dodge, a company which appeared headed for bankruptcy and closure in 1984, invested in heap leaching/solvent extraction technology for the unique chalcocite mineralogy of the Morenci mine. They were able to turn the fortunes of the company around in a few years. By the end of the decade, Phelps Dodge had returned to its preeminent position in American copper producers by extending this low-cost option for producing high-grade copper to a number of heap-leaching operations.

Magma Copper invested in Outokumpu flash smelting at San Manuel and eliminated the last major SO2 output from a U.S. copper plant. Other bold steps in technology taken at this dark time included Cominco’s installation of QSL smelting at Trail (later to be switched to Kivcet) and BP’s multi-phase investment in Kennecott Utah, where it completely revamped the process from mine to refinery by installing the following technologies: large-scale open pit mining, large-scale semi-autogenous grinding milling, installation of a 1 million t/y capacity smelter with both flash smelting and decoupled flash converting, permanent cathodes for copper electrorefining, and more than 99% sulfur dioxide capture. Other companies followed suit and by the end of the decade further commitments were on the horizon, such as the Cyprus IsaSmelt reactor at Miami and the Asarco ConTop cyclone smelting process at El Paso. In addition, Noranda adapted its single blister-making concept to a large-capacity process producing very high grade (75%) matte.

By the early 1990s the U.S. NFMI was in much better shape, although nickel was adversely impacted by the collapse of the Soviet Union and the accompanying flood of stainless steel scrap that came on the market. However, significant permanent change had occurred in how companies viewed technology development. Most companies had begun working as integrated worldwide entities, assisted by the beginnings of true globalization. In part, this was due to the advent of much improved communication arising from the microelectronic revolution, manifested in the form of satellite telephones, telefaxes, and ultimately the introduction of e-mail and the Internet. Using these tools, global information exchange became available to everyone in the industry and gave every company the ability to develop “virtual technology” concepts.

The NFMI also moved strongly to take advantage of economies of scale. Mines became larger, thus driving down the cost of the most expensive part of our industry—mining and milling. The increased outputs from such operations forced smelters and refineries, in turn, to increase capacity.

Fortunately, the technological legacies of the Golden Age allowed the downstream operations to match this change. In two decades the industry moved from smelters typically producing 100,000 t/y of copper in roaster/reverb operations to flash and bath smelters, some with the capacity to treat in excess of 1 million t/y of concentrates producing over 300,000 t/y of copper. Copper refineries expanded to 500,000 t/y or greater capacity. Their production was greatly helped by permanent cathode technology being expanded to 10–14 day plating cycles and by reagent control technologies such as Reatrol® and Collamat.® Now current efficiencies in copper tankhouses are often 95% or better.

In the zinc industry the invention of the jumbo cathode by Vielle Montagne in 1969 led to the building of refineries with 250,000 t/y or more capacity. This came about by the development of mechanical stripping which decoupled production from the size of a plating sheet capable of being handled by an individual. Instead of hand harvesting after 1 day, some zinc tankhouses can mechanically harvest three-day jumbo cathodes from sheets with three times the surface area of the manual processes. For nickel, investment switched primarily to the building of plants for processing laterites by the RKEF method although there was also investment in the flash smelting of sulfides by Inco and Outokumpu.

Only the lead industry, which saw its focus change overwhelmingly to treating secondary materials from batteries, did not see the same level of investment in new technology. See the sidebar for environmental developments in NFMI.


The late 1990s/early 2000s saw the NFMI once more in a depressed state. A global economic downturn sparked by such events as the Asian currency crisis and the prolonged Japanese recession put the NFMI in a state of surplus capacity for most metals. But luckily, the Chinese Dragon was about to wake up! The demand from China for all commodities brings to mind an experience of the author in 1981. In that year Charles F. Barber, then the chairman of Asarco, pronounced in a farewell speech that metals are “the building blocks of civilization.” It turns out that Barber was correct because, of course, the Chinese are now in the process of building their industrial civilization using our metals as building blocks.

Our operations are stretched to capacity and prices have risen to unprecedented levels. Ironically, this has brought with it the paradox that costs of materials for new NFMI plants, as well as the contingent engineering services, have risen to the point that greenfield installations need to be justified on totally different economic parameters than from just 5 years ago. When the author entered the nickel industry in 1998, a 66,000 t/y nickel laterite plant was predicted to cost $1.5 billion to build ($12/installed annual lb.). Such a plant could meet a 15% hurdle rate at long-term nickel prices between $3–3.50/lb. The economics of such plants have doubled since then and, in 2007, companies are being required to risk capital based on nickel prices which now must clearly average $6–7.00/lb. for the life of the project—prices which are currently realizable but have never been seen on an extended basis.

So how are we going to resolve this paradox and move to even better times? Simply, we need to be smarter and harness our metallurgical and mechanical engineering needs to the virtual world of the microelectronics engineer. If this is done successfully the best may be yet to come for our industry.


Consider so far the impact of the electronic age on our industry. This article has already noted our ability to communicate effectively on a global basis. Global standards of engineering can be easily implemented no matter the location of the operation or project. The technology of the high Andes is the same as that of the Indonesian jungle as the plains of Western Australia. The availability of the Internet means that engineers have ready access to the same level of information no matter where they work.

What information are we talking about? We are referring to tools such as mathematical modeling of processes with techniques such as MetSim, Aspen Plus, and FactSage, which can access all the electronic data bases that have been set up. This does not mean the technical librarian and corporate memory are no longer needed but instead that all of this knowledge can be combined to greater effect.

The ability to use information electronically means we can try and test our thermodynamic, kinetic, mechanical, and materials of construction assumptions before we do a major test. Design of experiments minimizes the costs of the actual test programs and also maximizes the information to be gleaned. There is frequently a mandate to produce data from such tests which will meet a 95% confidence limit. We can move forward to the piloting, demonstration, design, and detailed engineering phases of technology implementation knowing that we have identified a robust process. The additional value of inserting maintenance and materials issues in to the virtual design process cannot be over emphasized.

Similarly, the value of process control must be recognized. In the 50 year time span being reviewed in this paper, process control has emerged from its infancy in instrumentation—sensor alarms, level controls, etc.—to the much higher levels of operational prediction and performance optimization. An example is the use of multivariate analysis techniques8 in smelters to alert operators when furnace run-out conditions are being approached. Figure 6 illustrates how a large data set derived from thermocouples, particularly at the bath level, is used to set boundary conditions relating to a safe operating mode and predict the onset of run-out conditions. Expert Systems is another powerful tool to help operators run their plants at optimum levels. Since our industry no longer possesses the technical depth it once retained in its corporate organizations, we must be even more aware of what the outside world has to offer. As the fluid bed reactor was brought in from the petroleum industry to replace tray and hearth roasting, so we must look elsewhere for more novel technologies. Both pyrometallurgy and hydrometallurgy are forms of applied chemistry and we can expect the world of chemical research to bring us new developments. An example is the use of computational stereochemistry to create essentially designer chemicals for hydrometallurgical applications. Two such technologies are the application of crown ether molecules (already commercial) and zwitterionic ligands to selectively extract targeted ion pairs from solutions.10

We are just beginning to see the impact of the biological revolution on our industry.11 It has long been known that bacteria greatly impact heap leaching. The ability to develop new strains of bacteria which can resist higher temperatures and toxic impurities in ores is slowly but surely impacting our industry. As we look forward to a bright future a word of caution is inserted. As powerful as the computer is and the accompanying virtual world, there is still no substitute for an engineer who has a grasp of the real world. Engineers must be able to work in a plant environment so they can develop instincts on how things are working. It is similar to the advice that the author received when solving mathematical problems as a student—does the answer make sense? If not, why not?

The NFMI will continue to operate smarter, to be more energy efficient, and to work to meet ever more stringent environmental standards. At some point we can expect to see the next generation of breakthrough technologies that will impact our industry. Mostly likely they will either be seen in the mining sector, which incurs the highest part of the cost of producing metal, or the milling sector, which incurs the greatest losses of metals values to reject tailings.

The signs are there. In mining the efforts to develop in-situ mining of the 1990s such as the copper leaching processes in Arizona at Casa Grande, (USBOM, Asarco, and Freeport McMoran) and Florence (BHP) will likely be revisited because the concept is elegant. The process leaves no footprint above ground and the pregnant solution produced can immediately go to a refinery. We can also look forward to increasingly automated mining which will allow us go to areas, particularly at a depth where ground stability currently makes it unsafe for human miners. Many ore bodies are richer at depth (e.g, Cu/Ni in Sudbury, Ontario and copper at Superior, Arizona). In milling, technologies such as ultrasonic comminution may significantly drive down milling energy costs. This may be allied to synergistic technologies such as advanced process mineralogy.12 This technology is today based on the advanced quantitative capabilities of QEM*SCAN® and MLA® analyzers which can accurately measure the mineralogy of thousands of particles in a sample. In turn, the data can be used with mathematical certainty to develop virtual flowsheets which identify the optimal grinding sizes needed to recover pay metals locked in the mineral grains. Additionally, this can be further linked to ultrafine grinding technologies which have overcome the problem of fine slimes flotation. All of this results in the much improved economic performance of milling circuits. Downstream smelters and hydrometallurgical plants can now receive higher-grade feeds with much less metal value being lost to the tailings dam. So getting the “squeal out of the pig” is being moved back in the process stream from the refinery to the mill.


With the prospect of a Supercycle in the years to come, the NFI has the ability to serve the world even more effectively, particularly if it harnesses the power of the microelectronic revolution and applies it to novel technology development.

As a final comment, this account of technology development over the last 50 years serves as a testament to an industry which often does not advance its image as much as it could. Nonferrous metals production is a high-tech business requiring advanced understanding of thermodynamics and mathematics to make pyrometallurgical, hydrometallurgical, and electrochemical processes feasible. Often these processes must be carried out in extremely hostile environments and the selection of materials to contain and sustain the processes is a tremendous challenge.

In the time period reviewed, the NFMI has managed to significantly improve the quality of our products and dramatically lower the costs of making our metals. This has been accomplished despite the ever-rising price of energy and always within the constraints of the commodity-based economic system which does not allow us to sell our products at prices reflective of true costs. At the same time, this has been done while recapitalizing our operations so that they also meet the requirements set for the environment and for sustainable development in the communities where we work. The contributions of all those who have worked in technology development during this time period truly deserve recognition.


This paper is based on the keynote presentation given on behalf of the Extraction & Processing Division in recognition of the 50th Anniversary of TMS joining AIME. The author gratefully acknowledges the many conversations over the years with members of TMS which contributed input to the paper and, in particular, the specific support and comments from Phil Mackey of Xstrata Nickel and Sam Marcuson of Companhia Vale do Rio Doce.


1. N.J. Themelis, Vuoritellisuus Bergshanteringen, 51 (2) (1993), pp. 90–95.
2. H.H. Kellogg, AIME Centennial Volume, 1871–1971 (New York: AIME, 1971), pp. 147–161.
3. P.J. Mackey and J.K. Brimacombe, Savard/Lee Intern. Symp. on Bath Smelting, ed. J.K. Brimacombe et al. (Warrendale, PA: TMS, 1992), pp. 3–28.
4. N.J. Themelis, JOM, 46 (8) (1994), pp. 51–57.
5. R.M.G.S. Berezowsky et al., JOM, 43 (2) (1991), pp. 9–15.
6. “Death of Mining,” Business Week (17 December 1984).
7. M. King and V. Ramachandran, Encyclopedia of Chemical Technology, 4th Edition, Volume 15, ed. Kirk Othmer (New York: John Wiley and Sons, 1995), pp. 69–113.
8. P.E. Thwaites et al., “System and Method for Furnace Monitoring and Control,” Canadian patent application 2,469,975 (4 June 2004).
9. R.L. Breuning et al., Hydrometallurgy 2003, Volume 1: Leaching and Solution Purification, ed. C.A. Young et al. (Warrendale, PA: TMS, 2003), pp. 729–739.
10. S.G. Galbraith et al., Hydrometallurgy 2003, Volume 1: Leaching and Solution Purification, ed. C.A. Young et al. (Warrendale, PA: TMS, 2003), pp. 941–954.
11. H.R. Watling, Hydrometallurgy, 84 (2006), pp. 81–108.
12. D. Fragomeni et al., Proceedings of the 37th Annual Meeting of The Canadian Mineral Processors (Montreal, ON, Canada: CIM, 2005), pp. 75–98.

Michael G. King retired as the Director of Metallurgical Technology for Xstrata Nickel (formerly Falconbridge Ltd.). Mr. King can be reached at 806 N. Northpoint Drive, Salt Lake City, Utah 84103-3346; e-mail