The latest mining research from experts in the industry

Materials World magazine
,
2 Aug 2016

Humans have been exploring and mining for metals since the Stone Age, but that doesn’t mean we’ve perfected the process. Rhiannon Garth Jones looks at some of the latest developments in mining research. 

Dr Ben Williamson, of the Camborne School of Mines, University of Exeter, UK, has been working on a new and inexpensive method to identify porphyry-type copper deposits.

Tell me about your background.

My passion for geology was sparked by my grandfather, who was an independent prospector in the Northwest Territories of Canada. I did a BSc in Geology at Royal Holloway University of London, UK, and then a PhD at Birckbeck University and Royal Holloway on The Petrology of the Velay Granite Complex, Massif Central, France. On completion, I got a job as a drilling controller in the oil industry and spent two interesting years working offshore in Mauritania, and the Congo, and onshore in Yemen. I missed doing research and, fortunately, was given a junior research and technical position at the Natural History Museum, London. During my time there, and at a brief post at the University of Bristol, UK, I carried out research on granite-related mineralisation and was involved in projects to assess the environmental impacts of mining-related activities in Romania and the Ural Mountains of Russia. 

In 2007, I was offered a lectureship in Applied Mineralogy at the Camborne School of Mines, the University of Exeter, where I have been teaching and continuing my research on granites and related mineralisation and mining environmental impacts.

Where does your main area of interest currently lie? 

I am involved in a number of research fields, including environmental aspects of mining-related activities and volcanology. However, my main interest is in porphyry deposits and, specifically, their mechanisms of formation and developing mineralogical and geochemical tools to aid in their discovery.

Tell me about the method you have been working on.

Porphyry copper deposits mainly form within magmatic rocks above subduction zones. The main mineral within such magmatic rocks is plagioclase. From an initial desk study, bringing together data from a large number of magmatic rocks worldwide, we found that there is a chemical difference between plagioclase in magmatic rocks which host porphyry copper deposits from those that are barren. This provided a tool that exploration companies can use to explore for porphyry copper deposits. 

Anglo American then sponsored us to test the method on plagioclase in drill core samples from their new copper porphyry discovery at Los Sulfatos, Chile. The method not only worked very well, but also allowed us to gain new insights into how porphyry deposits form. Importantly, it showed that porphyry magmas appear to undergo sporadic injections of water-rich magmas or watery fluids, which increases their likelihood of producing copper deposits.

It is hard to say whether the plagioclase method is better than others, as there are too many variables. No current methods work well in isolation and, therefore, our method is likely to be one of a suite of tools used by exploration companies to home in on porphyry copper deposits.

What was the impetus? 

Porphyry deposits provide around three quarters of the world's copper and a significant amount of molybdenum and gold. Most major near-surface porphyries have already been found and new deposits are likely to be deeper and more difficult to discover. Any new tools to find porphyry copper deposits are therefore of interest to exploration companies.

Where do you hope to take this research next?

We would like to test the method on other deposits and in a variety of real-life industry exploration scenarios worldwide. In addition, we would like to test other minerals from the magmatic rocks to see if they show similar patterns and can tell us more about the mechanisms of porphyry copper deposit formation.

The exploration and mining industries are currently experiencing a downturn, mostly because of lower commodities prices, and many companies have reduced or withdrawn resources for third party research. However, an increasing world population and continued growth in some of the world's largest economies, albeit at a relatively slow rate, means most people agree that long-term demand for copper will grow. The development of new methods to find copper deposits may be extremely important in meeting this demand.

David Clarke, Professor of Materials at Harvard University, USA, devised a method to separate rare earth metals using bacteria and solutions with pH no lower than hydrochloric acid, potentially allowing furthered extraction in both an environmentally friendly and industry-beating standard.

Tell me about your background.

I've been fortunate to have carried out research in a wide variety of materials over the years at universities in the USA (MIT, Berkeley and now Harvard), at NPL in Teddington, UK, as well as companies (such as IBM Research and Rockwell Science Center), ranging from ceramics, composites, semiconductors and elastomers. I was one of the first graduates in Materials Science at the University of Sussex, UK, and obtained a PhD in Physics from the University of Cambridge. 

Two factors attracted me to this area and biogenic processing in general. One is the growing interest from our students, and society as a whole, to develop less wasteful processes that also have less impact on the environment. The second is to start using the tools and rapid advances in microbiology to affect materials processing, so that our students have a broader education and hopefully learn some micro-biology.

Where does your main area of interest currently lie?

Partly in biogenic processing, partly in high-temperature materials, such as thermal barrier coatings, and partly in engineering with elastomers.

Tell me about the method you have been working on.

Originally, we were seeking to determine if there were microbes that would specifically interact biologically with the rare earths in solution, and then characterise their interactions, whether with proteins, DNA or some other agent. However, what we discovered is that many bacteria interacted physical-chemically, by binding the rare earth ions to molecules and groups on the surface of the bacteria. Furthermore, the binding depended on the solution pH and the atomic number of the rare earth ions, so we could adsorb all the rare earths at close to a neutral pH and then selectively de-sorb specific rare-earths as a function of pH.

The selectivity of our absorption-delution method is comparable to existing solvent extraction methods but uses more benign chemicals and so is expected to have less environmental impact than current methods.

What was the impetus?

Although rare earth elements are not really rare, they are essential for many technologies, ranging from permanent magnets, solid-state lighting and motors and some battery chemistries. For several years, mines closed around the world, the price of rare earths skyrocketed and there was a real concern that their supply was being curtailed. Market adjustments, decreased demand associated with decline in global economy and closure of some of the most highly polluting mines in China, have all resulted in price drops and there is now less concern about the immediate availability of these important elements. However, the cost of separating the individual rare earths from one another, as well as the environmental cost, remains a major factor in the price. If our results can be reproduced on an industrial scale, our work could decrease the real financial and environmental cost of producing rare earth elements, and thereby increase their use in future technologies.

Where do you hope to take this research next? 

We wish to explore scaling up the process, as well as obtain a clearer understanding of which surface groups on the bacteria bind to which different rare earth ions. This basic research would be a stepping stone to identifying a more refined model for the binding and possibly the identification of bacteria with even greater separation specificity for individual rare earths.

Frank Bruno, Associate Research Professor at the University of South Australia is leading a research project on cutting edge molten salt technology that will significantly reduce energy and water usage and, therefore, the cost of mineral processing using molten salts.

Tell me about your background.

I have a degree in Mechanical Engineering from the University of Adelaide, Australia, and a PhD in Mechanical Engineering from the University of South Australia. I have been involved in research in the sustainable energy area for more than 20 years, including thermal storage, low energy buildings, air conditioning, refrigeration and solar thermal. 

I have always been interested in energy as well as sustainability and was particularly interested in thermal storage, as it is one of the lowest cost energy storage technologies. I believe that at some time in the future it will be an important technology for integration with cheap renewable energy generation.

Where does your main area of interest currently lie? 

Over the past four years, I have been heavily involved in research on thermal energy storage using phase change materials for concentrating solar power plants.

Tell me about the method you have been working on.

Until now, I have been working on phase change materials comprising of salt mixtures. This research has enabled me to gain extensive knowledge on the behaviour and handling issues of molten salts at temperatures up to 700°C.

The new research will involve working with molten salts at temperatures above 850°C, developing techniques for separation of mixtures of highly reactive molten salts, as well as identifying suitable containment materials and transporting techniques.

What was the impetus? 

The specific research programme will be to develop a minerals processing circuit to leach, extract and purify metals from silicate minerals in a solely molten salt environment, without the need for subsequent aqueous processing. The Oxley Potassium Project, at the University of South Australia, will be the basis of the research targeting potassium from potassium feldspar, an alkali metal silicate mineral (KAlSi3O8).

Centrex Metals has already developed a process route for its Oxley potassium deposit that is a mix of molten salt processing for conversion of potassium to a leachable form, followed by extraction and purification in a low-temperature aqueous circuit. The process route is focused on the production of high value specialty fertilisers such as potassium nitrate or potassium sulphate.

If the new research programme is successful, the ability to undertake all processing steps in a molten salt environment could significantly lower processing energy, water and capital costs.

Where do you hope to take this research next? 

The knowledge developed in relation to the mechanical and materials engineering issues involved with transferring and separating solids from highly-reactive molten salts at high temperatures can be adopted in other applications such as solar power plants, molten salt reactors, high-temperature thermal energy storage, glass optical property modification and refining for other minerals.

To view a video detailing the process from Harvard University, download the Materials World App.