Process Mineralogy and Geometallurgy

I had lunch yesterday, at Falmouth’s beautiful Indaba on the Beach restaurant, with my former Camborne School of Mines colleague, Dr. Alan Bromley. Alan was an inspiration to me during my time at CSM. He was of a rare breed, a geologist with a keen interest in mineral processing, and I suppose one of the pioneers of the then new discipline of process mineralogy. He gave a seminal lecture in the mid-70s “A geologist looks at mineral processing” which was a call for all mineral processing operations to arm themselves with microscopes and closely examine their feed and product streams, something that was never done during my time at Nchanga, despite its complex suite of copper minerals.

We reminisced on how process mineralogy has evolved since then, with sophisticated automated scanning electron microscopes such as QEM*SEM now commonplace in large operations. In the early 80s, CSM was the proud owner of one of the early image analysers, the monochromatic Quantimet 720, capable of performing linear scans on mineralogical specimens. Such was the power of this machine, that it lured the late Prof. Peter King from Wits University to a sabbatical at CSM, where he worked with Alan on his pioneering research into liberation analysis.

Alan inspired many others at CSM. Dr. Alan Butcher, now with FEI in Australia, a former geology lecturer at CSM, went on to do great work with QEM*SEM at CSIRO, and then Intellection.

Ironically, we met another old colleague in the restaurant, Mike Hallewell, formerly mill superintendent at Wheal Jane tin mine, now with SGS in Cornwall. Mike is now a geometallurgist, a relatively new discipline which has evolved from process mineralogy. Geometallurgy relates to the practice of combining geology or geostatistics with extractive metallurgy, to create a spatially or geologically-based predictive model for mineral processing plants. It is used in the hard rock mining industry for risk management and mitigation during mineral processing plant design. It is also used, to a lesser extent, for production planning in highly variable ore deposits.

Geometallurgy is just one of the themes of Process Mineralogy ’10, which will be held in Cape Town in November. This is looking like it will be a major event, with ALS Mineralogy and IMP Holdings already committed to early sponsorship. One of the keynote speakers will be Dr. Norman Lotter, of Xstrata Process Support, Canada who will present "Process Mineralogy- a History and the Future".

So, if you have an interest in process mineralogy (and all mineral processors should have) then Cape Town’s beautiful Vineyard Hotel is the place to be in November.

St. Just and Geevor Mine

Barbara and I had a Sunday drive out to Land's End today, and stopped for coffee in the old tin mining town of St. Just, almost a ghost town now after the closure of the nearby Geevor Tin Mine in 1990

Geevor is now a museum and as the weather was so bad, we stopped in to experience the mine and mill tour.

I have to say that it was disappointing. Our guide was an old miner, whose knowledge of milling was very rudimentary, and the only piece of equipment in operation for the public was a single shaking table, running in closed circuit with water. 

There are better mining museums in Cornwall, and over the next few months I will be visiting and reporting on these.

Comminution and enhanced mineral liberation

I have been looking at the final programme for Comminution ’10, and one paper from Hacettepe University in Turkey brought back memories of comminution research at CSM and Birmingham in the mid 1980s. In their abstract Ozcan and Benzer state:

"The comminution process is still governed by a large number of factors that influence the liberation of the valuable components in the ore. A better understanding of these basic factors will provide more certainty about the design of equipment in order to achieve the best liberation and energy efficiency.


The aim is to improve our understanding of the influence that breakage and the intensity of breakage has on the particle size distribution and the liberation of the valuable minerals. Liberation enhancement is sought for two main reasons. Firstly, if liberation is achieved without needing to grind particles to fine sizes, less is spent on energy. Secondly, over-grinding is not only costly, but produces fines that tend to interfere with subsequent separation processes thus making the downstream processes both inefficient and more expensive."

Over the past couple of decades great improvements have been made in comminution equipment, control and simulation, but it must never be forgotten that enhanced liberation should also be a major aim. Seventeen years ago, Keith Atkinson and I published a paper in Minerals Engineering (Volume 6 Number 7, 1993) entitled “Some observations on the fracture and liberation of mineral assemblies”. The paper considered the need to research more deeply the mechanisms of the breakage processes in comminution machines, particularly the promotion of intergranular fracture. It was shown that in order to do this control of crack propagation, and the nature and role of grain boundaries, are areas deserving most attention. I think this paper still provides food for thought, and it can be accessed on ScienceDirect.

I am sure that enhanced liberation will be discussed next month in Cape Town and that high-pressure grinding rolls will be debated in this regard. Interestingly, in the latest issue of Minerals Engineering (Volume 23 Issue 5, 2010), Vizcarra et al suggest that breakage devices utilising particle-bed breakage mechanisms (such as HPGR) do not enhance the liberation properties of metalliferous ores as many previous investigations have reported.

Currently around 140 delegates are registered for Comminution '10 and three exhibit booths are still available. One of these (#4) is in a prime location in the coffee/lunch area.

World Cup could cause spike in metal prices

According to an article in The Times (20th March) some of South Africa's largest electricity consumers, including the mining industry, have been asked to reduce their usage during the World Cup to ensure there are no blackouts. The country has a severe electricity shortage and the arrival of an estimated 450,000 football fans is expected to increase strain on the grid.

Xstrata has said that it will move an annual maintenance programme at its energy-intensive ferrochrome smelters to coincide with the World Cup. The mining industry accounts for 15% of South Africa's electricity consumption, and has already experienced rationing from Eskom, the South African power utility.  At the start of 2008 the utility was forced to limit electicity supplies after heavy rain damaged coal stocks. Subsequent blackouts forced several of the country's largest miners, including Anglo American, Anglo Platinum and AngloGold Ashanti to shut down operations for several days. The mines remained rationed for several months, and the drop in production caused metal prices to spike, platinum rising by 24% in subsequent weeks, and ferrochrome doubling, South Africa accounting for nearly three quarters of global production of these metals.

So look out for further spikes in these metal prices if the World Cup leads to further overall shortfalls in electricity supply.

The best ever conference dinner?

We have now organised our travel and accommodation for September’s IMPC in Brisbane. There are no conference dinner details available as yet, but I am sure that the Aussies will have something special planned. Nothing brings people together better than a good conference dinner, and in recent years there have been some fine IMPC events.

In the past, IMPC dinners tended to be dull, formal affairs, with endless speeches from members of the organising committee and local dignitaries. Everything changed in 2003 with the unforgettable evening at Cape Town’s Ratanga Junction, where mineral processors from all around the world danced the night away to South Africa’s hottest singers and musicians.

Cape Town ’03 set the standard that had to be attained or beaten at subsequent IMPCs and Turkey laid on a wonderful event in Istanbul in 2006 with an evening of entertainment which included the country’s number one belly dancer!! A far cry from a dry speech by the mayor in the local town hall!

For sheer spectacle, however, it will be hard to beat the dinner-show, set to the backdrop of the Ancestral Palace, that the XXIVth IMPC provided in 2008 in Beijing. A few photos from this event are shown here, and many more can be viewed on MEI Online.

So, what are your views on the importance of conference dinners, and what were your particular favourites?

Stephen Neethling joins the band of MEI Conference Consultants

We would like to welcome Dr. Stephen Neethling to our elite group of conference consultants.

Stephen is a Senior Lecturer in the Royal School of Mines at Imperial College London. He obtained his PhD on the modelling of Froth Flotation from the University of Manchester, where he also worked for a number of years a lecturer. He obtained his undergraduate degree in Chemical Engineering from the University of Cape Town.

Stephen will be advising us on the organisation of Computational Modelling '11, which will be held in Falmouth, Cornwall next year.