Innovations in the processing of difficult and low grade gold ores

While declining grades has always been an ever-present risk for all metallurgical commodities, it has become particularly severe for precious metals where average precious grades are trending towards 1 gram per tonne, or lower. Exploration success in finding long-life, medium grade deposits has been poor with most recent finds being low grade, complex ores. New precious metal resources are more difficult to process due to a host of factors such as mineral refractoriness, high sulfur ores, gold ores with high levels of copper, high silver-gold ores , carbonaceous gold ores, clay-rich ores and gold ores with high levels of reactive sulfides, or a combination of these factors. Moreover, the mining, comminution and processing of low grade gold ores with the concomitant waste generation and reagent consumption, in the context of declining commodity prices and rapidly increasing energy costs, require an overall rethink of both current operations and the feasible extraction of future mineral resources.

Jacques Eksteen at a previous Falmouth conference

Some recent developments in the areas of pre-concentration, flotation, leaching and competitive adsorption within the context of difficult and low grade gold ores will be reviewed in a keynote lecture by Prof. Jacques Eksteen at Precious Metals '15 in Falmouth next May.

Jacques Eksteen is the manager of the Gold Processing Technology Group at the Western Australian School of Mines, Curtin University and is the project manager of the AMIRA P420E project on “Environmentally responsible gold ore processing” which is supported by 14 industry sponsors. He was the Group Consulting Metallurgist for Lonmin Plc in Smelting and Refining from mid-2007, and was appointed as professor and chair: extractive metallurgy at Curtin University in February 2012. He has been a regular contributor to MEI's Precious Metals conferences, and also to the Nickel Processing events which run back to back with them.

Polzeath to Padstow

A very pleasant day out today, walking from Polzeath on the north Cornwall coast, to Padstow.

Polzeath

This is an easy 4 mile walk as the coast path follows the dunes on the estuary of the River Camel, passing by the church of St. Enodoc, where lie the remains of the poet John Betjamin (see posting of 27th January 2013).

Approaching the Camel Estuary

Camel Estuary

Walking the dunes

At Rock, we took the ferry across the Camel to a very busy Padstow. After a quick pasty lunch we left the crowds behind and returned to Polzeath, which is only a 40 mile drive from Falmouth.

Padstow Harbour

More Cornish Walks
More on Cornwall

Process Mineralogy '14 programme published

The provisional programme for Process Mineralogy '14, which will be held in Cape Town in November, has now been published.

The opening session of Process Mineralogy '14

This is very provisional at this stage, and as the programme evolves updates will be posted on the conference website (Twitter #ProcessMineralogy14). If you like the programme, and feel that you can contribute, please send a short abstract as soon as possible.

We are also pleased to announce a new dinner venue. The conference dinner will be held at moyo Kirstenbosch, at the foot of Table Mountain in the beautiful Kirstenbosch Botanical Gardens.

Kirstenbosch Gardens

 

Is South Africa's precious metals era drawing to a close?

Last year I reported on South Africa's decline as a major gold producer (posting of 25th September 2013), from being the number 1 producer a decade ago to now number 6 in the world rankings.

Is platinum, of which South Africa has 90% of the world’s deposits, set to go the same way as the country's ageing, deep gold mines? This is the question asked in African Mining Brief, reporting on a recent University of Cape Town Graduate School of Business round table.

The current mining strike, which ends today, is the latest challenge to beleaguer South Africa's battered and once hugely profitable platinum industry. After 2008, South Africa, the world’s largest producer of platinum, was hard-hit by the global recession and erosion of the market for platinum and its by-product, rhodium. Making a recovery, it has since been knocked by a surge in the scrap supply and the recycling of platinum by other producers, as well as by palladium, produced largely by Russia, and used as a platinum substitute catalyst notably in the auto industry. The current platinum strike has been the longest and most expensive strike in South Africa’s mining history, with some 70,000 miners now returning to work after downing tools on 23 January 2014, costing mining firms R19 billion in lost revenue, miners approximately R8.8 billion in wages and the country's GDP a drop of 0.6% in the first quarter.

Platinum itself is extremely labour-intensive to mine in deep shafts and complex to process and the panel forecast that opencast mines, which are low in investment but high in environmental impact, and mechanisation, lie ahead, a shift away from traditional labour-intensive shaft mining.

All in all the future looks bleak for South African mining, vindicating our decision to move MEI's Precious Metals '15 to Falmouth, close to the rapidly evolving European precious metals producers.

Young Persons' Awards

It is always good to hear of young people in our industry being awarded for their endeavours, so I was pleased to receive an email recently from Prof. Dee Bradshaw of JKMRC, Australia, who is currently on sabbatical at Hacettepe University, Turkey. Dee is also one of MEI's two consultants for Flotation '15. She sent me news of two recent alumni from the Sustainable Minerals Institute at the University of Queensland (UQ) who have both published in Minerals Engineering and who have been rewarded with recognition from their University for outstanding theses. She "thoroughly expects both of them to be leaders in the field in the future".

The two young researchers each won a prestigious Dean’s Award for Research Higher Degree Excellence 2013. The award, given by the Dean of the UQ Graduate School, gives formal recognition to outstanding PhD and MPhil graduates who have demonstrated excellence in a research higher degree and who have been commended by advisers and independent examiners for substantial contribution to their field of research.

Dr. Wenying Lui's PhD thesis was "A quantitative risk-based approach for improving water quality management in the minerals industry: flotation as an example" Her advisers were Prof. Chris Moran and Dr. Sue Vink.

Wenying has published 5 papers in high-ranking international journals and has also published several conference papers, having presented her work at Procemin 2011 in Chile and the SME Annual Meeting in USA in 2012. She is currently working as a postdoctoral research fellow at the University of British Columbia in Canada.

Wenying (left) with fellow PhD students and staff, 2011

Gerson Sandoval-Zambrano‘s PhD project was entitled "Development of a novel strategy to estimate flotation recovery as a function of particle size and mineral liberation." Gerson was supervised by Dr. Elaine Wightman, Prof. Dee Bradshaw and Dr. Gonzalo Montes-Atenas.

After finishing his undergraduate degree at the University of Concepcion, Chile and gaining some relevant industrial experience in Chile, Gerson joined the JKMRC, Sustainable Minerals Institute (SMI) in 2009 as a PhD candidate. The aim of his research was to develop a novel methodology to predict the efficiency of separating valuable minerals from waste based on the characteristics of individual particles. The outcomes from his work have the potential to reduce the cost and time typically associated with conducting the detailed analysis required to develop a particle property based model of a mineral processing circuit. 

During his candidature Gerson wrote four papers, one of which was published in Minerals Engineering. Two of his papers were published in the peer-reviewed conference proceedings from Procemin 2011 in Chile, which he attended and presented his work. Gerson also presented his work at Flotation '11 and Flotation '13 in Cape Town. This led him to win the SMI Student Publishing award in 2011. In 2012 Gerson was the 23rd winner of the Ian Morley Prize which acknowledges the best overall performance and achievements as a postgraduate student at the JKMRC. He is currently working as a senior engineer at Aminpro, Santiago, Chile.

Gerson´s farewell from Brisbane (front: Gerson, Jocelyn Quinteros, Dr. Cathy Evans,
Prof. Dee Bradshaw. Back: Dr. Elaine Wightman, Prof. N.W. Johnson, Mrs Johnson)

Congratulations Wenying and Gerson, I am sure we will hear much more of you both in the future.

Cornish Mining Sundowner- June

The sun shone brightly last week for the SRCR '14 sundowner, and has continued to do so all week, so it was a very warm evening at the Chain Locker pub in Falmouth for today's Cornish Mining Sundowner. A disappointingly low turnout, however, probably due to tonight's vital World Cup match between England and Uruguay, which I rushed home to watch (even more disappointing!).

Good though to catch up with a few mineral processors, including Bentley Orchard of Weir Minerals, and Jim Turner, who graduated from CSM in1984 and is now based in nearby Penryn as a senior mineral processing engineer with Micon International.

With Bentley Orchard, Steve Wilson and Jim Turner

Also in attendance were Steve Wilson, tailings backfill designer with Paterson & Cooke, and his colleague Paul Ainsworth, who graduated in the last batch of mineral processors from CSM in 2006.

Paul Ainsworth and girlfriend Charlotte with Steve Wilson

The next Sundowner will be held on Thursday July 24th, and as always there is an open invitation to anyone who has any connection with the minerals industry to join us at the Chain Locker.