Monday, 20 October 2025

Prof. John A. Herbst: 1942-2025

There was sad news from USA this weekend of the death, on Friday, of Prof. John Herbst, at the age of 83. Prof. Herbst was an Adjunct Professor of Metallurgical Engineering in the Department of Metallurgical Engineering at the University of Utah
He gained his PhD from the University of California, Berkeley, under the supervision of Prof. Douglas Fuerstenau and as a graduate student at the University became one of the pioneers in applying population balance models to ball mill comminution.
His main focus was on modelling, simulation, optimisation and control of grinding (comminution) and flotation circuits. He provided a bridge between industry and academia and his focus on process modelling (especially in comminution and flotation) set him apart.
He served as Chair of the Department of Metallurgy and Metallurgical Engineering at the University of Utah from 1977 to 1986 and he founded the USBM Generic Mineral Technology Center for Comminution at Utah in 1982 and served as its director until 1988. 

One of his well-known students, Dr. Osvaldo Bascur, said of his supervisor "John was an outstanding Professor.  His scientific approach to mineral processing using particulate systems was very defined. His class notes were very well organised and his examples very well chosen.  He provided outstanding coaching, mentoring and support for his students at the University of Utah".

Osvaldo Bascur (right) with John Herbst and Prof. & Mrs. Kal Sastry in Cape Town, 2003

John co-founded the company Control International Inc. in 1986 (a joint venture with ARMCO) to apply modelling and control in mineral processing plants. He sold his part of the business in 1996 and formed J.A. Herbst & Associates in Salt Lake City. The overall purpose was to support companies using advanced technology in their processing operations. They developed a dynamic flowsheet simulator, a soft- sensor line for comminution, and an image analysis system for coarse size particles in grinding systems.

From 2000-2016 John was with Metso Minerals, becoming Chief Scientist and Manager of Technology Development before becoming the Robert E. Murray Chair and Professor of Mining Engineering at West Virginia University, and then Adjunct Professor at the University of Utah.

Prof. Herbst received multiple awards from professional societies and he was inducted into the U.S. National Academy of Engineering in 1992 in recognition of his contributions.

In 1995 he was the principal organiser and President of the XIXth IMPC/SME Conference and Exhibition held in San Francisco, at which his former supervisor, Prof. Douglas Fuerstenau became the first person to be awarded the IMPC Lifetime Achievement Award. John was too ill to attend the IMPC in Washington last year, where he was also awarded the Lifetime Achievement Award.

San Francisco 1995 with Doug Fuerstenau and Eric Forssberg

I first met John and his wife Cindy at the IMPC in Sydney in 1993 and in 1998 John and Cindy played very active parts in MEI's Minerals Engineering '98 in Edinburgh.

With John and Cindy and Gordon Agar in Sydney, 1993
John and Cindy with Peter Radziszewski and Barbara Wills, Edinburgh 1998
John and Cindy with conference delegates at the Glenturret whisky distillery, 1998

Since then we caught up at IMPCs in Cape Town and Quebec.

With Doug Fuerstenau and Peter King, Cape Town 2003
Cindy and John with Amanda Wills, Romke Kuyvenhoven and Osvaldo Bascur, Quebec 2016

Prof. John Herbst was a giant in the mineral processing community. He will be sorely missed by his friends around the world and we extend our condolences to his wife Cindy and all his family.

Friday, 17 October 2025

October Cornish Mining Sundowner: a chance to thank Gravity Mining

 A good sundowner last night at Falmouth's Chain Locker, probably the last outdoors for several months.

Camborne School of Mines students

We are pleased that the Cornwall Mining and Georesources Alliance (CMGA) is bringing in new faces by promotion of the sundowners. The CMGA brings together world class expertise to support the global mining and geothermal industries, its members being active in the Green Metals transition and modern responsible mining worldwide. 

David Mildren is a CMGA Director, and is a Director of Cornish company Gravity Mining, manufacturer of the Multi Gravity Separators (MGS), which will play a big part in the future gravity circuit at the South Crofty tin mine. At the August sundowner I suggested to David that the company might sponsor next year's Physical Separation '26 in Cape Town, and we are delighted to announce that they have agreed, and will be promoting their range of MGS machines at the event, including their latest offering the huge C910 MGS (posting of October 13th). It was good to thank David and his brother and fellow Director, Treve, for their support next April.

With Dave and Treve Mildren

The next sundowner will be at the Chain Locker on Thursday November 20th, from 5.30pm.

Monday, 13 October 2025

Back to the Future: The Resurgence of Physical Separations

It’s remarkable to consider that in the mid-19th century, global annual copper production was only about 60,000 tonnes, compared with roughly 24 million tonnes today. In the early 19th century, Cornwall and Devon in the UK were the world’s leading copper producers. By 1850, however, Cornish mines were in decline. Although still significant by 1860, Chile had overtaken them as the dominant supplier, with the USA emerging as a major producer and eventually surpassing Chile by the late 19th century.

The ores from these early producers were exceptionally high grade, typically between 5-15% Cu. Any necessary upgrading could be achieved by simple hand sorting or by basic ore-dressing methods such as jigs, buddles, and round frames, techniques commonly employed in Cornish tin mining.

Remains of buddles at the Botallack mines, Cornwall

Chile’s copper boom (1840s-1870s) relied on rich oxide ores, malachite, azurite, and chrysocolla, and production peaked mid-century. By the 1880s and 1890s, however, many of these oxide deposits were exhausted. The remaining resources were low-grade sulfides (mainly chalcopyrite) hosted in large porphyry systems. With 19th-century technology, these were uneconomic: grades were often below 2% Cu, far too low for traditional methods. Consequently, Chile lost its leading position to the United States (notably Michigan and later Butte, Montana) by the late 1800s.

As global demand for copper surged, driven by the electrification of society, the invention of froth flotation around 1905 revolutionised low-grade sulfide mining. Finely disseminated chalcopyrite could now be concentrated to 20-30% Cu, making vast porphyry deposits commercially viable. This technological breakthrough resolved what had seemed an existential problem for the mining industry, allowing Chile to once again supply growing industrial and electrical demand for copper - a position it retains to this day.

From the early 20th century onward, flotation dominated mineral processing, relegating gravity separation to a minor role. It remained vital, however, for certain ores such as tin, and innovations like the Wilfley Shaking Table, still widely used, rendered older devices like Frue vanners obsolete. A resurgence came in the 1970s with the advent of high-capacity gravity separators such as Reichert Cones and spirals, and more importantly, enhanced gravity machines including the Knelson and Falcon concentrators.

Magnetic separation has been part of mineral processing since the late 19th century, but the 20th century brought major advances that transformed it from a niche technique into a standard tool for ore beneficiation. The development of stronger permanent magnet materials enabled compact, reliable drum separators without relying solely on electromagnets. Applications expanded beyond magnetite to paramagnetic iron ores such as hematite and limonite, thanks to finer grinding and high-intensity magnetic separation (HIMS). Further progress in the 1960s and 1970s saw the advent of wet high-intensity magnetic separation (WHIMS) for slimes and finely disseminated ores.

One of the most significant WHIMS developments was the Jones Separator, the first truly practical, high-capacity machine of its kind. 

The Jones Separator (a) Plan View  b (top view)

The concept originated with Dr. George Jones, head of engineering at the Camborne School of Mines, who in the late 1950s and early 1960s sought ways to apply strong magnetic fields to weakly magnetic minerals like hematite and wolframite. His innovative rotating carousel design became the foundation of the Jones Separator. Assisting him was a talented mining student, who worked on the prototype for his final-year project. His name was Richard Mozley.

Richard Mozley went on to become one of Cornwall’s most prolific inventors, pioneering hydrocyclones for ultrafine desliming and developing a range of commercial gravity separators. His most renowned invention was the Multi-Gravity Separator (MGS), designed to compete with other enhanced gravity machines such as the Knelson, Falcon, and Kelsey Jig.

Richard Mozley died in 1995, but he would surely have been astonished by the latest evolution of his creation: the C910 MGS, the world’s largest gravity concentrator. Designed specifically for bulk commodities such as iron ore and chromite, it enables the recovery of ultrafine minerals often lost to tailings.

Gravity Mining Directors Colin Colino, Treve Mildren and David Mildren
at the launch of the C910 MGS earlier this year

We will hear more about this remarkable device at Physical Separation ’26, to be held in Cape Town next April. Dr. Kristian Waters, Associate Professor and Chair of the Department of Mining and Materials Engineering at McGill University, Canada, will deliver a keynote lecture highlighting the renewed importance of physical separations. Enhanced gravity concentrators, along with emerging technologies such as the Reflux Classifier and the new MGS, are at the forefront of this revival. This trend aligns with the industry’s growing focus on responsible energy usage, particularly efforts to reduce comminution energy by rejecting barren particles before grinding, through ore sorting.

Kristian will illustrate how sensor-based ore sorting effectively revives the concept of the human sorter of a century ago, marking a true resurgence in the value of physical separations. It is fitting that this conference is supported by two global leaders in this field: TOMRA and Steinert.

If you would like to submit an abstract to Physical Separation '26, or to Mineral Processing '26 which follows it, the deadline for abstracts is October 31st.

#PhysicalSeparation26

Thursday, 9 October 2025

Memories of Process Systems '05

Immediately following Computational Modelling '05 at Cape Town's Mount Nelson Hotel (Monday's posting) was a 2-day conference Process Systems in the Metallurgical Industries '05, organised by MEI in consultation with Chris Aldrich from the University of Stellenbosch, and sponsored by Limn: the Flowsheet Processor.

At the Cape Town Waterfront: Peter Hand, South African agent for Limn, Barry Wills of MEI,
Dave Wiseman of Limn, the sponsor of the event, and conference consultant Chris Aldrich
The conference was attended by 30 delegates and Chris Aldrich provided a brief report.  Selected papers from the conference can be found in Volume 19 Number 11 of Minerals Engineering, and a few photos taken at the event are shown below:

Monday, 6 October 2025

Memories of Computational Modelling '05

November is fast approaching and Flotation '25 is now only 6 weeks away. This will be the biggest conference in MEI's history, but 20 years ago in November we held three small conferences in Cape Town. They were held at the Mount Nelson Hotel, a couple of years before we discovered the Vineyard Hotel.

The first of the three events was Computational Modelling '05, the first of what was to become a series of seven conferences, initially suggested by Jan Cilliers, who at the time was a lecturer at the University of Manchester and is now Professor of Mineral Processing at Imperial College, London.  

We ran the conference in consultation with Jan, and it was sponsored by DEM Solutions.  There were 40 delegates, some of whom can be seen in the photos below.

With Jan Cilliers and John Favier of DEM Solutions

Selected papers from the conference can be found in Volume 19 Number 10 of Minerals Engineering.

Thursday, 2 October 2025

AECI Mining Chemicals Strengthens Partnership with MEI Conferences

AECI Mining Chemicals, a division of AECI Ltd, is part of a diversified group of 16 companies and employs 400 people. In addition to South Africa, they are involved in Botswana, Namibia, Zambia, Zimbabwe and the DRC. The next target markets are in Ghana, Morocco and Tanzania as well as Australasia and South America. 

AECI Mining Chemicals adds value in the beneficiation of primarily PGMs, diamonds, coal, gold, uranium and base metal ores. Most of their products are used in the froth flotation and tailings treatment sectors of the mining industry. The portfolio includes specialty thiol-based collectors, mineral froth formation chemicals, unwanted gangue mineral depressants, polyacrylamide thickening polymers and tailings polymeric rheology modifiers. 

AECI Mining Chemicals has the largest mining chemicals manufacturing facility on a single site in the southern hemisphere and a state-of-the-art R&D centre where world-class specialists deliver innovative solutions not only for today’s mineral extraction challenges but also for mining of the future. 

The company has become a valued regular sponsor of MEI’s Flotation conferences, first joining us at the online Flotation ’21 event during the pandemic. This followed a long-standing relationship with Senmin, which now forms part of AECI’s Mining Solutions pillar.

With the return to in-person events at Flotation ’23, Shani Engelbrecht, Global Portfolio Manager, shared: "A big shout-out to MEI Conferences for creating such a stimulating environment! Flotation ’23 has been a truly enriching experience - I left with my mind challenged and heart full."

MEI's Jon Wills with the AECI team at Flotation '23

The impact was immediate: AECI Mining Chemicals signed on as a sponsor for Flotation ’25, Process Mineralogy ’24, and Critical Minerals ’24. We are now delighted to welcome them back once again as sponsors of Process Mineralogy ’26 and Critical Minerals ’26 in Cape Town.

#ProcessMineralogy26
#CriticalMinerals26