Monday, 22 October 2018

Welcoming two new sponsors for Physical Separation '19: TOMRA and Outotec

We are pleased to announce that Outotec is to sponsor an MEI Physical Separation conference for the first time. The giant international company has regularly supported MEI Conferences, and is a current sponsor for next year's Flotation '19.
TOMRA Sorting Solutions is sponsoring the Physical Separation series for the 4th time. TOMRA, like our other ore sorting sponsor Steinert, is a world leader in automated ore sorting, a technology which is increasing in importance as a means of reducing energy and water requirements in mineral processing flowsheets (see also posting of 22nd July 2018). Only last month TOMRA announced the introduction of a large new X-ray sorter (MEI Online).
It is great to have these two important companies involved in Physical Separation '19 next year, but it was sad to hear last week that Wolf Minerals, who had agreed to sponsor the conference only a few weeks ago (posting of 1st October) has had to close its Drakelands tungsten-tin mine in Devon, and Wolf Minerals (UK) has ceased trading. So unfortunately there will be no post-conference tour of the mine at Hemerdon, as previously announced.
The latest updates on Physical Separation '19 can be found at #PhysicalSeparation19.
Current Physical Separation '19 sponsors
Twitter @barrywills

Friday, 19 October 2018

AusIMM Complex Orebodies 2018: Register Now

MEI are pleased to be media sponsors for the AusIMM's Complex Orebodies 2018 conference in Brisbane next month. The event will provide delegates with a clear understanding of the nature of complexities facing future orebodies, address complexity across the mining value chain and share practical solutions you can apply to your operation. Below is the latest information on the conference.

%%First name%%, see the full program and topics selected for this year.

AusIMM Conference


Hi Everyone,

We are excited to announce the Complex Orebodies conference program! Meet and network with industry peers from CSIRO, BHP, ALS Metallurgy, CRC Ore, Jaguar Mining, Glencore Technology and more.

Some of the program highlights include:
  • Complexity and finding a way to bridge the insight/wisdom of bean counters and story tellers
  • Complex Orebodies and future mineral supply
  • Pilar Gold Mine: Challenges to consider with a complex orebody in the Iron Quadrangle, Brazil
  • Complex Mineralogy but Higher Grade Than Many Ore Bodies
  • Putting the "GEO" back in front of GEOmetallurgy: Importance of early implementation of quantitative mineral system characterisation, classification and modelling

Gain insight from case studies of existing complex orebodies, analysis of the future technical, social, political and environmental landscapes as it affects mining and innovative extraction approaches.

Join us in Brisbane on 19-21 November 2018.

Drakelands Mine, the hot topic at the October Mining Sundowner

Another good turnout last night in Falmouth, for the last of this year's sundowners at the Chain Locker pub.
We were pleased to welcome Mark and Karen Wolle to their first sundowner. Mark graduated from Camborne School of Mines in 1978, and has his own company in South Wales, E3 Recycling Ltd, which recovers copper and precious metals from WEEE using mineral processing techniques. He has two shaking tables manufactured by Physical Separation '19 sponsor Holman-Wilfley Ltd, who also provided the shaking tables for Wolf Minerals' ill-fated Drakelands tungsten-tin mine just across the border in Devon.
With Mark Wolle and Holman-Wilfley's Dave Goldburn
The talk last night was dominated by tungsten. Last week I was in China, which has the largest reserves and production of tungsten in the world, with the country's annual tungsten production of 64,000 being equivalent to over 83% of the global production. Ironically while I was away, Drakelands, near Plymouth in Devon, was forced to close down. Only a month ago Wolf had agreed to sponsor Physical Separation '19 and to provide delegates with a mine visit (posting of 1st October), which unfortunately will now not happen.
The ill-fated mine lost £100 million in just three years because its processing plant failed to deal with the early difficult ore and the fall of global prices saddling Wolf Minerals (UK) with enormous debts.
There had been fears that Drakelands could close as early as 2016, and so when Wolf Minerals (UK) Ltd finally went into administration on October 10, it seemed like the inevitable conclusion to the venture.
Ironically, world wide tungsten prices had been rising in the 18 months before the mine closed, and recovery levels had improved as the processing plant began to deal with the deeper granitic rock, rather than the shallower fine-grained weathered deposits. There are hopes that the mine could be saved but it would need huge investment into a processing plant which has never hit targets. The open-pit operation might attract potential new operators as it has lots of valuable ore and infrastructure already in place. European tungsten mining firms could potentially take control of the mine, one of the largest tungsten reserves outside of China. There are tungsten mines in Austria, Portugal and Spain that might have a future interest in Drakelands.
Twitter @barrywills

Wednesday, 17 October 2018

ALTA 2019

MEI have long been media partners for the ALTA series of conferences, one of the world’s premier annual metallurgical events, now in its 24th year, and are pleased to be involved once again in 2019.

Please read on for the latest update from ALTA 2019...

ALTA 2019 is a world-class annual metallurgical conference now in its 24th year, and a leading platform for innovation.  The emphasis of the program is practical and the themes running through the conference are the various aspects of technology and project development.  We are pleased to partner with CSIRO Minerals for In Situ Recovery and Curtin Gold Technology Group for Gold-PM.  

Call for Papers
ALTA conferences are well-known for providing exceptional opportunities for the industry to share ideas, innovations, technologies and projects.
  • Presenters receive 50% off registration fees.
  • Sole consultant presenters receive 75% off registration fees.
  • Submit your abstract early to secure your place in the program. 

Conference Sessions
  • Nickel-Cobalt-Copper including Pressure Acid Leaching Forum & Panel
  • Uranium-REE including Developments in IX Forum & Panel
  • Gold-PM including Fit-for-Purpose Leaching Systems Forum & Panel
  • Lithium Processing including Novel Lithium Processes Forum & Panel
  • In Situ Recovery including Enhancing ISR Permeability Forum & Panel

Short Courses
  • Treatment of Nickel-Cobalt Laterites
  • Copper SX/EW Basic Principles and Detailed Plant Design
  • Heap Leaching & its Application to Copper, Gold, Uranium & Nickel Ores

Questions about the conference? FAQs
What do people say about ALTA? Testimonials
Read about ALTA 2018

Thank you to our Partners and Co-Sponsors

Free Metallurgical Library
The ALTA Free Library includes proceedings from 1995-2016 Nickel-Cobalt-Copper, Uranium-REE and Gold-PM conferences (1350+ papers). A selection of ALTA 2018 and ALTA 2017 papers is also available. The library is expanded regularly, providing a valuable ongoing resource to the industry.

It's official: Prof TC Rao is the "Father of Indian Minerals Engineering"

I have known Prof. Tadimety Chakrapani (TC) Rao for almost 30 years, ever since, in his capacity as Head of the Department of Fuel and Mineral Engineering at the Indian School of Mines, he invited me to Dhanbad in 1989 to present a course of lectures. Even then I was aware of his reputation and of his early pioneering work on modelling, particularly of hydrocyclones, with Prof. Alban Lynch at the JKMRC in Australia.
In Dhanbad in 1989 with TC (centre) and P.R. Sinha
We have kept in touch since then and he was in Cornwall in 1991 for Reagents '91.
TC in Cornwall, 1991, with Dr. M. Prasad, Prof. Shouci Lu and Prof. T. Wakamatsu
Our last meeting was at the IMPC in New Delhi in 2012, where the chairman of his keynote lecture introduced him as "the Father of Indian Mineral Processing". In 2014 it was my privilege to interview him for the MEI Blog (posting of 16th July 2014).
New Delhi 2012
Now I am pleased to report that during the inaugural function of the XVII International Seminar on Mineral Processing Technology (MPT-2018) on 10th October 2018, Prof. Rao was conferred the honour of "Father of (Indian) Mineral Engineering". The citations read "In recognition and appreciation of immense contributions to the mineral and coal processing education, research and industry in an illustrious career spanning three decades, IIT(ISM) Dhanbad & IIME are honoured in conferring the award of “Father of (Indian) Mineral Engineering” on Professor Tadimety Chakrapani Rao".
Congratulations TC on behalf of us all at MEI.
Twitter @barrywills

Monday, 15 October 2018

A brief but enlightening visit to China's Central South University

Central South University (CSU) in Changsha, China, has around 55,000 students and 20,000 staff and is in the top 20 of 2800 universities in China. There are 38 universities in China with mineral processing departments, and CSU, which specialises in non-ferrous metals, is ranked number 1, and is the largest, with 110 staff, 1000 undergraduate students and 500 post grads. It was recently ranked number 2 in the world in the ShanghaiRanking's Global Rankings for 2018. Around 40% of the mineral processing graduates stay on for post-graduate work, and roughly 20% go into industry or to Institutes.

Despite its unwelcoming austere building and dreary corridors, the Department of Mineral Processing and Bioengineering has some outstanding staff and young researchers, performing cutting edge research in mainstream and innovative mineral processing. All but three are from China; Mohammed Kabashi graduated from the Omdurman Islamic University in Sudan, and came to Changsha a month ago as a lecturer in mineral processing and is researching for PhD on the processing of tailings. Happy Mulenga, a graduate of the Copperbelt University in Zambia, has been at CSU for one year on the MSc mineral processing course, and researching on new reagents for flotation with Prof. Wei Sun. Sultan Ahmed Khoso is a lecturer in the Mehran University of Engineering and Technology in Pakistan, and is at CSU working for a PhD on the flotation of sulphides.
With Happy, Sultan and Mohammed
I spent four days at CSU last week, having kindly been invited to present two short seminars, and to be honoured in a ceremony to confer on me Honorary Professorship of the University. The photo below was taken after the ceremony with some of the mineral processing researchers.  On my left is Prof. Tao Jiang, Dean of the School of Minerals Processing and Bioengineering, and on the right Prof. Xuehong Zhu, Vice-President of the University and QingLyu Liu, Deputy Head of the Human Resources Department. Previous mineral processing appointments to this position have been to Prof. Ponisseril Somasunduran of Colombia University, New York, Prof. Jan Miller, of the University of Utah, and Prof. Roe-Hoan Yoon, of Virginia Technical University, all three recipients of the IMPC Lifetime Achievement Award.
I spent some time talking to leading researchers and in all cases was immensely impressed by their dedication, enthusiasm and amazing work ethic- there doesn't appear to be much time for outside interests if you are a researcher at CSU!
The tireless Dr. Zhiyong Gao arranged and hosted every minute of my visit, including dining with me each day at lunch and dinner, and even spending time to show me the city of Changsha, the capital of Hunan Province, with over 7 million inhabitants.
Dinner with Zhiyong..... the food district of the CSU Campus
The old city....
.....and the new
The EV revolution is happening in Changsha. All the ubiquitous scooters are electric,
and are very quiet, accounting for around 70% of the road traffic accidents in the city
Zhiyong is a fine ambassador for the department and CSU obviously recognises this, as he now represents the department overseas, his first outing being to the IMPC in Quebec two years ago. Last year he presented a paper at Flotation '17 in Cape Town, which was recently published in Minerals Engineering, his 7th to be published in this journal, and last month he was presenting at the IMPC in Moscow. He is an outstanding researcher in one of the main thrusts of the department, flotation chemistry, in the team led by Prof. Yuehua Hu, who I unfortunately missed as he was away in Beijing. Zhiyong's 2015 paper on scheelite flotation is the 6th highest cited paper ever in Minerals Engineering, a notable achievement that he must be proud of. I feel sure that he is a person destined for great things in our profession.
Dr. Haisheng Han and Dr. Yanhong Wang have both spent time at Australia's University of Queensland.
Haisheng and Yanhong
Haisheng is working on the design of new collectors and using mixtures of metal ions and collectors for the flotation of oxide minerals. New collectors for scheelite are now being used at the Shi-zhu yan mine, China's biggest polymetallic deposit, separating scheelite and wolframite from fluorite, calcite and other silicate minerals without the use of traditional sodium silicate depressant. As sodium silicate is also a dispersant, its absence also has great advantages in water treatment and circulation. He presented this work as a poster at Flotation '17. He is also working on the removal of arsenic and other heavy metals from mining and other wastes, but this work has not yet been published.
Yanhong Wang was awarded a PhD from the University of Queensland on the mitigating effects of clays on copper flotation, which was presented by poster at Flotation '15, and she was presented with the award for best poster at the conference. She continues with this work at CSU.
Yanhong, and Kaiqi Jiang, both then with University of Queensland, with me and Jim Finch
I had lunch with Prof. Zhao Zhongwei, who is Vice Dean of the School of Metallurgy and the Environment and works closely with the Mineral Processing Vice-Dean Prof. Wei Sun on the extraction of tungsten from mainly scheelite. China is the world's largest tungsten producer, and around 80% comes from scheelite. He is also carrying out very topical work on the recovery of lithium from brines using an electrochemical method which has very high selectivity of lithium from magnesium. The work has been published in Hydrometallurgy (Volumes 133 and 176) and a pilot operation on a salt lake is now underway in Tibet.
With Profs. Zhongwei and Sun
Over morning coffee in the common room, I spoke to three more dedicated researchers. There are many lithium deposits in China and Dr. Dong Fang Lu is working on the use of mixed anionic and cationic collectors for fine spodumene flotation, as well as fine particle capture in HGMS. He is also involved with modification and optimisation of two Australian inventions, the Jameson Cell, which is being modified for spodume flotation at high altitudes, and optimisation of the Reflux Classifier to preconcentrate antimony oxide tailings.
Dr. Jian Cao has only been at CSU since July and is openly delighted about his appointment. He is an organic chemist and he is working on the design, synthesis and application of flotation reagents, particularly for serpentine depression, and new activators as an alternative to copper sulphate in pentlandite flotation. He hopes to eventually build a library of flotation reagents, to include new collectors, activators and depressants. 
Prof. Zhiguo He talked with great enthusiasm of his work on the mining of acidophiles, and their role in bioleaching and heavy metal adsorption. He has interesting results which I would like to see him present at Biomining '20 in Falmouth.
With Dong Fang Lu, Jian Cao, Zhiguo He, and Zhyong Gao
Dr. Fen Jiao introduced me to her team of fine young researchers, all of whom would be a credit to CSU if presenting work at an MEI Conference. They are researching a diverse range of topics, including the flotation of scheelite at low temperatures, selective extraction of lithium from brines, the treatment of waste waters and the biggest challenge of all, recycling metals from printed circuit boards and the recovery of lithium from spent batteries.
Fen Jiao with her team Yunfan Wang, Jiaqi Xu, Xuehu Zhong, Jianhua Kang and Ye Zhang
CSU is a major force now in mineral processing research, and in recent years has hosted many leading researchers from overseas, including Profs. Roe-Hoan Yoon, Jan Miller, Cyril O'Connor, John Ralston and Jan Cilliers. The number of publications in international conferences and journals is increasing and my second seminar "how to get your paper published in Minerals Engineering" was at first sight appropriate as 95% of all papers submitted to the journal from China are rejected, compared with a worldwide rejection rate of 82%. However, I suspect that CSU contributes little to this extremely high figure. Naturally I stressed that presenting work at an MEI conference is a great aid to publication, as the conference itself provides the first peer-review of the work, and presenting before an international audience improves confidence in presenting in English. In this respect I suggested that maybe their internal research seminars could be in English, as well as written interim reports. I believe that China's first university to teach solely in English is the Southern University of Science and Technology in Shenzhen.
I would like to thank Zhiyong and the rest of the faculty staff for making me so welcome in Changsha and conferring on me their very special honour. If you are interested in collaboration on any of the projects mentioned, please contact Dr. Zhiyong Gao at who will pass your message on to the appropriate project leader.
All in all my visit has been a real eye-opener; I have visited countless universities and research institutes over the past decades, but I can honestly say that I have never met such an impressive team of young researchers and staff. I did not have time in my short stay to discuss undergraduate teaching, but as 40% of the post-graduates are from CSU, and teaching is only by faculty members of at least Associate Professor level, then they can't be doing many things wrong! I can say with complete confidence that CSU will play a major role in the future evolution of mineral processing.
A farewell photo with some of the young mineral processing post-graduates
Twitter @barrywills

Friday, 12 October 2018

The Environmental Applications of Biotechnology in Mining

Biotechnology is set to have an increasingly important role,  not only in the treatment of primary ores and concentrates, but in the quest for the circular economy, and is likely to have a major role in remediation, treatment of tailings, electronic and other wastes, and as a potential aid to processes such as flotation. In this respect MEI's Biomining conferences are now intimately linked to the Sustainable Minerals series, which was very evident in June in Namibia, where over 60% of the Biohydromet '18 delegates also attended Sustainable Minerals '18.
Biomining '20 and Sustainable Minerals '20 will run back to back in June 2020 in the beautiful Cornish town of Falmouth (more info on the posting of 2nd August). Dr. David Dew will present a keynote at Biomining '20 on the limitations to the commercial application of biohydrometallurgy for the treatment of base metal sulfide ores (posting of 20 August), and we are pleased to announce that Dr. Anna Kaksonen, of Australia's CSIRO, will present a keynote on the environmental applications of biotechnology in mining. This will complement the keynote lecture on the following day at Sustainable Minerals '20, when Dr. Anita Parbhakar-Fox, of the University of Tasmania, will discuss how the mining industry might respond to the 'war on waste' (posting of 25th September).

Anna and her co-workers have recently published a comprehensive review article on recent progress in biohydrometallurgy and microbial characterisation (Hydrometallurgy Volume 180, September 2018). Bioprocessing of low-grade ores and concentrates is well-established as a commercial-scale technology for extracting value from various base and precious metal minerals. Microorganisms are also increasingly being used for recovering value from mine wastes, such as tailings, slags and ashes, as well as urban mining of end-of-life consumer products such as batteries and electronic wastes. The capability of microbes to catalyse oxidative and reductive bioprocesses as well as degrade organic compounds has been utilised for the removal of various contaminants from hydrometallurgical process waters and the treatment of effluents prior to release into the environment. Biological iron oxidation, bioreduction of nitrate, selenate and sulfate, neutralisation of acidity with biogenic alkalinity and bioprecipitation of metals offer alternatives for chemical water treatment. Emerging technologies, such as bioelectrochemical systems and synthetic biology are also opening new avenues to mining companies for monitoring and mitigating environmental impacts. Dr. Kaksonen will review examples of recent developments in the environmental applications of biotechnology in mining.
Anna Kaksonen has about 20 years’ experience in various aspects of biomining, from bio-oxidising and bioleaching low-grade ores to treating waste streams and recovering resources. During her Doctor of Technology degree, she developed fluidized bed reactor processes for biotechnical mine water treatment at Tampere University of Technology (TUT) in Finland. As a Senior Researcher at TUT, she also contributed to the development of heap bioleaching for complex low-grade black schist ores, bioprocesses for excess iron and sulfate removal from barren leach liquors and metal recovery from various metallurgical wastes. In 2009 Anna joined Commonwealth Scientific and Industrial Research Organisation (CSIRO), Australia as a Team Leader of Environmental and Industrial Biotechnology (EIB). In 2017 she was appointed as a leader of CSIRO’s Biotechnology and Synthetic Biology Group which has three teams (EIB; Biocatalysis and Synthetic Biology; and Metabolomics and Proteomics) located in Perth, Canberra and Brisbane. She has delivered projects to many companies on base metal, precious metal and uranium bioleaching, as well as biotechnical removal of organic and inorganic impurities from hydrometallurgical process waters. She has also been active in urban mining, developing bioprocesses for the extraction of metals from electronic wastes.
The latest updates on Biomining '20 and Sustainable Minerals '20 can be found at #Biomining20 and #SustainableMinerals20 respectively.

Tuesday, 9 October 2018

Fathi Habashi- still going strong at 90 years of age

On behalf of us all at MEI, I would like to wish the very best to Prof. Fathi Habashi, who was born in Alexandria, Egypt, 90 years ago today.
Over very many years Fathi has been a well known figure at major mineral processing conferences, presenting keynote lectures and chairing sessions. Only two years ago he delivered two presentations at the XXVIII IMPC in Quebec City, where he and his wife Nadia kindly showed me and Barbara around the campus of Laval University, at which Fathi is an Emeritus Professor. He has been quoted as saying to young people "do not stay in what is called an “ivory tower”. Travelling and attending conferences have enormous, sometimes unexpected benefits.”
At Laval University, Canada, September 2016
With Nick Hazen and the late Maurice Fuerstenau in Seattle, February 2012
Fathi is a prolific author of textbooks on extractive metallurgy and its history, and this year published the 160 page e-book Success and Failure in the Canadian Metallurgical Industry and the 170 page e-book Friends, Colleagues, and Mentors Who Passed Away. Currently he is working on the biographies of people, mainly scientists, who have influenced his long professional career either directly or indirectly.
Fathi is an inspiration to all, and I am sure he will continue to be so during his 90s.
Twitter @barrywills

Saturday, 6 October 2018

A legendary steam engine passes through Cornwall

The steam engine is surely one of the greatest of all inventions. It kick-started the Industrial Revolution, and was crucial to Cornish Mining, the powerful steam-driven pumping engines allowing deep level mining of the copper and tin ores. So it was great to see a world-famous steam engine in action in Cornwall this morning.
As a young boy in Manchester in the 1950s I was, as were most boys at that time, a keen train-spotter, but never saw the Flying Scotsman, as it serviced the London and North Eastern Railway (LNER), whereas the Lancashire region came under London Midland Scottish (LMS).
This morning I saw this iconic engine for the first time, as it passed through Truro en route to Penzance.
The Flying Scotsman passes through Truro station
The locomotive, number 60103, built in 1923 and named after the Flying Scotsman service between London and Edinburgh, set two world records for steam traction, becoming the first steam locomotive to be officially authenticated at reaching 100 miles per hour (160.9 km/h) on 30 November 1934, and then setting a record for the longest non-stop run by a steam locomotive when it ran 422 miles (679 km) on 8 August 1989 while in Australia.
Twitter @barrywills

Thursday, 4 October 2018

Cornwall's Coast to Coast Mining Trail

As well as perhaps the world's best coastal paths, Cornwall is also blessed with several interlinked inland mining heritage trails, the most well-known being the 12 mile long Coast to Coast (CC) trail (known locally as the Bissoe trail), linking what were, in the 19th century, two of the county's most important ports, Portreath on the north coast and Devoran on the south.  The Mineral Tramway Network of trails follows many of the old mining railways that connected copper and tin mines with these two busy ports, which handled imports of coal for the steam engines and the export of ore. The CC trail closely follows the horse-drawn Portreath tramroad which was opened in 1812, to service the mines in the Gwennap Parish, which were then the most important copper mines in the world. The Redruth and Chacewater Railway was built in 1825 and linked the mines around Gwennap, and those around Redruth, to the port of Devoran.
The coast to coast mining trail
For those of you spending a few days in Falmouth, before or after an MEI Conference, I have previously posted recommendations for what to do should you not have a car (posting of 11th March 2015), but if you do have a car, then there is a wealth of options in Cornwall, and if you have an interest in mining history,  then exploring the CC trail either on foot or by bicycle, is a fabulous day out.
You can park your car, have coffee or lunch, and rent a mountain bike and helmet at Elm Farm in the village of Cambrose, a couple of miles from Portreath, and from here you can either head back to the beginning of the trail at Portreath, or join the trail at Cambrose. A mountain bike, or hybrid, is advised, as the gravel and compacted earth surfaces are not really suited to road bikes, and around the intensively mined Poldice Valley the surface is hard and rocky. You will also need to keep your eyes open for the large granite route-markers, as in places the trail diverts briefly onto quiet country lanes, as well as a couple of major roads. If in doubt, wait a few minutes and you will see other cyclists who will point you in the right direction!


So, here we go, and enjoy your day!:

Portreath to Twelveheads
The trail begins by the Portreath Arms pub, directly opposite the Portreath Bakery, where you might wish to sample one of their excellent pasties. The countryside trail to Elm Farm is a pleasant two and a half miles, running parallel with the main road to Redruth.

There are a couple of other trails linking to the coast to coast, but I would certainly recommend that you take the three quarter mile short detour to Wheal Peevor (posting of 1st July 2018). You will see the waymarker after about 4 miles and the route, mainly on country lanes, takes you to three of the finest preserved engine houses in Cornwall. Unfortunately direction signs disappear as soon as you take the path from the coast to coast trail, but luckily the area is favoured with dog walkers, so there are many people to aid you on your way, of if you have GoogleMaps, then just enter Wheal Peevor.
The stamps engine house at Wheal Peevor with Portreath on the horizon
Wheal Busy
Back on the CC trail I would recommend that you avoid the Wheal Busy loop at Wheal Rose Farm, which is an unpleasant diversion with little of value to justify the effort. There is little to see at Wheal Busy, a notable copper producer from the early 1720's, apart from the rather sad ruined pumping engine house.
After 5 miles, we reach the best place for getting lost! Look carefully for the waymarkers after crossing the bridge over the busy A30. The route takes you by the Crossroads House Care Home, after which you turn right through the Fox and Hounds car-park, and then cross the road to pick up the trail again for some pleasant cycling on the tramroad through Scorrier Woods and the outskirts of Unity Woods.

Scorrier Woods
At 6 miles the Wheal Busy loop joins the trail again and it is worth taking the track through the deep and dark Unity Woods to Killifreth Mine's Hawke's Shaft pumping engine house. Killifreth was a small copper mine, and the engine house at Hawke's Shaft operated between 1893-97, and then when the mine converted to arsenic processing a bigger engine was used from 1912-21, which necessitated raising the stack to its present level, the tallest chimney in Cornwall. Be advised though that, although it is only half a mile to the engine house, the trail through the woods is definitely suited only for mountain bikes, being steep, narrow and rocky.
Unity Woods with (right) Killifreth's Hawke's Shaft pumping engine house

One of the many capped mine shafts
I suggest that you avoid the Little Beeside loop a little further on and carry on to the Poldice Valley, once the most important copper mining area in the world. Over 3,000 shafts are known to have existed in the old Gwennap parish and although today most have been capped there may still be shafts which lie in wait for the unwary amongst the gorse and bracken of the old mining district, described in the early 19th century as the richest square mile on earth.

Now is the place to travel the short distance on the Little Beeside loop to the ruins of the Poldice Mine, which was originally a tin and copper mine, and by 1685 was employing between 800 to 1000 men and boys.  By 1702 it was the deepest mine in Cornwall, having reached a depth of 106 fathoms (636 feet) and by 1788 the output of copper exceeded that of tin. Water was always a problem, and in the early 1740s five Newcomen steam engines were employed for pumping water from the mine. The mine manager John Williams planned the construction of the Poldice Deep Adit to help drain the mine, work commencing in 1748. This eventually linked up with adits from over 60 mines in the Gwennap area, to become the Great County Adit (posting of 8th August). The Gwennap mines were a fair distance from both the north and south coasts, and as a result incurred high costs to transport timber, coal and ore. In 1812 it was John Williams who constructed the horse-drawn plateway from his mines at Poldice through Scorrier to the newly-constructed harbour at Portreath. In 1867 the mine closed for the first time in its history, but resumed work again in 1870 producing arsenic, in great demand especially for the expanding Lancashire cotton industry, which used it in pigments and dyes, but by the 1910s most of the activity was over and although small-scale mining continued into the 1920s, it closed in 1930, the ruins seen now being the relics from the first arsenic works.

In the foreground below are two buddles, a convex buddle in the centre and a concave buddle to the left. These were crude, but very widely used, devices to concentrate heavy minerals such as arsenopyrite. In the background are the remains of the calciners, which were used to roast and oxidise the arsenopyrite at high temperature.
The highly poisonous arsenic trioxide was condensed as a 'white soot' in long labyrinths, which were periodically cooled and dug out by hand to recover the oxide, surely one of the worst ever jobs in mining, although they did have safety equipment including cotton wool nose plugs, handkerchiefs for breathing through and arms smeared with clay!

19th century arsenic workers
Back on the trail we are now very obviously in mining country, with the waste from centuries of mining for copper, tin, tungsten, and arsenic on both sides of our route. There are many 'off-piste' mountain bike trails meandering through the old tailings dumps, many of which have been reworked for tin and arsenic in more recent times, and the trail is now much more rugged and rocky than encountered previously.
Tailings dumps in the Poldice Valley
But after about a mile green vegetation returns, the only obvious evidence of mining activity being a few capped mine shafts and isolated tailings dumps as we approach the hamlet of Twelveheads and the Bon Appetit cafe, a great place to stop for light refreshments. From here, follow the country road and then left onto the trail a couple of hundred yards on, opposite the Wheal Andrew Counthouse. Immediately to the right on the trail is a very narrow overgrown path leading down to the Carnon River and the portal to the Great County Adit, but there is little to be gained by walking down the track, as access to the portal is now securely blocked and hidden.
A little further on look back, and above the valley are the buildings for the concentrator of the Mount Wellington tin mine, which operated between 1976 and 1991.
Twelveheads to Devoran
Nine miles from Portreath we reach the Bike Chain Bissoe Bike Hire.  Another great place to stop for light refreshments, bikes can also be rented here should you be planning a trip starting at this end of the trail.
Point Mills Arsenic Refinery
Shortly after crossing the road and rejoining the trail the last evidence of mining activity is the ruin of the Point Mills arsenic refinery, which was operated for a century, ending with the outbreak of World War 2.
The last 3 miles to Devoran Quay is an easy ride through the Bissoe and Carnon Valleys, once one of the most intensively mined regions on earth, although little evidence now remains. The highlight of this last few miles is passing under the impressive Carnon Viaduct, part of the Truro to Falmouth branch line. The  nine-arch masonry viaduct replaces an earlier structure designed by Isambard Kingdom Brunel for the Cornwall Railway and opened in 1863. The present viaduct opened in June 1933, the timberwork of the original structure being dismantled and removed, but its masonry piers still stand beside the replacement viaduct. 
The final mile of the journey is through the pretty village of Devoran, to the end of the trail at Devoran Quay on the River Fal's Restronguet Quay. The demise of Devoran as a port occurred in 1876 when disastrous floods caused the neglected County Adit to release thousands of tons of water, carrying rubbish and silt down-river to Restronguet, blocking navigation to all but the lower quays.
The end of the trail, at Devoran Quay
Twitter @barrywills
More Cornish walks
More on Cornish Mining
More on Cornwall