THE TAMAR VALLEY - CRADLE OF TUNGSTEN PRODUCTION?
By Keith Loze
Keith Loze is a long-standing member of the Plymouth Mineral & Mining Club, having been a keen mineral collector and mining enthusiast for many years.
The Australian mining company Wolf Minerals announced their intention to recommence mining for tungsten and tin at Devon's disused Hemerdon Mine in 2007.
Once operations were underway, Wolf commissioned local Plymouth historian and author Chris Robinson to produce a book on mining in the area, but as Chris knew little about mining he enlisted the help of Keith.
Keith's extensive research has brought to light much new information concerning the area's mines and also the recovery and processing of wolframite, the primary ore of tungsten.
Sadly, Wolf's operations came to an untimely end in October 2018 and the book's future looked in doubt, but fortunately a new sponsor has now been found and Keith's research continues, with publication expected in August 2019.
The following article appeared in the February 2019 edition of the Plymouth Mineral & Mining Club Journal.
Whilst researching the Hemerdon story I became aware of the importance of the Tamar Valley in the development of wolfram processing, and the part played by the local family of Terrells, mining engineers. This article tries to link the Tamar Valley developments to the Hemerdon story, and I hope you find it as interesting as I found the research!
In both Devon & Cornwall, wolfram, the ore from which tungsten is produced (i.e. wolframite), generally occurs in association with tin ores. However for many years tungsten had little or no commercial value, particularly during the westcountry mining-boom of the earlier 1800’s, and wolframite was seen as a source of contamination. In fact, when tin was concentrated it would lose value per ton if it was found to contain even low proportions of wolfram. It was very difficult to process using traditional methods as both tin and tungsten ores have similar high specific gravity (average 7.0 and 7.3 respectively), therefore if wolframite was found during tin processing the Old Men would typically discard it along with other gangue materials.
However a use for tungsten was inevitably discovered, as a result of which the Gunnislake area of the Tamar Valley could arguably be termed “the cradle of tungsten production” when not just one, but two, processes were developed at local mines. The first was the ‘Oxland process’ installed at Drakewalls Mine, and this was followed later by a process installed at Gunnislake Clitters Mine, just a few miles away, where the local Terrell family of mining engineers were to work with new technology prior to WW1. As a result of this, and the ensuing conflict, eventually one of the Terrell brothers was to become responsible for the wolfram project at Hemerdon.
Wolframite embedded in quartz collected from Hemerdon Quarry in Oktober 2007.
Collection: Richard De Nul - Image width: ca. 40 mm.
Drakewalls was the first mine in the UK to use the Oxland Process to separate wolfram away from the tin. What is even more interesting is that the inventor was Dr Robert Oxland, a local chemist and metallurgist who lived at 8 Portland Square, Plymouth, which at that time comprised rather grand houses, but which are sadly no more and the area is subsumed into the university campus. Oxland had patented his manufacturing process, for extracting ‘sodium tungstate’ (‘tungstate of soda’), tungstic acid, and the metal tungsten itself, in 1847. A decade later, this time with inestimable consequences, he followed up with a further new process, for producing the very hard alloy of tungsten steel, in 1857.
The first mention of tungsten in the official mineral statistics was in 1858, by which time the process had also been introduced at Kit Hill, and in the same year tungstate of soda was sold by both Drakewalls and Kit Hill Mines. The process is described as follows by Collings Mining Journal of 1915:
“The process included the ‘burnt whits’ (*1) being buddled or tabled to get rid of silica or other light waste, mixed with soda-ash in the proportion of about 50% of wolfram present, heated to a considerable temperature in a reverberatory furnace for several hours, being stirred during the process, thus converting the wolfram into tungstate of soda. The mass is then thrown into lixiviating vats (*2), the solution is drawn off into evaporating pans where the tungstate is crystallised out. The tin present can be separated after pulverisation.”
Dr Oxland is also recorded thus in the illustrated catalogue of the ‘Industry of all Nations’ in 1851: “The Great Exhibition. He exhibited a case containing illustrations of tin ore containing wolfram, and with it being removed”. Frank Booker, in “Industrial Archaeology of the Tamar Valley” [David & Charles, Newton Abbot (1967)] recorded that the machinery at Drakewalls was erected at Dr Oxland’s own expense, and that he also provided the ‘soda’ for the process free of charge.
More Patents were to follow, with John Hocking of Redruth helping, registered in 1875, this time for improvements in calcining of ores. Furthermore, in ‘Pepper’s Playbook of Metals’, in 1866 he talks of Oxland, stating
“It has lately been applied with success by Mr Oxland of Plymouth in the manufacture of the hardest steel which is said that it will bore through and file ordinary steel”!
He also noted that ‘Oxland should be consulted on armour for ships’, which underlines this historic landmark moment for the birth of tungsten-steel. However, he also hinted
“…since Oxland has discovered a mode for separating the tin and wolfram it is now likely that the price of wolfram should take a respectable position in the metal market”
The Germans, however, were always ahead of the game in mining technology and processing, and around 1900 wolfram/tungsten processing was to be even more improved by the use of ‘magnetic separation’. About that time they also had their own wolfram mine, the only one outside Devon & Cornwall to produce the mineral, which was, paradoxically, not in Germany but the Carrock Mine in Cumbria! This was a ‘sole-producer’ (i.e. only wolfram) as with Castle-an-Dinas Mine in Cornwall (the prominent hillside engine house overlooking the A30 as it crosses Goss Moor) and Hemerdon outside Plymouth. The Cumbria wolfram mine was first worked in 1854, was known as ‘Carrock Mines Ltd’ in 1902, and fell idle in 1905. It was then reopened in 1906 by two Germans, William Boss and Frederick Boehm, trading as Cumbrian Mining Co Ltd; unfortunately both gentlemen were subsequently removed when British relations with Germany deteriorated. By 1911 production had again ceased, only to re-commence as The Carrock Mining Syndicate under a group of steel manufacturers until operations again stopped in 1917.
Heading southwest again however, to the Tamar Valley, the local area was once again to take the lead when a Witherill (German) type separator was to be installed at Gunnislake Clitters, replacing the earlier Oxland process. The Jan 2, 1904 edition of “Mining World” reported on the first AGM of Gunnislake Clitters relating to the new process:
“We commenced negotiations with the view of purchasing a Wetherill electromagnetic separator. At the time we commenced negotiations the price asked was prohibitive, but a new separator was brought out which was of a much more satisfactory character and after inspection by our consulting engineer and our director Mr A Schiff we were able to obtain a separator which left us a satisfactory profit in treating our mixed concentrates.”
“Initial difficulties have been overcome solving the treatment of these complex ores. We have been pioneers in the matter, we have now a plant which is practically second to none in the world and is the finest of its sort in Cornwall.”
The following year, October 19, 1905, a paper was presented to the Institution of Mining and Metallurgy at the Geological Society reporting on the treatment of tin, wolfram, and copper ores at Clitters:
“The magnetic separator used at Clitters is the Wetherill magnetic machine known by the makers as the crossbelt type”. “A wooden frame carrying two pairs of electro-magnets, two magnets are beneath the main conveying belt and two above arranged so that the N Pole of one magnet is opposite the S Pole of the other.”
It was at Gunnislake Clitters that Ernest Terrell (1879-1923) was to work with his two younger brothers, Fred (1884) and Stephen (1885). The Terrell family had originally moved up from Redruth after which grandparents Stephen and Emily had nine children, all born in Calstock between 1849 and 1868. This was not, however, the first time that the family name had been recorded in the Tamar Valley, the first mention being for a Samuel Terrell in 1794 when he was captain of Drakewalls when it was then being let!
However, fast-forwarding, our Ernest Terrell was born in 1879 in Gunnislake, by 1901 was married and listed as a ‘mine surveyor’ and a ‘mining service analyst’ (*3), and by 1903 had become a Freemason. By 1906 Ernest was still at Clitters and earned a mention in the Mining Journal, reporting on ‘the 3rd ordinary General Meeting’:
“….The services of staff – there is one thing I must mention and that is that we are indebted to our manager Mr Josiah Paul and assistants Messrs Merton and Terrell and the rest of the staff for their good work during the past year.”
He attributed much of his experience gained at Gunnislake Clitters to Josiah Paul whom he regarded as his ‘guide and mentor in all things mining’.
At the age of twenty-eight (1907) Ernest was appointed manager of Stormsdown Mine (some tin, mainly arsenic) near Ashburton in Devon, where extensive use of electric power was in use as well as magnetic separators. In the same year he was also to be responsible for bringing Devon Wheal Friendship into production at Mary Tavy. Both Stormsdown Mine and DWF were owned by a Mr Herbert Bayldon.
In 1916 Ernest appears again, this time with British Tungsten Mines Ltd where he designed and supervised the construction of a large alluvial operation at Buttern Hill Mine on Bodmin Moor (on remote moorland between Davidstow airfield and Altarnun).
It was also during this fraught First World War period that Ernest Terrell was to design and run the new wolfram mill at Hemerdon, another step up the ladder. That, however, is part of the full Hemerdon Story which is to be published during the summer of 2019.
*1 Can anyone help with this expression?
*2: Wiki: to separate into soluble and insoluble components through percolation; to leach.
*3 Consultant ?
• Correspondence with Doug Westaway
• Records from Calstock archive
• Mining Magazine 1915
• “A Tamar Valley Engineer” - Helen Wilson (FOTV - Friends of the Tamar Valley)
• DTRG - Dartmoor Tin Research Group - Newsletter, May 2016
• Correspondence with Tony Brooks
• Personal Records
• British Newspaper Archives website
• Pepper’s Playbook of Minerals 1866