Digging deep

Materials World magazine
1 Nov 2017

The UK mining industry is showing a new focus working on a narrower range than in the past. Frances Perry attended the IOM3 conference, Current Developments in the UK Mining Industry, to discover more.

When publicity for the conference Current Developments in the UK Mining Industry gathered the Twitter response ‘UK mining industry? Is there still an industry?', the organisers were happy that the presentations would more than answer this question.

The two-day event suggested a new focus and narrower range of the mining industry than in the past. The emerging UK industry repeatedly described by speakers is one in which neither the large-scale mechanised mines of the 1970s, nor the centuries of traditional unregulated mineral working have any place. Instead, technology is directed at overcoming environmental constraints and mines are developed in response to entirely new economic markets. 

Projects are pushing ahead in not just one but three major mining regions of the UK – the Caledonian sulphide belt of Scotland and Northern Ireland hosts gold, but also barite for the North Sea oil industry. English evaporite and coal beds from the east coast to the west can supply bulk slow-release fertilisers, thermal coal for cement-making and metallurgical coal for steel. And the granite-related tin districts of Cornwall and west Devon have resumed production of tungsten, with tin in demand for electronic soldering and the hope of lithium for battery-powered cars. 

Keep it clean

It says much for this new vision that the first two project studies discussed were for extraction under national parks. Creative solutions to planning issues include a 50m deep pit to conceal a sunken headframe, a 36km tunnel to Teeside at a depth of 360m, batteries and generators to supplement a weak power supply, dry stacking of tailings to imitate glacial features and the halting of blasting on days when an ice climb by a waterfall is freezing, ready for weekend climbers. 

The two gold mines under development, Cononish and Curaghinalt, have interestingly opted for contrasting processing solutions to protect rivers in designated areas – although both have chosen dry disposal of the resulting wastes.

Scotgold Resources’ Cononish, near Tyndrum, Scotland, is to follow the gravity and flotation route to avoid the use of cyanide, whereas at Curaghinalt, Dalradian Resources has opted to take the bull by the horns and explain to the people of Northern Ireland, at a public enquiry if need be, how their proposed carbon-in-leach plant can be made safe in conjunction with cyanide destruction technology. 

At the other end of the UK, the two factors driving the reopening of South Crofty are not just price recovery (as tin replaces lead solder in the global electronics market) but also a two-month demonstration that Environment Agency standards for arsenic and manganese removal from mine water can be achieved with the addition of hydrogen peroxide, so that dewatering of the mine complex can go ahead. An even more radical approach to the hot brines that have plagued Cornish mines for centuries was presented by Cornish Lithium, which plans to extract the lithium values that have been identified from 1864 onwards – not in vast salars but by compact plants using the demonstrated new technology of reverse osmosis, ion exchange and LCE precipitation (see Materials World June 2017 for a Q&A with Jeremy Wrathall, CEO of Cornish Lithium Ltd).

Never just a hole

Although new technologies are driving many of the projects, this was not a mining technology conference – there were tantalising glimpses of the geotechnical challenges being addressed during expansion. The pit bottom at Winsford Rock Salt’s proposed Lower Bostock development has been redesigned to allow for greater salt recovery, while Cleveland Potash has had to modify its standard bord-and-pillar mining methods with an element of retreat to cater for the extreme toughness and brittleness of its polyhalite resource. The uncomplicated nature of Aberfeldy’s new, much larger barite deposit at Duntanlich, was contrasted with the convoluted Foss seam as allowing modern, mechanised mining, while in east Cornwall the Redmoor complex of sheeted veins ignored by previous miners as too narrow to extract is being drilled to identify a potentially mineable higher-grade tin-tungsten-copper resource. 

A number of projects are making good use of whatever is readily to hand – the Kilroot salt mine on Belfast Lough is using fly ash from a next-door power plant for injection grouting of its new 1.5km ventilation/access drive, and West Cumbria’s metallurgical coal resources under the Irish Sea will be accessed via two drifts from an old anhydrite mine. The focus is on smaller-scale mining of carefully identified resources by methods such as room and pillar, with equipment such as the twin-arm roof bolter, continuous miner and battery-powered scoops planned for the New Crofton coal co-operative. 

The challenges seem to be less geotechnical than environmental or even political – with comments from speakers including, ‘then along came HS2, wanting to put a rolling-stock depot on our site’ and ‘of course there isn’t a government in Stormont at the moment’. 

However, careful planning, preparation and community involvement have evidently been key to the planning permissions achieved, as has appropriate compromises such as agreeing to leave crown pillars at Nottinghamshire’s Marblaegis gypsum mine. The presentations on Marblaegis and Derbyshire’s Milldam fluorite mine exemplified mature operations quietly upgrading their reserves and optimising safety by using remote-controlled loaders at draw-points or innovative communication methods for personnel location. 

Two speakers focused on the export not of metals or bulk minerals but expertise. Andrew Watson discussed what the Mines Rescue Service can offer countries that persist in putting productivity before a safety culture, and Pat Foster pointed out the continuing value to the industry not only of the Camborne School of Mines’ graduates, but also its research output.

The conclusion was that, Twitter aside, the UK has, ‘not a sunset industry but a sunrise industry’ – and that another conference is needed in a year or two, to focus on the technical aspects of these newer mines as they develop.