21 Apr Strongbow’s South Crofty to revive age-old tin mining tradition in Cornwall
VANCOUVER (miningweekly.com) – Bolstered by strengthening tin prices and improving fundamental support in the long term, Canadian mineral exploration firm Strongbow Exploration is set to revive a mining tradition in England’s county of Cornwall, that reaches back thousands of years to the early Bronze Age.
The company’s flagship asset, the South Crofty project, is a past-producing underground tin/copper mine, located in the town of Pool, in the historic Cornwall tin mining district of south-west England. The project is located 390 km west-southwest of London, and is about 4.5 km south of the Celtic sea coast.
The Cornish mining industry, which started about 2150 BCE, reached its peak in the nineteenth century, when thousands of workers were employed in up to 2 000 mines, before the industry collapsed when ores began to be produced more cheaply abroad in Malaysia and Indonesia, among others, Strongbow president and CEO Richard Williams tells Mining Weekly Online in an interview (see attached video clip).
The resulting slump in tin prices was pushed over the edge following the collapse of the International Tin Agreement in 1985 (complex agreements between producer countries and consumer countries regulating the supply and price of tin dating back to 1921), and in the late 1970s and early 1980s, by the US government aggressively selling off its strategic tin stockpile, forcing all Cornwall’s tin mines to shutter between 1985 and 1998.
Strongbow’s flagship asset, the South Crofty mine, was the last to close in 1998.
“South Crofty survived the last 13 years of its operating life in an extremely difficult price environment, attesting to the high grades of the deposit,” Williams says.
The mine’s revival is even more urgent today, following tin prices rising about 55% in 2016 to around $22 000/t, with analysts expecting long-term prices to range between $22 000/t and $25 000/t.
Williams notes that a structural supply deficit is emerging, while new technological applications point to future expansion of the 340 000 t to 350 000 t global tin market.
South Crofty is currently on care and maintenance, and operates under permissions that were granted in 1952 and updated in 2006, with environmental conditions imposed.
Williams explains that replacement planning applications for surface and underground developments were approved by Cornwall Council in 2011 and 2013, which has increased the project area to 1 490 ha, with a working depth of 1 500 m below the surface.
The underground mining permission is valid until 2071. South Crofty’s underground permissions area includes five mineral rights, as well as areas of mineral rights that are leased or unregistered.
The project’s underground permissions extend over 26 historic mining operations, including two of the most significant mines in the Cornish tin mining district – South Crofty to the east and the Dolcoath mine to the west.
The project site is located within an industrial area with highly developed power supply and regional distribution, has two 33 kV overhead power lines that traverse the property, and a dedicated 11 kV power supply to the New Cook’s Kitchen shaft. The project also has ready access to fresh water supplied by the local South West Water utility.
Site infrastructure from prior mining and development operations includes office and warehouse buildings, and the partially refurbished New Cook’s Kitchen shaft.
Importantly, Williams says a modern decline extends to a vertical depth from surface of 120 m, with a west branch that provides access to the Upper Mine Dolcoath mineralisation, while an east branch, mined in the 1980s, was being developed to provide rubber-tyred vehicle access/secondary egress into the South Crofty mine.
Process plant facilities from previous operations have been dismantled and removed.
Strongbow acquired from administration a 100% interest in Western United Mines in July last year, giving it full ownership in the project.
Williams notes the strong historic production profile of South Crofty, with the average output in the period 1984 to 1998 totalling 191 200 t/y, at an average grade of 1.31% tin. Nearly ten-million tons were mined between 1906 and 1998, at an average grade of 1% tin. The nearby Dolcoath mine operated as an independent mine from 1895 to 1921, producing 2.14-million tons grading about 2% tin.
Strongbow has recently announced that it has completed water treatment trials at South Crofty and is now working on lodging an application to the UK Environment Agency (EA) for a mine waste permit in the coming weeks.
The company has hired global engineering and project management consultancy WS Atkins to apply to the EA for a mine waste permit with water discharge consent. The application is expected to be filed within a month and permits are likely to be issued before the end of summer this year.
“We would like to maintain the momentum we have gained over the past several months, and are in discussions with our engineering and financing teams to be able to start construction of the water treatment plant the very day after receiving the water discharge permit,” he says.
Once Strongbow receives a mine waste permit with water discharge consent, the South Crofty project will be fully permitted, including a mining licence valid to 2071; planning permission to construct new surface process facilities; and the ability to dewater the mine.
“This is an important step forward as Strongbow works to bring the South Crofty mine back into operation. The South Crofty team worked closely with the EA throughout the process and I am very pleased that we were able to develop a system to treat the mine water which met their very high standards,” Williams states.
The water treatment trials were required by the EA to demonstrate that contaminated mine water could be treated, and dissolved metals and suspended solids collected before discharging mine water from the South Crofty mine workings into the Red river. The results of the trial successfully met all treated water target contaminant levels proposed by the EA.
A February preliminary economic assessment (PEA) on the South Crofty project has calculated a net present value, at a 5% discount rate, of $130.5-million, and an internal rate of return of 23.4%, at assumed metal prices of $10/lb tin, $2.65/lb copper and $0.90/lb zinc.
South Crofty has an estimated pre-production capital cost, including contingency, of $118.7-million, with payback of 3.8 years and sustaining capital costs of $83.8-million over the eight-year life-of-mine.
The mineralised material the PEA overviews is 2.58-million tonnes containing 88-million pounds of tin equivalent, at an average grade of 1.55%.
South Crofty will be operated using modern, trackless, mechanised underground mining methods and best-in-class processing, which is based on more than 40 years of experience processing the mine’s mill feed through both the former on-site and Wheal Jane mills. The thickened tailings from the process will be used to backfill part of an eight-million-cubic-metre void space currently in the mine, as well as providing ground support for modern mining operations.
Meanwhile, Williams notes strong support to revive the project among residents and local government. “We have resounding local support in Cornwall and I look forward to updating shareholders and the local community during the summer.”
Mining in Cornwall has received unexpected support in recent years from a 2015 British Broadcast Corporation drama television series ‘Poldark’, which revolves around a British veteran of the American War of Independence returning home to discover his father has died, and left him mining rights in Cornwall. Williams notes that the series has gained popularity, resulting in rising interest in mine tours and the industry’s revival. A mine at South Crofty would have the potential to directly employ about 275 people in permanent positions.
Williams notes that there is significant exploration potential at South Crofty, below the polymetallic previously mined areas of the deposit. At depth, the tin resource increases in grade, with copper and zinc by-product diminishing. Pending the approval of drill permits, Strongbow plans to start testing priority targets later this year in parallel with its project development goals.
While it is still early days at the brownfield project, Williams is hopeful of starting production in 2020.
Strongbow is assessing the merits of launching a secondary initial public offering on the LSE’s Aim around October, potentially opening a significant additional resource of funding from generalist British-focused funds and the UK retail investor market.
Further, Strongbow has struck a definitive mineral rights agreement with Canada’s Strongbow Exploration to explore for lithium in the county. Williams says Cornish Lithium has developed a “very interesting lithium-in-brine exploration concept”.
“There are numerous historical documented occurrences of lithium-rich brines being intersected in various mines in Cornwall, and those brines are associated with specific structures. The granites and surrounding rocks are sources of lithium and have been interacting with circulating geothermal fluids for the past 250-million years.
“The objective is to define the main structures hosting the lithium enriched brines and then to determine the viability of exploiting these structures,” Williams observes.