Cornish Lithium finds “globally significant” lithium grades in geothermal waters and prepares for work on pilot plant

The Cornish mining district is a world-class mineral province, with estimated historic production of around £45 billion from tin and £11 billion from copper at current prices. The well-known granite outcrops (from Dartmoor in the east to the Isles of Scilly in the west) are connected deep below the surface and form one of the top five lithium-enriched granite areas worldwide, according to the United States Geological Survey. As geothermal fluids circulate in the earth’s crust, lithium is leached out of the granite into solution. Lithium in brine was first identified in ‘hot springs’ in 1864 when such fluids were discovered underground in one of Cornwall’s historic tin mines and analysed for its lithium content.

There was great news yesterday from Cornish Lithium Ltd, an innovative mineral exploration company exploring for lithium and other battery metals in the South West of the UK. Results of preliminary sampling of lithium in deep geothermal waters at the United Downs Deep Geothermal Power Project near Redruth (MEI Blog 1st November 2018) indicate some of the world’s highest grades of lithium and best overall chemical qualities encountered in published records for geothermal waters anywhere in the world. Geothermal waters which contain lithium are very different from other occurrences of lithium in brine given that the same water can be used to generate zero-carbon electrical power and heat. As such these waters are rapidly becoming recognised as the ultimate ethical source of lithium.

Jeremy Wrathall, CEO & Founder of Cornish Lithium and a graduate of Camborne School of Mines, said: “This is an exciting step towards the realisation of low-carbon lithium extraction from geothermal waters in Cornwall, and complements Cornish Lithium’s work to date on exploring for lithium contained within shallower geothermal waters in the County. The pilot lithium extraction plant, part funded by the UK Government, that we will develop with Geothermal Engineering Ltd. at the United Downs Deep Geothermal Power Project will allow us to evaluate green Direct Lithium Extraction (DLE) technologies which will bring us another step closer to commercial production of lithium in Cornwall. We now have increased confidence that these lithium-enriched geothermal waters can be found at depth across Cornwall and believe that there is significant potential to replicate combined lithium and geothermal extraction plants in different locations across the County where Cornish Lithium has mineral rights agreements in place.”

The initial assay results show lithium concentrations of up to 260 mg/L, which are believed to be among the highest published grades of lithium in geothermal waters globally. Importantly the Total Dissolved Solids (‘TDS’) content of these Cornish waters is exceptionally low relative to other geothermal waters worldwide, making Cornish waters globally significant. In particular magnesium, a metal that makes processing more difficult and expensive, is extremely low at a concentration of only 5mg/L.

The graph below illustrates the results in a global context and shows lithium levels relative to TDS for various types of lithium rich waters and brines, such as salar brines from the Atacama Desert, oilfield brines and other geothermal waters. Whilst salar brines are often much higher grade, they are difficult to process due to the presence of high levels of magnesium and other deleterious elements. Access to power in these remote locations also makes DLE challenging, or impossible.

These results are considered highly encouraging given current developments in lithium extraction using DLE technologies. Additional testing is planned over coming weeks. DLE technology extracts dissolved lithium compounds from the water without the need for the large evaporation ponds that are used in the arid regions of South America. It uses ionic adsorbents and/or ion exchange membranes, with the residual water being returned to depth via a borehole.

Using DLE technology Cornish Lithium aims to maximise product recovery from the geothermal waters in a small footprint, energy efficient extraction plant, which will be powered by an on-site geothermal power plant. This demonstration lithium extraction pilot plant will trial environmentally-responsible DLE technology to selectively remove lithium compounds from water extracted by the geothermal powerplant from its 5.2km deep borehole. Once the lithium has been extracted, the water will be reinjected into the rock.

An elegant process

The pilot plant at the United Downs Deep Geothermal Power Project will allow detailed evaluation of potential processing methodologies and accelerate efforts towards commercial production of lithium for automotive manufacturers seeking low carbon supply chains of battery metals. Domestic production of this critical metal is vital for the UK to deliver its zero carbon and clean growth ambitions.

Next steps include further sampling of the deep geothermal waters when GEL commences its next phase of test work at the United Downs site in October this year, with further tests expected to provide additional observations regarding the origins and context of these deeper geothermal waters. The information from additional bulk samples will then be used to inform the design and technology for the pilot DLE plant for the production of lithium hydroxide with a net zero carbon footprint.

The co-production of lithium with geothermal heat and power from the same geothermal waters is a truly exciting opportunity for Cornwall.

@barrywills