Lithium extraction from geothermal fluids
Lithium was first discovered in Cornwall in 1864 by Miller, an academic at King’s College London who was intrigued by the hot springs encountered in the Cornish mines. These hot springs occur when saline geothermal fluids circulate through fractures and faults within the granites, and discharge from the crosscourse structures and mineralised lodes due to the natural permeability of structures relative to the surrounding rock.
Miller performed the first geochemical analysis on a fluid sample taken from the Hot Lode at United Downs. The geothermal fluid was notable for its temperature of 124℉ at 230 fathoms depth (equivalent to 51℃ at 420m depth). The hot springs were often 10 degrees higher in temperature than the rock temperature at the depth they were encountered, suggesting that they had travelled from a deeper source. When these geothermal waters were tested, they were found to be ‘extremely rich in lithia’ – which was of limited commercial interest at the time. Further geochemical analyses of these hot springs at South Crofty in the 1980s confirmed the presence of consistent levels of lithium enrichment in the fluids, at concentrations which can now be economically extracted directly from the geothermal fluids by use of new technologies which have been developed in the past few years.