Known hard rock lithium occurrences in Cornwall occur within “Zinnwaldite” mica in granites.
Zinnwaldite has a complex crystal structure KLiFe2+Al2Si3O10F1.5(OH)0.5 and a maximum theoretical grade of 3.42% Li2O in the pure mineral. There is currently no lithium production in the world from lithium micas which explains the need for a new process and Imerys British Lithium’s focus on metallurgical research and development.
Hard rock lithium spodumene deposits in Australia are the world’s largest source of lithium. Spodumene occurs as large crystals of relatively high lithium grade material LiAl(Si2O6) with a less complex structure than lithium mica and theoretical Li2O grade of 8.035% in the pure mineral, which is significantly higher than in micas. Seven mines in Western Australia use floatation to produce a spodumene concentrate of +6% Li which is shipped to refineries in China. Recovery rates of lithium to concentrate using floatation are however low, typically only 60% to 70%. The high grade of spodumene concentrate and availability of the Chinese market has however enabled Australian miners to rapidly develop and expand their lithium production.
To compete with spodumene, production of lithium from micas requires a unique and highly efficient physical beneficiation process to produce a concentrate with high recovery followed by environmentally friendly alkaline leach and purification. There are currently no refiners globally who can process Zinnwaldite concentrate and so a complete plant from mine, to beneficiation, to refining will be needed in Cornwall.
Imerys British Lithium’s engineers have successfully beneficiated Cornish micas using our unique process to produce a +4% Li Lithium concentrate with recovery over 90%. Note that the grade achieved was higher than the theoretical maximum possible. We have also conducted numerous low-temperature calcining trials, leach and purification producing battery grade lithium carbonate. Successful metallurgical research and process development is critical to demonstrating the potential for economic recovery of Lithium in Cornwall and much remains to be done.