Portugal is rich in its lithium subsoil, which is especially concentrated in the districts of Guarda, Viseu, Vila Real and Viana do Castelo, while most of the country's lithium comes from the Gonçalo aplite-pegmatite field. The largest lithium mine in Europe is operated by Grupo Mota, Felmica, in the Guarda region, which is estimated to have reserves for 30 years of production. It has 5 more deposits in its possession. Savannah Resources in May 2018 announced a 52% increase in the estimated lithium resources at the Mina do Barroso Lithium Project in northern Portugal, saying the country could become the first European supplier of spodumene, a lithium-bearing mineral. The company said the estimated mineral resources at the mine now stood at 14 million tonnes. Lithium prices have risen in expectation of growing demand for the mineral, which is used in batteries for electric vehicles and for storing electricity from the power grid. Europe consumes more than 20 per cent of the global supply of battery-grade lithium but currently has to import all its supplies of the mineral.