The largest concentrations of lithiumcontaining minerals are found in granitic pegmatites. The most important of these minerals are spodumene (Li 2 O, Al 2 O 3. 4SiO 2) and petalite (Li 2 O, Al 2 O 3. 8SiO 2). Spodumene has a theoretical Li2O content of %. Due to its high lithium content, spodumene is considered the most important lithium ore mineral.