Lepidolite is a lilac-gray or rose-colored member of the mica group of minerals with chemical formula K(Li,Al)3(Al,Si,Rb)4O10(F,OH)2. It is the most abundant lithium-bearing mineral and is a secondary source of this metal. It is the major source of the alkali metal rubidium.
Lepidolite is found with other lithium-bearing minerals, such as spodumene, in pegmatite bodies. It has also been found in high-temperature quartz veins, greisens and granite.