The mineral lepidolite is a potassium-lithium-aluminium-fluoro-phylosilicate with the chemical formula KLi2AlSi4O10F(OH). The colorless, white, yellowish or pinkish lepidolite consists of aluminum silicate, potassium and aluminum lithium hydroxide and may contain traces of rubidium. It is characterized by a good cleavage. The mineral is opaque and sensitive to acid and hot water and therefore loses its color. The average density is 2.84 and the hardness is 2.5 to 3. The crystal system is monoclinic and the stripe is white. Lepidolite is named from the Greek words lepidion and lithos, meaning "shell" and "stone" respectively. The mineral is mainly found in lithium-rich pegmatites. The type locality is Pala, San Diego, California, USA.