Quiz: Remember the definition of mal de mer?
the most common lithium mineral, basic potassium and lithium aluminosilicate; a member of the common mica group. It is economically important as a major source of lithium. Because it is one of the few minerals containing appreciable amounts of rubidium, it is useful in determining geological age according to strontium-rubidium ratios. Lepidolite occurs almost exclusively in granite pegmatites. For chemical formula and detailed physical properties, see mica (table)