Lithium Lithium Lithium (from ) is a chemical element with symbol Li and atomic number 3. It is a soft, silvery-white alkali metal. Under standard conditions, it is the lightest metal and the lightest solid element. Like all alkali metals, lithium is highly reactive and flammable, and is stored in mineral oil. When cut, it exhibits a metallic luster, but moist air corrodes it quickly to a dull silvery gray, then black tarnish. It never occurs freely in nature, but only in (usually ionic) compounds, such as pegmatitic minerals which were once the main source of lithium. Due to its solubility
Rare-earth element are primarily a function of the chemistry of the source where the rock came from, as well as the fractionation history the rock has undergone. Fractionation is in turn a function of the partition coefficients of each element. Partition coefficients are responsible for the fractionation of a trace elements (including rare-earth elements) into the liquid phase (the melt/magma) into the solid phase (the mineral). If an element preferentially remains in the solid phase it is termed ‘compatible’, and it preferentially partitions into the melt phase it is described as ‘incompatible’. Each element has a different partition coefficient, and therefore fractionates