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The lightest of any solid element, lithium has, until now, played a modest role in industry. Silvery in color, and softer than lead, it has been used mainly as an alloy of aluminum, a base for automobile grease, and in the production of glass and ceramics. It is so unstable that it is never found in its pure form in nature. Lithium floats on water—or, rather, it skitters wildly about, trailing a vapor cloud of hydrogen, until it dissolves.