Lithium

Lithium is the lightest of all metals: it floats on water, then reacts with it, fizzing as it releases hydrogen. Because it reacts so readily, it is never found pure in nature. It is mined from hard-rock minerals such as spodumene, mostly in Australia, and pumped as salty brine from beneath dry salt flats in Chile and Argentina, where the water is left to evaporate in the sun.

Its biggest use by far is in rechargeable lithium-ion batteries, which power phones, laptops and electric cars. Lithium also goes into heat-resistant glass and ceramics, long-lasting greases, and medicines that treat bipolar disorder.