Ukraine has offered to strike a deal with U.S. President Donald Trump for continued American military aid in exchange for developing Ukraine’s mineral industry, which could provide a valuable source of the rare earth elements that are essential for many kinds of technology.

With obscure names like lutetium and dysprosium, rare earths are used in everything from iPhones and magnetic resonance imaging machines to missile guidance systems. More recently, demand has been propelled by the green tech that is helping to cut carbon emissions.