Mercury possesses an abundance of rare and heavy metals that are rare on Earth and unknown in other parts of the Solar System, including: copper; Yttrium, used for armaments (The Demons of Darkside); pitchblende, from which Radium and Uranium can be extracted (A World is Born); and the rare radioactive crystal known as the sun-stone (Shannach – the Last).
Originally owned by the gold prospector Gilbert Labine, Eldorado began to prospect for pitchblende ore in 1929 and set up the Port Radium mine in the Northwest Territories four years later.