Gold
Gold
A soft metallic element found in small amounts on Earth and distributed in quantities throughout the universe. Gold's rarity, attractiveness, resistence to tarnish, and workability have made it valuable to humans for thousands of years.
Superman and Superboy deal with gold throughout their careers, as it desirable to criminals and villains and because of its presence at Fort Knox. Once, Superboy even retreats underground to replace the gold of Fort Knox (SB No. 59/1, Sep 1957: "Superboy's Underground Exile").
Superbaby once travels to the earth's past in search of gold when he overhears that Martha Kent "needs" it (she has misplaced an earring), stopping at Sutter's Mill, the time of King Solomon, and ancient Greece when the Golden Fleece existed (SB No. 120/3, Apr 1965: "Superbaby's Golden Quest!").
Gold is very common on Krypton and has no economic value. It is so plentiful it seeps in quantity from the Gold Volcano -- however, the beauty of gold is still acknowledged by Kryptonians as they visit the volcano as a popular tourist destination (for example, see S No. 141, Nov 1960: "Superman's Return to Krypton!").
