Electrum, Gold and Silver Combined

Electrum occurs both naturally, panned as pale gold from riverbeds, and artificially, alloyed on purpose once smiths learned to control the ratio. The natural form found in the Pactolus river in Lydia supplied the metal for what are generally considered the world's first true coins, struck in Lydia and the neighboring Ionian Greek cities in the seventh century BCE. Because the gold-to-silver ratio in natural electrum was not consistent from one nugget to the next, those early coins were valued by weight and stamp rather than by a fixed metal content, an uncertainty that later Lydian and Persian rulers moved to solve by minting separate pure gold and pure silver coinage instead.

Pliny the Elder and other ancient writers called it "white gold" for its pale color, distinct from the yellow of unalloyed gold, and treated it as its own recognized metal rather than as merely impure gold. Modern jewelers still use the word for gold-silver alloys made on purpose, though the deliberately proportioned kind has little to do with the variable natural metal the ancient world worked with.