electrum (n.)

"alloy of gold and up to 40% silver," late 14c. (in Old English elehtre), from Latin electrum "alloy of gold and silver," also "amber" (see electric). So called probably for its pale yellow color. "A word used by Greek and Latin authors in various meanings at various times" [Century Dictionary"]. In Greek, usually of amber but also of pure gold. The Romans used it of amber but also of the alloy. The sense of "amber" also occasionally is found in English. "At all times, and especially among the Latin writers, there is more or less uncertainty in regard to the meaning of this word" ["Century Dictionary"].