Modern Olympic gold medals are made primarily from silver, with a relatively small amount of gold on the surface.
Under the International Olympic Committee’s stated material rule, a first-place medal is at least 92.5% silver and is plated with 6 grams of gold. The silver core supplies most of the medal’s mass, while the gold coating provides the traditional color and symbolism. Host organizing committees design the medals, subject to IOC approval, so exact appearance and construction can vary between Games.
The “gold medal” name therefore refers to rank, not to solid-gold composition. Historically, there was a period when gold medals really were solid gold: the medals from the 1904, 1908 and 1912 Olympics were made of solid gold. The practice changed because producing large solid-gold medals was costly and impractical.
The silver core also explains why Olympic gold medals are often described as silver-gilt. The first Olympic medals, awarded at Athens 1896, used a different gold-and-silver arrangement, and the IOC later assigned the modern gold, silver and bronze labels retroactively to the top three competitors.