Orichalcum was said to be the metal used to make the Shrine of Poseidon in the very center of the Island of Atlantis, according to Plato's book, Timaeus and Critias, page 119 (link in comments). For a long time scholars have debated about the existence and possible composition of such an alloy. Now it has finally been discovered to be a mixture of Copper, Zinc and Charcoal that forms a golden brass like metal. https://www.ancient-origins.net/news-history-archaeology/more-orichalcum-atlantis-alloy-turns-helmets-sicilian-shipwreck-what-was-021254