Orihalcon

Orichalcum
A sestertius coin from the time of Caligula
Type	Metal

Orichalcum or aurichalcum is a metal mentioned in several ancient writings, including the story of Atlantis in the Critias of Plato. Within the dialogue, Critias (460 – 403 BC) claims that orichalcum had been considered second only to gold in value and had been found and mined in many parts of Atlantis in ancient times, but that by Critias' own time orichalcum was known only by name.

Orichalcum may have been a noble metal such as platinum, as it was supposed to be mined, or one type of bronze or brass or possibly some other metal alloy. In 2015, metal ingots were found in an ancient shipwreck in Gela (Sicily), which were made of an alloy primarily consisting of copper, zinc and small percentages of nickel, lead, and iron.

In numismatics, orichalcum is the golden-colored bronze alloy used by the Roman Empire for their sestertius and dupondius coins.

The name is derived from the Greek ὀρείχαλκος, oreikhalkos (from ὄρος, oros, mountain and χαλκός, chalkos, copper), meaning literally "mountain copper".

The Romans transliterated "orichalcum" as "aurichalcum," which was thought to literally mean "gold copper". It is known from the writings of Cicero that the metal which they called orichalcum resembled gold in color but had a much lower value.

Orichalcum has been held to be a gold/copper alloy, a copper-tin or copper-zinc brass, or a metal no longer known. However, in Virgil's Aeneid, the breastplate of Turnus is described as "stiff with gold and white orichalc".