Orichalcum

What it is

Orichalcum is a metal that appears in a number of texts from the ancient world. Its best-known setting is Plato's dialogue Critias, in the Atlantis story, where the metal ranked just below gold and was mined across the island in early times, though by the day of the speaker, Critias, only the name survived. The word also describes materials that can be studied: pure copper, bronze alloys and, above all, brass, including the metal of Roman coinage. It sits between metallurgy and legend, a named substance whose identity is still argued over.

Where it comes from

The English word comes from Greek oreikhalkos, built from oros, mountain, and chalkos, copper, so literally mountain copper. Roman writers transliterated it as orichalcum, and sometimes as aurichalcum, reading the opening as aurum, gold, which produced the sense gold copper. The oldest mentions are attributed to Hesiod in the seventh century BC and to the Homeric hymn to Aphrodite, dated to the 630s BC. Plato's Critias gives the Atlantis story and states that the metal was by then only a name.

Tools and materials

What the metal was made of is described in several ways. Nero's sestertii, called orichalcum, were brass of four parts copper to one part zinc. Pseudo-Aristotle writes of a copper that is very shiny and white, not through tin but because an earth has been melted with it; that earth, cadmia, came from the shores of the Black Sea and is identified as zinc oxide. Pliny held that orichalcum was a natural ore rather than an alloy. The recovered ingots are mostly copper with zinc, plus lead, nickel and iron.

What it is for

In Plato's account the metal is a mark of wealth and honour. It ranked next to gold, and the citadel of Atlantis with its Temple of Poseidon was finished in it: walls, pillars and floors were covered with orichalcum, and the roof mixed gold, silver and orichalcum. A pillar of the metal at the temple's centre carried the laws of Poseidon and the records of his first sons. In Roman use the same name went to the brass of coins, and numismatists rank it above copper.

Peoples and places

Greek writers used the word in different senses. Some meant a gold and copper alloy like rose gold, others pure copper, copper ore or copper compounds; copper-tin and copper-zinc alloys were also proposed, and some thought the original metal was no longer known. Roman authors took the term over and applied it to brass: Cicero says the metal resembled gold in colour but was worth less, Virgil gives Turnus a breastplate stiff with gold and white orichalc, and Plautus makes jokes about it whose meaning is unclear. Pliny wrote that the mines had run out.

What people believe

The best-known home of orichalcum is the island of Atlantis in Plato's Critias. There it belongs to the sacred architecture of Poseidon's temple: the outer wall of the citadel is said to flash with its red light, and the inner walls, columns and floor are described as covered with it. At the centre stood a pillar of orichalcum inscribed with the god's laws and with records of the first princes, his sons. The metal is thus part of a story about a god's laws, a royal line and wealth that was later lost.

How scholars and sceptics see it

Researchers treat the word as a puzzle of identification. Analyses of the Sicilian ingots used X-ray fluorescence and later ICP-OES and ICP-MS, and the results are read as high-quality brass. Pliny the Elder wrote that orichalcum had gone out of use because the mines were exhausted. The chemist Joseph Needham notes that Bishop Richard Watson, an eighteenth-century professor of chemistry, recorded an old idea of two sorts of brass or orichalcum, and suggests the Greeks may not have known how it was made, or may have used an imitation.

Compare and confuse

The name overlaps with several materials. It is used for brass, for the sulfide mineral chalcopyrite, and in older speculation for platinum, since the metal in Plato was said to be mined. Roman orichalcum is the term numismatists reserve for the brass of as, sestertius, dupondius and semis coins. Aurichalcum and orichalc are spelling variants of the same word.

Today

In 2015 a sunken vessel off Gela in Sicily yielded 39 metal ingots, tentatively dated to about 2,600 years ago, and another 47 were recovered in February 2016; researchers call the metal orichalcum on the basis of its composition. Outside metallurgy the name lives in games: it is an Atlantean resource in the city builder Poseidon: Master of Atlantis, and Dungeons & Dragons calls it an ultimate metal that alchemical metallurgists seek, yellow, light as air, and too hard to bend or scratch.

Questions people ask about Orichalcum

Good reading and sources

• Orichalcum on WikipediaEncyclopedia
• More photos on Wikimedia CommonsPhotos and video
• Wikidata recordOpen data