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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 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 and zinc, i.e. a form of brass.〔(【引用サイトリンク】title=Divers Retrieve 'Atlantis' Metal Orichalcum from Ancient Shipwreck )〕 In numismatics, orichalcum is the golden-colored bronze alloy used by the Roman Empire for their sestertius and dupondius coins.〔(【引用サイトリンク】url=http://www.forumancientcoins.com/numiswiki/view.asp?key=orichalcum )〕 == Overview == The name derives from the Greek , ''oreikhalkos'' (from , ''oros,'' mountain and , ''chalkos,'' copper or bronze), meaning literally "mountain copper" or "copper mountain". 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 they called orichalcum, while it resembled gold in colour, had a much lower value. Orichalcum has variously 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". In later years, "orichalcum" was used to describe the sulfide mineral chalcopyrite and to describe brass. However, these usages are difficult to reconcile with the claims of Plato's Critias,〔(【引用サイトリンク】title=The Internet Classics Archive - Critias by Plato )〕 who states that the metal was "only a name" by his time, while brass and chalcopyrite were very important in the time of Plato, as they still are today. Joseph Needham notes that the 18th century Bishop Richard Watson, a professor of chemistry, wrote that there was an ancient idea that there were "two sorts of brass or orichalcum". Needham also suggests that the Greeks may not have known how orichalcum was made, and that they might even have had an imitation of the original. In 2015, a number of ingots believed to be orichalcum were discovered in a sunken vessel (in the coasts of Gela in Sicily), which has tentatively been dated as being 2600 years old. Analyzed with X-ray fluorescence by Dario Panetta, of TQ - Tecnologies for Quality, the 39 ingots turned out to be an alloy consisting of 75-80 percent copper, 15-20 percent zinc, and smaller percentages of nickel, lead and iron.〔(【引用サイトリンク】title=Atlantis' Legendary Metal Found in Shipwreck )〕〔(【引用サイトリンク】title=Unusual Metal Recovered from Ancient Greek Shipwreck - Archaeology Magazine )〕 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「orichalcum」の詳細全文を読む スポンサード リンク
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