By Björn Björklund

“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) says 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’s own time, orichalcum was known only by name”.

“The name is derived from the Greek ὀρείχαλκος, oreikhalkos (from ὄρος, oros, mountain and χαλκός, chalkos, copper), literally meaning ‘mountain copper’ (Wikipedia on Orichalcum).

Χαλκός can also mean “bronze”.

“χαλκός

“copper, Lat. aes, Hom., etc.; called in reference to its colour, ἐρυθρός, Il.:—copper was the first metal wrought for use, τοῖς δ᾽ ἦν χάλκεα μὲν τεύχη χάλκεοι δέ τε οἶκοι, χαλκῷ δ᾽ ἐργάζοντο, μέλας δ᾽ οὐκ ἔσκε σίδηρος Hes.:—hence χαλκός came to be used for metal in general; and, when men learnt to work iron, χαλκός was used for σίδηρος, and χαλκεύς came to mean a blacksmith. χαλκός also meant bronze (i. e. copper alloyed with tin), not brass (i. e. copper alloyed with zinc, which was a later invention), and this was its sense when applied to arms (The Greek-Engish Lexicon of Liddell and Scott).

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“Pure boron appears as a yellowish-brown crystal” (The World Book Encyclopedia). Bronze is “a brown alloy of copper and tin” and “bronze” also means “a yellowish brown or reddish brown [colour]” (The World Book Dictionary).

“Because it is so light and has a high combustion heat, boron is important in high-energy fuels” (The World Book Encyclopedia). A “starter fuel” containing boron has been used to light the rocket fuel in some SpaceX rockets.

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“In Virgil’s Aeneid, the breastplate of Turnus is described as ‘stiff with gold and white orichalc’.

“Pliny the Elder points out that orichalcum had lost currency due to the mines being exhausted. Pseudo-Aristotle in De mirabilibus auscultationibus describes a type of copper that is ‘very shiny and white, not because there is tin mixed with it, but because some earth is combined and molten with it’” (Wikipedia on Orichalcum).

The “white” orichalcum can be identified as boric acid and also as borax. Both of these compounds are white and are naturally occurring minerals from which boron is extracted.

“Boric acid, more specifically orthoboric acid, is a compound of boron, oxygen, and hydrogen with formula B(OH)3. It may also be called hydrogen orthoborate, trihydroxidoboron or boracic acid. It is usually encountered as colorless crystals or a white powder, that dissolves in water, and occurs in nature as the mineral sassolite”.

Chemical formula BH3O3

Molar mass 61.83 g·mol−1

Appearance White crystalline solid

Density 1.435 grams per cubic centimetre.

(Wikipedia on Boric acid).

“Sassolite is a borate mineral, specifically the mineral form of boric acid. It is usually white to gray, and colourless in transmitted light” (Wikipedia on Sassolite).

“πολιός

“gray, grizzled, grisly, of wolves, of iron, of the sea, Il.” (Middle Liddell).

An ancient Greek author described the colour of orichalcum as Greek πολιός.

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The word orei “mountain” in oreikhalkos is a minor puzzle which does not affect the argument presented above. It arises because there is no difference between an element found on a mountain and the same element found on a low plain. Perhaps orei is a mistake for a word meaning “not heavy”) and therefore the correct name meant “light copper”.

A knowledgeable ancient person examining a specimen of pure solid boron would certainly have noticed two remarkable things about it: its yellowish-brown colour was like that of copper or bronze, and it was very light in weight compared with copper or bronze. Thus it seems plausible that the Greek orei “mountain” in oreikhalkos is a mistake for some presently unknown non-Greek word meaning “light, not heavy”.

The density of water is 1.0 gram per millilitre or cubic centimetre.

The density of boron is 2.08 grams per cubic centimetre.

The density of copper is 8.935 grams per cubic centimetre. So boron is very much lighter than copper and only twice as heavy as water.

Perhaps the mistake was made in translating the non-Greek language of the exotic land where orichalcum was found; this language might have possessed an ambiguous word meaning “light (not heavy)” and alternatively ”mountain”.

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This article itself contains an ambiguous English word: “light”, which can mean “not heavy” and “visible electromagnetic radiation”. So it was necessary to indicate the sense in which it was used here.

©Björn Björklund 2025