A Roman rock-crystal icosahedron (20-sided dice) in the Louvre

Here’s a pretty image that floats around the web:

It’s ancient, and an icosahedron – a 20-sided dice.[1] The Musée du Louvre twitter account (@MuseeLouvre) posted further images of what is plainly the same item (click to enlarge).

The inventory number seems to be MNC882.[2]  It is a pity that the Louvre is not as advanced as the British Museum in placing its collections online.

The Louvre account tells us that it is 1cm high, rock crystal – “en cristal de roche” – and Roman empire period.

Each face has a Latin letter on it, and also the corresponding Roman numeral.  The ten lateral faces bear the letters A to K, and the numerals 1 to 10.  The upper five triangles bear the letters L to P and the numbers 11 to 15.  The lower five triangles bear the letters Q to V, and the numbers 16-20.[3]

The inscriptions on the Louvre rock-crystal icosahedron.

This item is by no means unique.  A considerable number of polyhedral dice have been recovered from all over the Roman empire.  The majority are inscribed with Greek or Latin numbers or letters.

One unique example was an icosahedron – 20 sided dice – found in Egypt, which had the name of a different Egyptian god on each side.[4]

What were these things used for?  Obviously they were intended to be thrown, and to give a random result.  But what then?

One often-heard explanation is that they were used in conjunction with divination handbooks.  There is a 2nd/3rd century Greek oracle book, the Homeromanteion, preserved in three papyri, which refers to throwing lots to obtain a number, which can be used to look up ready-prepared oracle questions and answers.[5]  It is amusing to discover a website that allows the reader to throw the three dice and looks up the answer!  It’s at http://www.homeromanteion.com/.

 Likewise an inscription at Olympus gives another such a set of prophecies, one per letter/number of the Greek alphabet.  (There is an online version of it here.)  The Metropolitan Museum in New York has an icosahedron from Egypt, either Ptolemaic or Roman, with Greek numbers (online here).

But of course we cannot know for sure precisely what our dice was used for.

For those who wish to know more about ancient dice, there is a wonderful bibliography in this forum thread “Random Facets from the History of Dice” at boardgamegeek.com (!)

  1. [1]Strictly we should say “die”, plural “dice” in English, but I have never ever heard anybody refer to a single die as anything but “throw the dice”.
  2. [2]Listed at a website called Réunion des Musées Nationaux here, giving the date only as “Roman Empire”.  This seems to be the source of our original photograph.
  3. [3]This description and illustration from Minas-Nerpel; another transcription appears in F. N. David, Games, Gods, and Gambling: A History of Probability and Statistical Ideas, (1998) p.12.  Google Books Preview.
  4. [4]Martina Minas-Nerpel, “A demotic inscribed icosahedron from Dakleh oasis”, Journal of Egyptian Archaeology 93 (2007), 137-148.  Online at https://core.ac.uk/download/pdf/160449173.pdf.
  5. [5]More information here.