All That Glitters, Experiment 6 and final

So, as just described, almost my first academic action of 2016 – for that is how far in the past we are for this post – was to head back to Birmingham, freshly remobilised, to pursue what was supposed to be the last run of experiments in the All That Glitters project of which I have now told you so much. Since the last one of those posts was only a short while ago, I’ll not reprise the project plan beyond saying it was to try and find out what was in Byzantine gold coins besides gold using X-ray fluorescence spectrometry and we were finding it difficult to get beyond what was on Byzantine gold coins. Now, read on!

Gold solidus of Emperor Constantine VI and Empress Eirini, Barber Institute of Fine Arts B4599

Gold solidus of Emperor Constantine VI and Empress Eirini, Barber Institute of Fine Arts B4599, in XRF analysis sample cup

Since we now more or less had a working method established, if it could be called that (since it didn’t really work), we had decided that our original research goal, of spotting changes in the trace elements in the centrally-minted gold coinage of the Byzantine Empire, was beyond the technology, and we needed to work out what else we could do with the remaining machine time. At first we’d thought we wouldn’t have enough, now we had more than we knew what to do with… But the most obvious thing seemed to be to broaden our sample as much as possible. So, we selected more of the Barber Institute’s coins, taken from imperial reigns we hadn’t covered, extra denominations from ones we had and sets from other mints than Constantinople that we could compare to coins of the same emperors there, and we took them all over to University of Birmingham’s School of Chemistry over a period of four days, where we were as usual excellently looked after as far as they could manage, and we subjected them to analysis. In all of this we were hampered by the fact that results were basically hard to reproduce; in fact, this became so frustrating that when it became clear that we still had a dribble of machine time budget left at the end of these experiments, we set up one more to address that problem specifically, and that will be the last of these posts when I get so far. But for this one I can basically give you only a very simplified set of findings, some of which might address real questions if only we could trust our results, and then gently suggest that even what we did get might justify some careful conclusions, though they might not really have justified the labour. So: some late antique numismatic questions, as answered by the S8TIGER in January 2016!

Bruker S8 TIGER XRF analyser open for business

Our tool of analysis, the S8TIGER WD-XRF machine, ready for action

Our first question in this set of tests was about fractional denominations. Though the primary imperial gold coin was the famous solidus, the “dollar of the Middle Ages”, there were also small numbers of halves (semisses) and thirds (tremisses) struck, with slightly different designs.1 Were these actually struck from the same metal as the solidi? Our results, shaky as they were, suggested that the answer was broadly ‘yes’, at least at Constantinople and, as far as we could test, Carthage. The only place where we picked up any reasonably substantial difference was Syracuse, in Sicily, but we’ll come back to that…

Gold solidus of Emperor Maurice struck at Ravenna 582-602, Barber Institute of Fine Arts B2390

Gold solidus of Emperor Maurice struck at Ravenna 582-602, Barber Institute of Fine Arts B2390

Gold tremissis of Emperor Maurice struck at Ravenna 582-602, Barber Institute of Fine Arts B2391

Gold tremissis of Emperor Maurice struck at Ravenna 582-602, Barber Institute of Fine Arts B2391; note the different design

The other thing we were hoping to establish in this set of tests was variations between mints. I admit that I was cynical about this; as I think I’ve said before, it had sort of become clear that almost all the elements were shared, and that this made sense in a world where imperial coin was being sucked into Constantinople in tax from right across the Mediterranean each year, melted down and then returned to the world as new coins; the recycling should have mixed everything together over time.2 So the only place we had a hope of seeing such variation was in places where that centralisation was breaking down, and in fact, from very early on it had become clear that late coins of Syracuse were gold-poorer than their Constantinpolitan contemporaries, to the extent where the one of us who hadn’t loaded a coin, so didn’t know what it was, could still tell if it was a Syracusan one from its results.

Graph of gold content over time for Byzantine mints of Constantinople and Syracuse

A very rough Excel-generated graph of coins’ gold content over time for the mints of Constantinople and Syracuse, by your humble author

Some of that impurity was visible by eye, indeed, but we could pick it up from before that. Indeed, there are one or two problem cases where mint attribution is uncertain for such coins, and for one of those at least, we were pretty sure we could now partly answer the question.3

Powerpoint slide showing three tremisses of Emperors Leo III and Constantine V from different mints

This is a slide I’ve grabbed from a presentation I will come to tell you more about in Princeton, and it’s the one on the right that’s the undecided case; but its metal content is much more Italian than Constantinopolitan, and we might get further yet

Why Syracuse was allowed to run its coins differently is a separate question, since as far as we know it was still paying tax to the centre and its coins must have been detectably poorer there too, but maybe what we’re seeing here is actually proof that it didn’t pay tax; its small change, too, seems to have been treated in such a way as to restrict its circulation, and Rebecca Darley (I can take no credit for this thought) wondered therefore if Sicily was persistent suffering a currency drain to the East that these measures were meant to stop by deprecating the exchangeability of Sicilian money.4 It might have helped!

Scatter plot of silver content versus copper content of Italian-attributed Middle Byzantine coins

Scatter plot of silver content versus copper content of Italian-attributed Middle Byzantine coins, which is probably Maria Vrij’s work, though I don’t remember; it was certainly her idea to do it

But as it turned out, we could get one step further with such distinctions. One of the other enigmas about coinage in Byzantine Italy is that we’re not totally sure which issues belong at which mints. Syracuse’s particular characteristics become distinctive after a while, but there are a rook of issues which are tentatively attributed to Ravenna, Rome or just ‘Italy’ that no-one’s really sure about.5 We haven’t solved this problem, but we may have spotted something that will help with it. I say ‘we’, but just as I owed the previous point to Rebecca Darley, this one was thought of by Maria Vrij; I sometimes think my sole intellectual contribution to this project was mainly defeatism. Maria noticed that whereas the Syracuse coins were debased with both silver and copper, and thus maintained a ruddy gold colour even once quite poor-quality, the elemental profile we were getting from supposed Ravenna issues included nothing like as much copper. Instead, the Ravenna issues seem to have turned ‘pale’, being adulerated only with silver. In that respect, they were following the trend of the post-Roman West at large, but it also makes sense in its own terms: Ravenna issued silver coin, which Syracuse didn’t, so when they had to cut corners with the solidi it makes sense that it was the refined silver from the local coinage that went into the pot, while Syracuse was presumably using less processed metal with accompanying copper content.6 So that’s something that belongs to Maria to write up properly, but hopefully it won’t be as many years before that happens as it has already been since we found it out… I make no promises there, as we all have other priorities, but nonetheless, we did find stuff in these tests that people might want to be able to refer to, and I hope this write-up at least gives some basis to believe that!


1. If you want the basics on these coinages, you can do no better even now than consult Philip Grierson, Byzantine Coins (London 1982), where pp. 50-56 will cover you for these purposes. The catchphrase, though, comes from Robert Sabatino Lopez, “The Dollar of the Middle Ages” in Journal of Economic History Vol. 11 (Cambridge 1951), pp. 209–234, online at http://www.jstor.org/stable/2113933.

2. My picture of this process comes pretty much direct from M. F. Hendy, “Aspects of Coin Production and Fiscal Administration in the Late Roman and Early Byzantine Period” in Numismatic Chronicle 7th Series Vol. 12 (London 1972), pp. 117–139, which is clearer than his later treatment in Michael Hendy, Studies in the Byzantine Monetary Economy, c.300-1450 (Cambridge 1985), pp. 257-303.

3. The standard reference for such matters, Philip Grierson, Catalogue of the Byzantine Coins in the Dumbarton Oaks Collection and in the Whittemore Collection, volume three: Leo III to Nicephorus III, 717—1081 (Washington DC 1973), Part I, where the coins in question are listed under Leo III 18a.1 (the Barber’s specimen online here), 48 (the Barber’s specimen online here) and, maybe, 12, 13 or 42 depending on what the Barber’s specimen (online here) actually is; the metallurgy makes type 42 seem likely though!

4. On the relevant Sicilian small change see for basics Grierson, Byzantine Coins, pp. 166-168, but for a different view of what was going on with its currency see Cécile Morrisson, “Nouvelles recherches sur l’histoire monétaire byzantine : évolution comparée de la monnaie d’or à Constantinople et dans les provinces d’Afrique et de Sicile” in Jahrbuch der österreichischen Byzantinistik Vol. 33 (Wien 1983), pp. 267-286, repr. in Morrisson, Monnaie et finances à Byzance : Analyses et techniques, Collected Studies 461 (Aldershot 1994), chapter X.

5. Grierson, Byzantine Coins, pp. 168-171.

6. Ravenna’s silver is discussed ibid., p. 140, but for the bigger picture see Mark Blackburn, “Money and Coinage” in Paul Fouracre (ed.), The New Cambridge Medieval History volume I c. 500‒c. 700 (Cambridge 2005), pp. 660–674.

2 responses to “All That Glitters, Experiment 6 and final

  1. Pingback: Some reasonable mitigation | A Corner of Tenth-Century Europe

  2. Pingback: All that Glitters 7: the slight return | A Corner of Tenth-Century Europe

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