A compositional analysis of silver Roman imperial coins using XRF

I've done weighing of coins but never s.g. Even for simple weighing I've found it necessary to buy a Ohaus Analytical scale. The usual $99 digital jewelers' scales are simply not accurate. They will show a small coin as being lighter and a heavy coin as weighing more than they should. Thus it's not just calibrating to a single value to get the correct weight, but the weighing behavior of common commercial scales is not linear.

I have a certified ASTM weight set for calibration. These are not too expensive depending on the accuracy desired ($20 or $40 for .01 or .001 gm I recall). They get more $ for a higher accuracy

Now if the weight is off even a little, the s.g. could be off by a huge %. The problem is that the densities of pure copper and silver are "relatively" close to each other. It'd be better if they used an Iridium/ Aluminum alloy but such is life. Also I can't find evidence of the use of scientific method in your paper. Have you done any further checks?

 

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Babbitt metal appears to be largely tin (Sn) + other metals: maybe lead or copper. If largely tin, that metal is quite light 7.31 g/cc while silver is heavier 10.49 g/cc. Lead is even heavier tho 11.29. But if largely Sn I expect a Babbitt metal specimen to be appreciably lighter.

Why I followed this thread is that I just got my 2nd weird late Roman higher grade siliqua. This is a Constantine III (409-411 AD) following up on a superb Jovinus bought 2-3 years ago. I'd love to do an XRF on both pieces.


Constantine III (co-Emperor in Northern? Gaul) silver siliqua 409 - 411 AD
ex-Gorny & Mosch


Jovinus (another usurper) silver siliqua 411- 413 AD

I'm going to have to stop myself from buying these odd ball siliqua and buy some nice regular coinage for a change!

 

I just looked at the section on Roman siliqua as quite recently I just bought my 3rd example of this denomination (see above). All 3 are in nice grade.

His graph on the siliquae lists a Theodosius III. There is no Roman Emperor of that name; he would be a Byzantine Emperor of the 8th century AD. I think he meant to type Theodosius II.

Similarly Julian II was Syriac Orthodox patriarch of Antioch 688–708. I believe he meant Julian, who was an emperor 360-363 AD, who commonly minted a lot of siliquae.

Another question I have is that he apparently indicated that the siliquae of Valens are made of a Tin/ Antimony mixture. This is misleading as I believe many good silver siliquae of Valens exist. He simply encountered a contemporary counterfeit as in nature, Antimony (Sb) is often encountered mixed with Tin (Sn). This counterfeit should've been excluded from the analysis.

Here is my siliqua of Valens: (also the 3rd of my 3 siliquae)

(Stack's: Coin Galleries, mail bid, lot 866, July 2007)

It was relatively cheap then. I simply wanted a Valens and had a couple to pick from. No serious competition.
It doesn't appear to be tin at all.
note: ancients were often not slabbed back in 2007.

A correction to my above post on Constantine III. The dates could be 407-411 AD. Con-3 was co-Emperor with Honorius, however, from 409. Previously he was a general who declared himself Emperor in {Northern?} Gaul in 407.

 

Pretty sure that everybody calls Julian the Apostate, Julian II, or simply Julian.

Although Julian II may have also been a later figure, many collectors seem to consider the first numbered Julian as Julian of Pannonia (Julian I), and the apostate as Julian II.

 

Okay thanks @hotwheelsearl . I was unfamiliar with Julian of Pannonia until now. Another usurper I should get from a tough time period (mid 3rd century AD). I never call him Julian the Apostate as he embraced the original Roman theology although one can also say that since Christianity was the official religion of Rome, he was Apostate against that.

Having read Gore Vidal's book {highly recommended BTW}, I refer to him as "Julian the Philosopher".

I'd really love to do an XFR analysis of my siliquae and add them to that study.