Crystallized? Fouree? Very lightweight Ptolemaic tetradrachm

[CPK]

Hello my fellow Numis Forvm members,

Recently I was able to pick up a bucket list coin which I never thought I'd own - a Ptolemaic tetradrachm with the deified Alexander. Now it had some clear issues - a large chunk missing from the obverse, not to mention scratches across the portrait - but it's not too bad, and I was able to buy it with an offer of about 1/10 what a decent one would normally bring, so I decided to risk it.

The seller did not list weight and I was curious where it would come in. Yesterday it arrived and I was able to check. 11.14 grams! I was expecting it to be low-ish what with the defect but wow, that's light. So now I'm trying to figure out why.

The planchet flaw on the obverse may account for a gram or so, but that still means it's a good 2-3 grams (10-20%) underweight.

I thought it might be a fouree, because you can also see what look like surface cracks on the obverse, but I think I may have found a reverse die match here on ACSearch, which would indicate it's an official issue.

The interior of the coin as visible through the defect looks to be brittle and somewhat crumbly. Could crystallization account for that much weight loss?

Looking for some expert opinions here! Worst case scenario would be a modern fake, but I don't think it is. If fouree I might look into returning it. I can live with crystallization, like I said it was relatively inexpensive and I'm happy to have been able to get a specimen at all!

I should add that there isn't anything suspicious about the edge that I can see, e.g. casting seam, filing, etc.

 

and the possible reverse die-match from ACSearch:

 

Any light you can shed on my question would be greatly appreciated!

 

[Deinomenid]

I do not have any data on crystallization weight loss ranges but when I had a similar situation I saw an old  post (2013) from dougsmit saying that 40% loss of weight was  possible. Or  rather someone asked if 40% loss of weight could be possible from crystallization on a denarius and he said "Yes, it can. Burial in soil can leech away metal and reduce weight. (Cited from: https://www.cointalk.com/threads/ancients-did-my-caracalla-denarius-go-on-a-crystallization-diet.238550/)

On the other question, I have die-matched fourrees from Neapolis, so being die-matched alone doesn't mean  it can't be a fourree. (Unless there's something specific about fourrees and that mint. )

 

 

 

[CPK]

7 hours ago, Deinomenid said:

I do not have any data on crystallization weight loss ranges but when I had a similar situation I saw an old  post (2013) from dougsmit saying that 40% loss of weight was  possible. Or  rather someone asked if 40% loss of weight could be possible from crystallization on a denarius and he said "Yes, it can. Burial in soil can leech away metal and reduce weight. (Cited from: https://www.cointalk.com/threads/ancients-did-my-caracalla-denarius-go-on-a-crystallization-diet.238550/)

On the other question, I have die-matched fourrees from Neapolis, so being die-matched alone doesn't mean  it can't be a fourree. (Unless there's something specific about fourrees and that mint. )

 

 

 

Thanks for the reply. I am leaning towards it being crystallized, rather than plated. First of all it's almost too light for a fouree. A copper fouree should still weigh about 13-14 grams. Silver crystallization, on the other hand, could in theory (assuming 40%) reduce the weight to as little as 9-10 grams. 

Second, the interior of the coin - visible through the large chip on the obverse - shows some of the same silver/white look that the unbroken surface has, which wouldn't be the case with a plated coin. Part of the interior also has a darker, granular look which resembles some pictures of crystallized coins I've seen.

Additionally, the unbroken surfaces have that "blasted" look you often see with crystallization.

Anyone else have any thoughts?

[AussieCollector]

Also think crystallized, rather than plated - for the precise reason you listed. The missing chunk looks exactly like it should for a crystallized coin.

But, I am no expert.

I'd also note that this is why I never buy underweight or unknown weight coins - being underweight drives me crazy with the "but what if?" question.

Edited August 12, 2023 by AussieCollector

[Nerosmyfavorite68]

Congratulations on picking up a cool type!

I'm no expert but I'd vote crystallized, just from personal observations.

Here's a couple of crytallized coins of my own, one with spalling, one whole.  Bactrian coins seem prone to crystallization.  The soil there?

 

19MM . 2.86GM

Laureate head right, with slight drapery on far shoulder / Minerva standing right, holding reversed spear and leaning upon round shield, both set on ground. RIC II 330  

Menander

Attribution: MACW 1782
Date: 160-145 BC
Obverse: Helmeted head of Menander right
Reverse: Athena advancing left with raised shield, brandishing thunderbolt
Size: 14.37mm
Weight: 0.90 grams