Discussion in 'Ancient Coins' started by Neal, Dec 14, 2017.
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I came across this article which looks very basic but which might start you off in the right direction for study.
@Valentinian can make sense of it...
The government issued coins with some lead in them. Cope analyzed many tetrarchal and Constantinian-era coins and some had over 10-12% lead. Sometimes the lead mixed well, sometimes not. It is small percentage of coins that dramatically show when the mixing was poor. When a glob a lead was in the flan, sometimes it corroded away. (Usually in the process it turns white first.)
This is one of the finest coins I have seen with obvious lead globs. It is an AE30 Diadumenian (217-218) from Laodicea ad Mare in Seleucia Pieria. At 11:00 on the obverse and elsewhere you can see the white and empty pockets where lead was and is now missing.
I think the explanation of the OP coin is that it was made of poor metal with some lead globs in it, which, over time, corroded away. The fact that particular example had lead in the center is coincidental.
Interesting, and a look like that, I would assume its a form of BD, even though it isn't green.
The white occlusions on this coin are lead and have the look of oxidized lead as opposed to BD.
It does not have the characteristics of BD. It is just the lead component corroding and sometimes falling out of the coin.
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