Numismatic and History Discussion Forums > Coin Photography, Conservation and Storage

Sestertius with green incrustations - BD or verdigris?

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Miguel P:
Hi everyone,

I recently purchased a nice Antoninus Pius sestertius with this kind of green copper compoud in some areas around the edge. Does it look like stable incrustations or should I worry?

They are pretty hard and they are raised above the surface of the metal. However, I'm still concerned so I would like to know your opinion.

Thank you very much in advance!

Akropolis:
Looks mostly stable, but poke light green areas with a wooden toothpick. If powdery green comes off, you have BD.
PeteB

Miguel P:
Thanks for your reply!

I poked a little and brushed it gently with small (unused) toothbrush, but couldn't see any powder come off. Should it still be recommended to remove these incrustations though?

Akropolis:
If stable, and I think they are, do NOT remove them. You will probably destroy the coin in the process.
PeteB

Miguel P:
Thanks, I will not attempt to remove it.

I took another shot  with better lighting and it seems to confirm that they are stable malachite/copper hydroxi-carbonate crystalline incrustations (they are also very hard) I used gloves to prevent any chloride ions present in my sweat from coming into contact with the coin.

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