Discoloration on Heraclius gold solidus - what can it be?

Hello,
Can anyone help me about the condition of this gold solidus?
What could be the reason of its discoloration? Is it perhaps a limescale or something other?
How could it be removed? Or should it be removed at all?
Thanks for the help in advance!

 

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There was another thread a day or two ago--sorry, I don't remember what it was about--where someone wrote that the red discoloration could have resulted from being buried in high-sulfur soil. Sorry, that's all I know about it.

 

Before is the quote from a metal detector find thread... I'm not saying that is what it is though, I'm no gold expert

https://www.cointalk.com/threads/fellow-metal-detectorist-find-gold.325045/

 

Nice coin, I like the extra color.

Welcome to cointalk !

John

 

On moderns the red color is the result of a high copper concentration at the surface. I see it as toning.

 

I'm no expert on old gold, but I'd be amazed if leaving it as it is were not the correct answer.

 

Nice coin. I would not try to clean it mechanically as gold is very soft, nor would I go the chemical route (too risky).

 

Elemental gold is inert and will not easily form ions that combine with other elements to form this discoloration. Gold can be dissolved in aqua regia -- a mixture of nitric and hydrochloric acids -- but this is unlikely to have happened just sitting in soil.

There are two more likely reasons that a gold coin is discolored:

(1) If the coin was not 100% pure, elemental gold, the non-gold elements on the coin's surface might have oxidized or combined with other elements in the soil to form this toning.

(2) During the striking process, some iron from the die was transferred and imbedded into the surface and this iron has rusted to create the toning.

I believe it's also possible that really difficult-to-remove encrustations have formed on the coin's surface, but this doesn't appear to have happened on this coin.

 

Thank you very much for the answers!
So as I understand, this discoloration is really an unwanted condition. Does it make this coin ugly? And does this phenomenon decrease the value of the coin?

 

True Boscoreale toning on gold coins usually commands a premium over non-toned gold coins. This is because Boscoreale toning is associated with the 69 AD eruption of Vesuvius, one of the most historic events in ancient Rome.

Your coin wasn't in existence during the eruption of Vesuvius, so it's not Boscoreale-toned. If your coin's discoloration can't be removed with water and a clean cloth, there's no point in trying to remove it. It's unlikely to detract from the coin's market value.

 

I like toned gold and think the coin is attractive the way it is.

 

Maybe a little ethyl alcohol or acetate with a cotton swab, but if that doesn't remove it, I wouldn't go any further. Admire it the way it is.

 

I believe (again - no expert) it ENHANCES the coin. Makes it seem more "authentic" to me.

 

I had picked up some "Etruscan" (unlikely but I dunno) gold earrings/decorative items from a collection being liquidated, which appear to be made of electrum and possess distinct red toning in the recesses of the back side.



I was perplexed by the toning and the answer I recall finding is that it is the silver in the gold alloy which can react with substances in the environment and generate a patina/toning on long-interred items which appears red to the naked eye and iridescent under microscope. Can't state it with certainty but I was satisfied with the explanation.

 

I have just found an interesting article about red spots on gold coins:

https://taxfreegold.co.uk/redspotsongoldcoins.html

 

I think it gives the coin ..character, I would leave as is.