Crystals on coin Surface

Summary of discussion on CoinForgeryDiscussionList
Date:  Sun Jun 24, 2001  8:33 pm
Subject:  small crytals on coin surface what do they represent ?

I have been looking at some struck copper coins I assume are 
ancient under 17X magnification I can see small crystals on the
side in the crevices. What do they represent, a nice uncleaned
coin or something else I should worry about.

The term "Toning" I assume is used for the change of color of
the surface of the metal and different in character to the
growth crystal, which could not have existed just after a coin 
was struck 

Thanks for any advice or clarification.  I wish there was a 
website with high resolution images of these different results
of real or forged aging.

From: Date: Sun Jun 24, 2001 10:04 pm Such crystals are fairly common on authentic coins. They are also fairly common in certain types of rocks, some quite recently formed, where there is a lot of thermal activity or highly saturated water percolation, or boiling. Metal is leached out of the coin into solution (such as ground water with carbonic and humic acid in it). The water hangs around, until the rain or other source goes away or diminishes. Then the water starts to evaporate. As it does, it becomes super satured (can not carry all the metal salts or even elemental metal in solution), so it dumps metal onto the surfaces of the coins. This tends to happen in cracks because they will often have more water, where the outside surface can be more sealed in with fine mud (if water was flowing through very easily, and drying very fast, I doubt this would happen). Or similar crystals on the surface of the coin are removed when the coin is cleaned. Tiny nuclei come out of solution or are recruited from microscopic bits already present, and you get the standard process as seen in nature often (such as in metal ores). Such processes are of interest as they can be hard to imitate, especially if you get to know how they should look. Easy enough to put crystals of metal on a coin, and it could even be a byproduct of cleaning processes. I have seen it happen when a cleaning solution loaded with metal salts dries up over periods of months. I suspect processes occuring over centuries will be quite distinct from those occuring over months in the crystalline morphology and other characteristics. Copper crystals seem to be the most common type, even in silver coins. This would be a complex study, and require a lot of study and review on my part to accomplish much. Still instinct and experience can be usefull I think with such secondary growths on coins, to distinguish forgeries from real coins. Most forgeries, if they pretend to be cleaned at all, are not cleaned over long periods. The forger is usually anxious to get them to market, as unlike if he had real coins, he has something of no real value he wishes to profit from, not something he might speculate in and hold for some longer period.
From: - Mike S Date: Mon Jun 25, 2001 8:54 pm Electrolytic and even chemical removal of the hard red and green patina/encrustations that often form on the surface of debased silver such as the tetradrachms of Antonine era Egypt can result in copper metal deposits/patches of substantial thickness on the surface. Hence, fully metallic (yet ancient) copper can potentially be found on authentic silver coins as the result of ill advised cleaning attempts. Once done, it is extremely difficult to remove it without damaging the coin as well. (Yes, for the record, I have learned both these things the hard way!)