I have a question for anyone who knows much about patina on ancient coins. I know that the kind of soil and mineral content would cause a coin to develop different shades of patina. I have some ancient Roman coins with heavy patina...some are dark green, a lighter shade sort of lime green, and a personal favorite is a medium tan patina. Can anyone explain to me what causes the different color patinas and what kinds of soil would cause this color versus that color? Any information would be appreciated!
I would also be interested if someone could elaborate more on this topic. I'm rather sure that indeed mineral content, pH, chemical composition, gas content (oxygen, etc.), and the coin metals/alloys themselves would play roles...
I believe alot of these coins when removed from the ground,are preserved in professional ways,and it depends on the material used to preserve them.which leaves the specific patina.
The main difference in the desert patina seems to be the presence of a comparatively high concentration of Silicon along with Chloride in a very dry environment for hundreds or thousands of years. The blues and greens ( verdigris) seem to start out similar to modern ( 200 years or so) copper/silver types of coins, but over the extended time period, layers of different composition patina develops over the original. But as with many subjects of antiquity, there are different theories. Bad Thad has done a lot of research on modern verdigris composition for his upcoming book, and maybe he will expand into ancients also. Jim
