Desert patina….on a quarter?

[mr. wiggles]

I hope I can be forgiven as this isn’t truely ancient coin related, and is likely an affront to those who enjoy modern coinage.
 

One of the things I’ve been interested in has been the patina that forms on coins, the natural process and time that this all takes. This spring I was out with my kids on a walk at a park and I spotted the quarter below.

I was struck how similar this looked to the desert patina we see on bronze coins. My interest was piqued, and my inner scientist wanted to conduct an experiment. I wondered how long this quarter sat before the patina developed, was it a few months or a few years?  So I scooped up some dirt from the same spot, brought it home and set it outside in a cup with a “new” quarter. Occasionally I’d add a little water and let it drain out. I left the quarter out there maybe 3 months and you can see that it looks a lot like the first quarter I found. Naturally, the conditions are different from a desert, but I was surprised how quickly this look developed!

 

Anyone find any similar modern coins with “ancient” seeming patinas? Or any thoughts on how long the desert patina took to form on Roman coins?

Edited October 11, 2024 by mr. wiggles

[John Conduitt]

I would think there is a difference between patina (where the metal reacts with the elements it comes into contact with) and deposits. 'Desert patina' is therefore not patina at all. Presumably some sort of adhesion could occur almost immediately if a coin was dropped in something like concrete. Patina can also form quickly in certain conditions but requires a chemical reaction and can take a very long time to go through all the stages, since the initial reaction protects the coin underneath.

Edited October 11, 2024 by John Conduitt

[Dafydd]

This is an interesting observation and there are many, many debates on patination.

Dig deep on this forum and you will find many opinions. 
 

However, your comments are erudite and you will really enjoy your journey here.

[Dafydd]

Oh by the way, only the ignorant take offence.