Lincoln Blue-Green Toning Happens

Why are they rare?
I have seem them often enough to not give them a second thought. Copper naturally discolors like that.
I'm intriqued.

I must be.

Really? Show me an example please.

I can tell you these coins have never been exposed to that. I pulled these from circulation....and they wouldn't even be worth the trouble.

The MS70 treated coins are actually bluish-purple on a red copper, not greenish.
I will try to find some from my experiments a few months ago. The trick is to get it on camera.

The reason they are rare is primarily due to the movement of the coinage. Light layers of Cupric Sulfates or Sulfites do not have time to accumulate so mostly wears off. And then too, the coin has to be exposed to the proper amount of moisture, Oxygen, Sulfur Oxides, etc and for a specific amount of time. In our chem labs we make Cupric Sulfate that has that excessively blue color but rarely on coins.
So Thad, just were did you get those anyway. Or did you make them? That 78 and 93 really looks like an artist rendition of a blue painting. Now if you contact the Franklin Mint you might want to have them produce some plates like that.
I've been collecting for well over 60 years now and only seen a few like that. Maybe not quite that blue, but a little like that.

Carl - The first two I pulled out of my pocket at the end of the day, lucky circulation finds. The 1956 I found at a local coin shop....it kind of stood out amongst the others in the box. LOL

I've fiddled around in the lab with AT before, but with ZERO luck. All I managed to do is turn cents black or just plain ugly. LOL

I wish I wasn't color blind. I'd probably enjoy this thread a lot more.

I've found alot of those as well recently - probably 25 or so. I didn't think they were uncommon.
i wonder what conditions cause it naturally?...i guess its black oxide.