what causes this color?

[cnladue]

I have seen several ebay ads lately in which the seller is bragging about the coins beautifull rainbow colours.What the heck is that about?Or they say somthing like mint lusture...well i just thought this one had been ruined by someone before i found it.

[diamond]

Like many copper-plated zinc cents, this one has darkened with time and exposure to oxygen, humidity, and other environmental factors. Some like to use the euphemism "toning". Some coins tone pretty and others, like zinc cents and Sacagawea dollars, tone ugly.

[wavysteps]

I may add that your coin also has "Verdi Gris" (the green looking stuff). Since this is a broad-strike and has some worth over face value, you may want to try and remove the Verdi Gris before it spreads even further. Try dipping the coin into pure acetone (NOT nail polish remover for that has additives) and then taken a cotton swab to the affected areas. Stubborn spots may take a longer time to remove but this can be accomplished with a long (up to a year) bath in mineral oil.

BJ Neff

[cnladue]

oh my ....its like my penny has ringworm or somthing.i always thought mineral oil changes the color too?

[diamond]

Do NOT use acetone on zinc cents. It makes any surface contamination turn green. Then you have to mechanically remove it with a toothpick. I have no experience with mineral oil.

[Kuriouskoinkat]

Rainbow toned..

I was told there are a few kinds of toning like that.. Natural Toned,, Enviormental damage.. Or I have heard They can dipped with something.. I have of bunch shiney copper rainbows. Almost like proof.. A local dealer said enviormental Damage...... Then a Error-Variety expert told me they were natural.. They also came from the middle of rolls. vs. the end ones most likely are NOT natural.....Don't quote me. I'm not an expert. I was taught this....I could have been told wrong.

[diamond]

I haven't delved into the subject of toning with any depth or enthusiasm. I don't like toning, but sometimes it's unavoidable. And it's better than a coin that's been cleaned. Even toning is more attractive than blotchy or spotty toning. Rainbow toning is garish to my eyes, but some folks love it. It is possible to accelerate toning and that's referred to as artificial toning. I don't know if anyone is truly able to reliably distinguish between natural toning and artificial toning.

[magusxxx]

Here's a rainbow cent I found in change about a month ago.

[Kuriouskoinkat]

Rainbow toned..

rainbow.jpg

Does this look like a rainbow toned to anyone ?? 1960 lincoln cent

[coin detective]

lincoln cent toning

I find coins toned like this all the time while metal detecting in water. its caused by the variety of gases given off by decaying matter.