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Blue Quarters?


Q. I'm sorry to bother you with this but I have a 2022 Wilma Mankiller quarter that I found in my search. I collect coins myself and am confused a little. I have a bluish color that reflects in the light along the bottom obverse side along the edge! I did nothing to it except try and wipe it off! But it actually part of the coin! Can't you explain please?
Will I AM
- Clarendon,pa
November 20, 2022

Ed. note: When in Rome ...
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Closely related historical posts, oldest first ...

Q. I am doing research for a children's magazine. The article I am writing concerns metallic content of various coins past and present.

I have observed an interesting phenomenon. If quarters are left in water with pennies, all 1999 quarters turn blue. All quarters minted prior to 1999 do not. The U.S. Mint claims that the materials haven't changed. Allegedly, the current quarters still contain the same percentage of metals, 8.33% nickel, the balance copper.

Should I believe the U.S. Mint?

Does anyone have an explanation for the blue quarters?
Thomas J. Barstow
- Great Barrington, Massachusetts

A. An experiment is worth a thousand guesses/opinions, so believe your results. However, a variable that you may not be taking into account is oils and tarnish on the older quarters that may be impeding the reaction. Scrub some old ones with a toothbrush and vinegar and salt, foul the new ones with butter or bacon grease, then put them all through the same cleaning regimen. Good luck.
Ted Mooney, finishing.com
Ted Mooney, P.E.
Striving to live Aloha
finishing.com - Pine Beach, New Jersey

Q. Why do I have an '89 that is blue?
Phil Garcia
- Jax beach Florida
November 13, 2022

A. Looks like Thomas' experiment was not conclusive, and other cupro-nickel clad quarters can turn blue in water.
Luck & Regards,
pic of Ted Mooney
Ted Mooney, P.E. RET
Striving to live Aloha
finishing.com - Pine Beach, New Jersey

To minimize searching & thrashing, multiple threads were merged; please forgive repetition, chronology errors, or disrespect of other responses (they probably weren't there) :-)

What is the greenish-blue sand like substance from a quarter, dime and penny in saltwater

Q. Hello,

I'm in 6th grade and performing an experience to determine if US coins rust faster in saltwater or tap water. I quickly realized that this was a trick question because US coins do not contain iron so they do not rust, however they can corrode. Ten days into my experiment in which I placed a quarter, nickel and penny in saltwater, I noticed a greenish-blue substance, which looked liked sand, on the bottom of the containers holding the coins and the saltwater. I'm curious, which coin combines with saltwater to produce this greenish-blue substance and what is the greenish-blue substance/particles? My guess is the particles are part of the copper corrosion process.
Tommy C. [last name of student deleted for privacy]
Student - Spencerport, New York

A. Tommy,
Why not conduct a search of US coins on the internet to see exactly how each coin is made? Split up the coins and run separate experiments on each denomination. By doing this the teacher can't say "how do you know the greenish- blue salt didn't come from the nickel or dime?" You are on the right track with the penny though.
Mark Baker
Process Engineer - Syracuse, New York

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