Copper or zinc??

[playdan1]

How do you tell the difference between copper and zinc pennies? With a magnet? I tried that, but it doesn't work so well. Any ideas?

 

[idahotokens]

Assuming you are asking about Lincoln Memorial cents, they were made of a copper alloy until during the year 1982 when the composition was changed to copper-plated zinc. The copper cents weigh 3.11 grams and the copper-plated zinc ones weigh 2.5 grams. So, except for the 1982 year when both were made, you can tell by date. For 1982 you could use a postal scale to weigh them, or make a simple balance beam using known copper and copper-plated zinc ones to tell.
John in ID

 

[mick56]

I made a balance beam.

 

[diggummup]

I made a balance beam.

 

[mts]

Don't forget to also try using your metal detector to tell the difference. Some metal detectors have good enough discrimination to where they can tell the difference between a zinc and copper cent. Mine gives a low tone for zinc and a high tone for copper when the discrimination is turned all the way up. It sure beats weighing them or date checking. Just pass them across the coil and you have your answer.

Just for completeness, I'll throw out another alternative method (that I never use). If you bounce them off of a hard surface the copper ones have a nice ring while the zinc ones sound almost like plastic.

 

[MIhunter]

Best bet is too buy a scale, I found one on amazon.com for $6. 95% Coppers weigh 3.1 gm and Zincs weigh 2.5gm!!

 

[saltyshark2002]

Zinc pennies that have been in the ground for a while develop corrosion pit holes when cleaned with a hot peroxide bath

 

[Emperor Findus Cladius]

Don't forget to also try using your metal detector to tell the difference. Some metal detectors have good enough discrimination to where they can tell the difference between a zinc and copper cent. Mine gives a low tone for zinc and a high tone for copper when the discrimination is turned all the way up. It sure beats weighing them or date checking. Just pass them across the coil and you have your answer.

Just for completeness, I'll throw out another alternative method (that I never use). If you bounce them off of a hard surface the copper ones have a nice ring while the zinc ones sound almost like plastic.

Bingo, I use my detector. I will save a bunch of 82's and turn on my machine. High tones go in one jar and low tones in another. Very accurate.

 

[mts]

Don't forget to also try using your metal detector to tell the difference. Some metal detectors have good enough discrimination to where they can tell the difference between a zinc and copper cent. Mine gives a low tone for zinc and a high tone for copper when the discrimination is turned all the way up. It sure beats weighing them or date checking. Just pass them across the coil and you have your answer.

Just for completeness, I'll throw out another alternative method (that I never use). If you bounce them off of a hard surface the copper ones have a nice ring while the zinc ones sound almost like plastic.

Bingo, I use my detector. I will save a bunch of 82's and turn on my machine. High tones go in one jar and low tones in another. Very accurate.

I use my detector on all of them rather than just the 82's. My eyes aren't good enough to date check anymore. Plus, I'm just looking for copper vs. zinc. I don't really care about finding wide AM's and such. My procedure is to look at the back, if it is a wheatie or Canadian (anything but a memorial cent) I throw it into a separate pile. Memorial cents get waved across the coil. Low sound means it's zinc and goes in the reject bin. High tone means that it is copper and goes in the save pile. 100% accurate and very fast. Not as fast as a Ryedale but considering it costs me nothing, I'll live with it.

One thing I'll note is that on my particular detector, very old (pre-1920) wheaties sound off as a broken tone with both high and low components meaning that their composition appears to the detector to be in between copper and zinc. It is very distinctive. But I'm not willing to risk loosing the old wheaties by relying on my ears. That's why I always physically check the back of the cent before passing it over the coil. Once I've visually determined that a coin is indeed a memorial cent, I rely on the detector to tell me its composition.