• CORRECTION: On Aug. 15, 2016, this graphic was updated to correct the year when the penny acquired its current composition. It was 1982, not 1984. Also, the graphic was updated to reflect that coins are struck from planchets (not cast from molten metal) and some (not all) dollar coins produced between 1849 and 1889 contained 90% gold.
Volume 94 Issue 28 | p. 29
Issue Date: July 11, 2016

Periodic graphics: the compositions of U.S. coins

Chemical educator and Compound Interest blogger Andy Brunning shares some fun facts about the metals in pennies, nickels, dimes, and quarters
By Andy Brunning
Department: Science & Technology
News Channels: Analytical SCENE, Materials SCENE
Keywords: periodic graphics, copper, zinc, nickel, penny, dime, quarter, mint, currency

To download a pdf of this article, visit http://cenm.ag/coins.


To see more of Brunning’s work, go to http://compoundchem.com. To see all of C&EN’s Periodic Graphics, visit http://cenm.ag/periodicgraphics.


This article has been translated into Spanish by Divulgame.org and can be found here.

 
Chemical & Engineering News
ISSN 0009-2347
Copyright © American Chemical Society
Comments
Brian (July 12, 2016 7:29 AM)
The change in composition for pennies was in mid-1982, not 1984
Steve (July 18, 2016 9:13 AM)
Brian, I think that 1982 is correct. That's what the US mint says.

Fun exercise for young students to get a bunch of them and just weigh them to see
differences.
Andy Brunning (July 25, 2016 3:47 AM)
1984 does appear to be a mistake. The graphic will be corrected shortly.
Joe Atkinson (July 19, 2016 7:46 PM)
Why is a variety of metals used for different coins? Why not use the same mixture for all the coins? Pick one which has proven useful and durable. This would surely be less expensive.
Andy Brunning (July 25, 2016 3:46 AM)
I imagine the issue is that coin composition needs to be closely tied to its value, or the likelihood of it being melted down for its metal content increases. More practically, any wholesale changes to currency composition, size, and weight would cost businesses large amounts of money due to the need to replace any machines that operate based on these parameters.

Finally, if all coins had the same composition, they'd become more easy to counterfeit. The US Mint has already ruled out using steel cores for new quarters for this reason. The UK is introducing a new £1 from next year with a more complex composition to try and combat counterfeiters; it's estimated that currently, one in every thirty £1 coins in circulation is a counterfeit.
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