Observations on Nickel Oxidization

Hey Guys!

       So yesterday's post got me thinking about a trend that I have picked up with a number of the older Jefferson nickels, which you can see in the picture below:

The coin I am looking at in question is the 1940 nickel in the middle bottom of the picture.

         As you can see the 1940 nickel stands out from it counterparts because it has this unusual black stuff surround every high point of the design. It particular this black substance surrounds the date and letters on the obverse of the coin, as well as the letters on the reverse.

        After looking on the internet for clues as to what this mystery material is, I believe I have found a likely culprit.

Nickel Oxide in its Processed Form

  

         This charming pile of black is actually a compound known as Nickel Oxide (NiO). It is created when elemental nickel in some form comes in contact with water and then proceeds to deteriorate and form this compound (in essence NiO is the equivalent of rust for a nickel)!

         To prevent nickels from oxidizing the U.S. National Mints actually use the a 75% copper, 25% nickel composition of metals in their nickels. The properties of these two metal combined with a thin protective non-reactive coating over the coin prevents it from oxidizing.

        This would explain why I generally only see nickel oxide on older coins...the decades of circulation have removed the protective coating and allowed the nickel to come in contact with water!

        I hope you all enjoyed this science lesson today! Please leave a comment if I left something out of this explanation!

Have a great day and Happy Collecting!

- Sean