| Author |
 Replies: 65 / Views: 40,186 |
|
|
|
|
Bedrock of the Community
United States
62064 Posts |
You can see the copper on your coin. Just a poor plating job. The coin was copper, then poorly plated. Now it is showing the copper color in spots. The weight would be normal for a copper cent. 3.14 grams. Note the weight on an aluminum cent. .93 grams.
|
|
New Member
United States
16 Posts |
Yes, you were right, its 3 grams-ish. Thanks for the expertise.
|
|
New Member
United States
4 Posts |
|
|
Pillar of the Community
United States
2775 Posts |
Quote:
I called a local coin dealer who told me there is NO WAY you have a 1978 penny that is silver in color. I took it in and showed him. He wanted to buy it from me, but I wouldnt sell it to him.  Did you or the local coin shop dealer weight the coin? Most likely plated after strike. Weight would shed more light. Thanks, Doug. Edited by Halo1st
04/26/2017 6:58 pm
|
|
Pillar of the Community
United States
1609 Posts |
Well, if we do some simple division, we find that this penny is about 61% the weight of a normal penny, compared to about 29% for an aluminum cent. It's obviously not an aluminum cent. Though seriously unlikely, pure metallic Arsenic has a density withing 1/50 gram per cubic centimeter of what this mystery metal is. Calculations: 1.9 divided by 0.9 (weight of this penny divided by the weight of an aluminum penny) = 2.111(repeating decimal). Density of aluminum = 2.7 g/cm cubed. 2.7 * 2.111 = 5.7 g/cm cubed. Density of arsenic: 5.72 g/cm cubed. Really really really really unlikely, but the math pretty much works out.
|
|
Bedrock of the Community
Australia
21788 Posts |
It would be possible for a silver plated planchet to weigh 1.9 grams be of equal thickness AND diameter to a genuine common penny, but the white metal alloy would need a specific gravity of about 5.5 grams / cc.
There a number of metallic elements that would need to be alloyable with aluminum at the right percentage mix, to achieve this result of 5.5 grams / cc.
Either some error has been made in the measurement of weight and diameter, or such an alloy as postulated above has to be used.
XRF analysis of some of the core may give some result, but that would require a deep scratch in the coin to get at the core.
There are much more sophisticated non destructive approaches to core analysis but perhaps the coin may have to be sent to the U.S. Mint to get to the truth.
|
|
Bedrock of the Community
United States
62064 Posts |
That would make a good subject for a new thread. "Gravity Test." I hear a lot about it, but know nothing except term. So that would be a great thread topic for those who know something about the subject.
Edited by coop
04/27/2017 1:21 pm
|
|
Moderator
 United States
189222 Posts |
Quote:
That would make a good subject for a new thread. "Gravity Test." I hear a lot about it, but know nothing except term. So that would be a great thread topic for those who know something about the subject. Two very old threads... http://goccf.com/t/39666http://goccf.com/t/40733 |
|
Bedrock of the Community
United States
62064 Posts |
Kind of an interesting read, but left me with a headache. Seems too technical for me. But now I have an idea how it is done.
|
|
Pillar of the Community
United States
2775 Posts |
|
|
Pillar of the Community
United States
715 Posts |
I feel like it's worthwhile to point out that if you are going to take the volume of the coin by placing it in water, it's best to use distilled water to keep surface reactions to a minimum. It would be a shame to damage this coin if it really is something special. I am really hoping we find out the story behind this mystery. Very curious.
|
|
New Member
United States
1 Posts |
|
|
Bedrock of the Community
United States
62064 Posts |
Looks like a plated coin. Some plating companies do this to show off their work. Ruins collector value. Coin is now altered.
|
|
Moderator
United States
189222 Posts |
Well, it is still worth a cent, but I would keep it as a curiosity. I have a few plated cents I have found over the years. to the Community, Shawnathan1991! |
|
Pillar of the Community
United States
634 Posts |
Of the coins to be ruined, a '78 penny is not bad at all. In fact, I like finding plated cents, provided they're common. I'm hoarding a few.
|
|
|
Replies: 65 / Views: 40,186 |
|
First Page
Previous Page
Posted 01/12/2017 1:28 pm
