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Lemon Thrower
1000+ Penny Miser Member
USA
1588 Posts |
 Posted - 11/22/2009 : 08:11:29
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Gold filled with tungsten has been in the news lately.
Is there a reliable way for the average joe to test gold coins to ensure they are pure? of course one can measure the mass with a scale and the volume using calibers and comparing the measurements to official specifications, but the weight of tungsten is so close to gold's that these simple measurements probably would not catch a fake.
is there a way to rig up a coin comparator to test a sample coin based on a legit coin?
how much does an off the shelf comparator cost?
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Buying:
Peace/Morgan G+ at $15.00
copper cents at 1.3X
wheat pennies at 3X
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brian0918
Penny Collector Member
USA
315 Posts |
Posted - 11/22/2009 : 11:10:45
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| Assuming that they're just sticking a tungsten clump inside a thin gold casing, couldn't you just do the ring test? A coin with an outside of gold and inside of tungsten is not going to sound the same as a pure gold coin. The clarity of the sound depends on the atoms being in a lattice, and there isn't going to be any metallic bonding between a gold casing and a tungsten core, so it should just dull the sound or cut the ring short as the vibrations are inefficiently transmitted between the two metals. |
"The man who speaks to you of sacrifice, speaks of slaves and masters. And intends to be the master." -- Ayn Rand
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Edited by - brian0918 on 11/22/2009 14:00:01 |
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HoardCopperByTheTon
Administrator
USA
6807 Posts |
Posted - 11/22/2009 : 11:38:48
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I agree with Brian.. a tungsten core would not ring true. Think about how a zinc core penny sounds when you ring it.
For smaller gold coins you could just use your Ryedale with another example of the coin your are testing as a sample coin in the comparitor.  |
If your percentages are low.. just sort more. If your percentages are high.. just sort more.
Now selling Copper pennies. 1.6x plus shipping. Limited amounts available. |
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1945V
Penny Pincher Member
Canada
153 Posts |
Posted - 11/22/2009 : 14:11:23
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Pencilvanian provided a weblink for how tungsten can be detected in the silver bullion forum.
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The method sounds expensive and complicated, but if it works then it will be very popular among those who wish to verify the purity of their gold.
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Lemon Thrower
1000+ Penny Miser Member
USA
1588 Posts |
Posted - 11/22/2009 : 14:32:21
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quote:
Originally posted by 1945V
Pencilvanian provided a weblink for how tungsten can be detected in the silver bullion forum.
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You must be logged in to see this link.
The method sounds expensive and complicated, but if it works then it will be very popular among those who wish to verify the purity of their gold.
i do not see his explanation at that link |
Buying:
Peace/Morgan G+ at $15.00
copper cents at 1.3X
wheat pennies at 3X
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IndieScience
Penny Sorter Member
33 Posts |
Posted - 11/22/2009 : 14:40:49
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| I don't know if you could use the ryedale since it is very sensitive to mass and paramagnetism. Seems likely that each small coin, regardless could end up going into the same slot. |
Check out my Science Website: http://www.indiescience.org |
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pencilvanian
1000+ Penny Miser Member
USA
2209 Posts |
Posted - 11/23/2009 : 19:03:10
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Just to clarify-
I did not post the explanation on that link, I just found that link offering different ideas to determine real gold from tungsten filled gold.
Explanation found-
"Gold is diamagnetic, tungsten paramagnetic. That difference could be used to detect tungsten too; but a simple magnet does NOT detect tungsten"
Diamagnetism appears in all materials, and is the tendency of a material to oppose an applied magnetic field, and therefore, to be repelled by a magnetic field. However, in a material with paramagnetic properties (that is, with a tendency to enhance an external magnetic field), the paramagnetic behavior dominates You must be logged in to see this link.
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pencilvanian
1000+ Penny Miser Member
USA
2209 Posts |
Posted - 11/23/2009 : 19:20:06
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You must be logged in to see this link.
Gold-2.5 - 3.0
Tungsten 7.5 - 8.0
Copper penny 3.2 - 3.5 (a bit of trivia for copper cent fans out there)
Tungsten is a brittle metal, gold a malleable metal.
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Maybe this is the answer-
You must be logged in to see this link.
Testing the resistance differences of gold coins and tungsten gold plated coins might be one method, though I myself don't know if a simple multilmeter set to the Ohm setting would be adequite to accurately measure resistance levels. |
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Lemon Thrower
1000+ Penny Miser Member
USA
1588 Posts |
Posted - 11/24/2009 : 07:05:21
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my understanding is that tungsten has a similar density to gold, but a much higher melting point.
the counterfeiters chop up the tungsten and place it inside the gold. so the outside is gold, bits of the inside are tungsten. so a hardness test is not helpful, and a ring test semi helpful.
i'm reminded of a crook on the show beating vegas. he was an engraver and spent over a year engraving a die to make a fake casino token. his was better than the original. he plopped it in and nothing happened. he researched the machines and found out that they have something like a discriminator that sends an electric pulse through each coin and reads its electronic signature. he was using a different alloy and so to the eye they were the same electronically they were different. he ended up having to order some very exotic alloys to stamp the coins, and that is how he got caught. |
Buying:
Peace/Morgan G+ at $15.00
copper cents at 1.3X
wheat pennies at 3X
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