DoChenRollingBearing
Yellow Jacket
One of my blog readers today sent me a link to a video (Portland, OR TV station) about fake Chinese gold and silver showing up here in the USA. I then asked three of my own blog readers (two scientists and one coin dealer) to advise me how to easily and quickly determine if a gold (or silver) coin is fake or not.
Much of the video concerned NUMISMATIC fakes though. Here's the link to the video:
http://www.shtfplan.com/precious-metals/chinese-counterfeiters-flood-global-markets-with-fake-silver-and-gold-100000-coins-from-a-single-counterfeiter_11102011
I got the below responses:
1) Thomas is a scientist:
Hi Robert,
The simplest way to test silver is to listen to the acoustic properties. Take a coin and flip it. It will have a nice ring to it. Lead alloys have a dull thump to them. Try flipping a silver quarter, then flip a new quarter. The difference is pretty striking, and it can't be faked by any method I know of.
For gold, the best way is to test the density by measuring the weight and the volume. Of course, there are now tungsten fakes supposedly floating around. Sonic testing would probably work here as well, though I have never tried it myself. It is my understanding that this is the way they test gold bars these days. (they use a computer, though). But you should be able to hear the difference pretty easily.
-Thomas
2) Doug is a scientist:
Sure, Bob, I like talking to smart people no matter how met. You can
pass on my info if you like.
Re the counterfeit. The old acid test, mentioned in the vid helps with
the surface of course, and isn't too hard to do. But I'd assume that
since electroplating is pretty cheap and easy, the surface would pass
that test...still worth doing since it's so easy I suppose, and it would
only damage fakes anyway.
Weight alone is better than nothing, but of course you want to measure
volume too -Archimedes to the rescue! You can see how much water some
coins displace in a graduated cylinder for example, and make sure the
density is correct - that will detect lead cores etc.
Tungsten cores (since the density is close) are harder - but tungsten is
a heck of a lot harder than almost anything - a spring loaded center
punch or bend test should take care of that one pretty quick.
More subtle might be the alloying of some other metal, which in small
amounts wouldn't show up easy in the density test, but would show up in
the acid test if there was much of it (and it was a base metal). I'd
think you could see the color difference if any amount of say silver was
added to gold with the eyeball.
Else you're down to more destructive testing - melting point, scraping
with a knife to see below the surface and so forth. Ultrasound will
only work on fairly thick stuff, because the transit time in metal is
really fast.
And of course, here in my fusion lab, I could to radio-activation and
look at the resulting gamma spectrum....but since most activations make
mostly beta rays, and only incidental X rays, you'd primarily be testing
the surface metal, not the whole thing.
3) Lewis is a coin dealer (the fisch products are a clever fitted balances to check dimensions and weight of various PM coins):
http://www.fisch.co.za/orderonline.htm#pricing
http://www.fisch.co.za/operation.htm
http://www.onlygold.com/TutorialPages/Coin_specsFulScreenVersion.htm
http://about.ag/JohnsonMattheySilverBars.htm
http://www.coinweek.com/commentary/...le-bullion-cash-transactions-or-lack-thereof/
http://news.coinupdate.com/irs-and-...quirements-for-coin-and-bullion-dealers-0353/
See what you can use from the above links.
LEWIS
Much of the video concerned NUMISMATIC fakes though. Here's the link to the video:
http://www.shtfplan.com/precious-metals/chinese-counterfeiters-flood-global-markets-with-fake-silver-and-gold-100000-coins-from-a-single-counterfeiter_11102011
I got the below responses:
1) Thomas is a scientist:
Hi Robert,
The simplest way to test silver is to listen to the acoustic properties. Take a coin and flip it. It will have a nice ring to it. Lead alloys have a dull thump to them. Try flipping a silver quarter, then flip a new quarter. The difference is pretty striking, and it can't be faked by any method I know of.
For gold, the best way is to test the density by measuring the weight and the volume. Of course, there are now tungsten fakes supposedly floating around. Sonic testing would probably work here as well, though I have never tried it myself. It is my understanding that this is the way they test gold bars these days. (they use a computer, though). But you should be able to hear the difference pretty easily.
-Thomas
2) Doug is a scientist:
Sure, Bob, I like talking to smart people no matter how met. You can
pass on my info if you like.
Re the counterfeit. The old acid test, mentioned in the vid helps with
the surface of course, and isn't too hard to do. But I'd assume that
since electroplating is pretty cheap and easy, the surface would pass
that test...still worth doing since it's so easy I suppose, and it would
only damage fakes anyway.
Weight alone is better than nothing, but of course you want to measure
volume too -Archimedes to the rescue! You can see how much water some
coins displace in a graduated cylinder for example, and make sure the
density is correct - that will detect lead cores etc.
Tungsten cores (since the density is close) are harder - but tungsten is
a heck of a lot harder than almost anything - a spring loaded center
punch or bend test should take care of that one pretty quick.
More subtle might be the alloying of some other metal, which in small
amounts wouldn't show up easy in the density test, but would show up in
the acid test if there was much of it (and it was a base metal). I'd
think you could see the color difference if any amount of say silver was
added to gold with the eyeball.
Else you're down to more destructive testing - melting point, scraping
with a knife to see below the surface and so forth. Ultrasound will
only work on fairly thick stuff, because the transit time in metal is
really fast.
And of course, here in my fusion lab, I could to radio-activation and
look at the resulting gamma spectrum....but since most activations make
mostly beta rays, and only incidental X rays, you'd primarily be testing
the surface metal, not the whole thing.
3) Lewis is a coin dealer (the fisch products are a clever fitted balances to check dimensions and weight of various PM coins):
http://www.fisch.co.za/orderonline.htm#pricing
http://www.fisch.co.za/operation.htm
http://www.onlygold.com/TutorialPages/Coin_specsFulScreenVersion.htm
http://about.ag/JohnsonMattheySilverBars.htm
http://www.coinweek.com/commentary/...le-bullion-cash-transactions-or-lack-thereof/
http://news.coinupdate.com/irs-and-...quirements-for-coin-and-bullion-dealers-0353/
See what you can use from the above links.
LEWIS
