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 Replies: 34 / Views: 2,840 |
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Valued Member
 United States
127 Posts |
I have a very strong magnet, it didn't stick at all.
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Moderator
 Australia
16847 Posts |
Quote:
I have a very strong magnet, it didn't stick at all. That's good, and that rules out a plated-steel fake - but for testing silver with a magnet, you're not looking for "sticking to the magnet", in the sense of the way a piece of iron or steel sticks to a magnet. You're looking for eddy current generation. You've already got a strong magnet, that's all you need for the test. Get another coin of about the same size as your piastre, that you already know for sure is good silver - a Morgan/Peace dollar or something like that. If the coin is in a stapled 2x2, you'll need to take it out, because staples will interfere with this test. Put the coin down on a flat smooth surface, and quickly wave the magnet back and forth above it in a swiping motion (without actually letting the magnet touch the coin). You will notice the coin seems to "grip" onto the magnet and want to move with it, but is only attracted to the magnet while the magnet is in motion - the faster the motion, the stronger this mysterious grip seems to be. That's the eddy current effect, and silver generates eddy currents better than any other metal because silver is the best electrical conductor of any metallic element. Now place your piastre down on the same surface, and repeat the magnet swiping technique. This coin ought to be about the same weight and fineness as a US silver dollar, so should behave exactly the same, if it is indeed made of silver. If it's made of pretty much any other alloy that looks like silver but contains no silver, you won't see the same eddy current effect - it will barely move under the magnet, if at all. Don't say "infinitely" when you mean "very"; otherwise, you'll have no word left when you want to talk about something really infinite. - C. S. Lewis
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Pillar of the Community
United States
1915 Posts |
Sticking has nothing to do with it.
Suspend the magnet and approach it with the coin.
It should repel as an initial good sign.
The magnet will push away from the coin if good silver.
But it is not foolproof.
The only positive certain reaction is no reaction at all indicating no elemental silver.
Others will argue a similar proper reaction may be with copper.
They are not wrong.
That is why SG can be very helpful: to sort out similar results from different metals.
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Valued Member
United States
127 Posts |
I guess the magnet I have isn't as strong as I thought (although it really grabs anything metal). I used a 1921 Morgan (my others are NGC slabbed and I don't want to break them open). I didn't notice any type of gripping action, but I did feel a very slight tug with the Morgan that I did not feel with the Piastre. Now here's the interesting thing that I did notice....the Morgan is actually slightly heavier at 26.73 gr versus the Piastre at 26gr (and yes I realize the Piastre should weigh more). Both coins are reputedly Silver .9, the Piastre should be ASW: 0.7813oz and the Morgan Silver 0.7734 oz. The Piastre is 3mm and thicker with the expected 39mm diameter versus the Morgan 38.1, and my rough guess is the Morgan is thinner at about 2.5mm. So, they're both .9 silver, the Morgan weights heavier, yet both the diameter and thickness of the Morgan is less?
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Valued Member
United States
127 Posts |
Ah hah, OK Albert, I went back and opened my safe and got the Morgan out again. I tied my magnet to a piece of sewing thread and suspended it. Approaching the magnet from the face of both coins seemed to do nothing....then I tried the rim. The Morgan caused the magnet to sway slightly away, but the Piastre definitely drew the magnet towards the coin. I've tried this several times with the same result. Would that maybe be indicating something like a cupro-nickel planchet?
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Moderator
Australia
16847 Posts |
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...I did feel a very slight tug with the Morgan that I did not feel with the Piastre...
...The Morgan caused the magnet to sway slightly away, but the Piastre definitely drew the magnet towards the coin...I would say that that's conclusive proof that it's not silver - whatever it is. "Nickel silver" (more correctly a nickel-brass with zero actual silver content) is most likely. Don't say "infinitely" when you mean "very"; otherwise, you'll have no word left when you want to talk about something really infinite. - C. S. Lewis
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Pillar of the Community
United States
1915 Posts |
Generally a typical copper-nickel coin has no or next to no attraction but does not react like good silver.
N-52 magnets are easily found online and come in suitable sizes for coin testing.
Round like 1/2 inch or more can be combined pinched on a thread to form a pair, or four suspended magnets.
I use a standard first test suspended pair of only a quarter inch diameter.
Experiment with a known good silver coin in what you do.
Compare the topic coin in the same way.
Larger silver coins give better results, especially with a home SG test.
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Valued Member
United States
127 Posts |
Albert's test intrigued me, so I pulled 3 other Piastres from inventory and tested with this magnet-on-a-string. One I was pretty darn sure is authentic...a 1909A and another I was suspicious of due to a weight variance of 26.5 gr....a 1908A. Then the 3rd is a fake 1895A (which I've posted before). The fake neither attracts or repels the magnet from the coin rim. Sadly, the rim of the 1908A pulls the magnet to the coin. Ouch. This was one I was always on the fence about.
Valuable lesson learned. Albert, I think you're on to something here, but the only thing I would add is to test the coin from the rim and not the face. It seems there is a better chance of detecting a problem that way.
Now I get to mark my 1908A as a suspected copy. Wish I had learned this test sooner.
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Valued Member
United States
127 Posts |
Albert, This is going to seem like a dumb question, but does it matter if a round countersunk magnet comes as a north pole or south pole? In other words, I want to buy these so that there is a hole in the middle so I can tie to it and suspend it. And I'm assuming 12 or 15mm would be a good size, as that seems to be the closest to matching the 1/2" you talked about.
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Pillar of the Community
Canada
5246 Posts |
@Paul St. Louis, every magnet has both a north and south pole.
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Valued Member
United States
127 Posts |
I didn't know why they were trying to make that distinction on ebay, so I figured I would ask instead of wonder...in case it mattered at all. The listing that prompted the question is worded as ..... Rings Countersunk N52 Super Strong Rare Earth Neodymium Magnet North South Poles, and then you can select from there a 'n' or a 's' pole. What I know about magnets you could fit on the head of a pin. Grin. |
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Pillar of the Community
United States
1915 Posts |
Amazon or K&J Magnetics. N-52 Look for a plain disc in several diameters and thicknesses up to a 1/4 thick more or less. Pinch them between a string, thread, tape or rubber band so they are free to swing. Approach the magnets by face and compare how known silver and known non-silver make the magnets react. Try silver, brass, copper-nickel, good silver and more. Watch and see how the suspended magnets react. Reverse the same and suspend the coin. Approach with a magnet and see how the coin reacts. You should see how silver acts one way compared to non-silver.
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Moderator
Australia
16847 Posts |
Magnetic monopoles (magnets which have north-only or south-only) don't exist - they're not barred by the theoretical laws of physics, but every physical magnet ever made has both, and no-one has any idea what a monopole might actually be made of. If you take a traditional horseshoe magnet (where one prong is north, the other south) and break it in half, new magnetic poles form at the break, so each half of the magnet still has a north and south.
You might be able to make a magnet in such a way that one pole is concentrated in a small area and the other pole is spread out and diffused, which is probably what they're talking about. A ring magnet might have the north around the inner face of the ring, and the south on the outer circumference, for example. In which case, the answer to your question is "no" - it doesn't matter which one you use.
If you're going around buying a bunch of powerful magnets, you might want to consider making yourself a "coin slide" - just look up "silver tester coin slide" on Google or YouTube, for ideas on how they work and how to make one. Once you've made it, it's a lot simpler to set up and use than fiddly pieces of string, especially outdoors where wind might interfere with your observations - and you can even carry it with you to the outdoor markets, coin shows, and such places where you might be offered silver of dubious authenticity.
A final word of warning: those supermagnets are powerful things. Don't let an actual iron or steel object touch them or even go near them, and don't let two of them touch pole-to-pole, or you might never pull them apart again. I brought a supermagnet testing rig to a coin club meeting once, and a visitor to the club happened to bring along a bunch of coins he'd bought in the street markets in Vietnam. He asked me to test his coins, so I started to put one near my magnet, and BANG - darn thing stuck to the magnet so fast it nearly took off my fingers. So yeah, those ones were plated-steel fakes. So if there's a chance that a coin in your hand might be a steel fake, check it with a weak magnet first.
Don't say "infinitely" when you mean "very"; otherwise, you'll have no word left when you want to talk about something really infinite. - C. S. Lewis
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Pillar of the Community
United States
1915 Posts |
I experimented with magnet slides and they have their usefulness for me because I collect and detect fakes.
May not be practical for someone with only one or two dubious coins.
I tried six designs and settled for two that work the best.
Depending on the size and power of the magnets some unexpected results can appear.
Aluminum comes to mind.
And yes they can pinch making for bleeding fingers.
They can slam together and fracture easily.
I have a magnet separator made for that purpose from K&J Magnetics.
With some coins it can be curious as to what to make of the reactions.
Your own magnet slide can be too weak or too strong for the best results.
I posted pictures of some examples a couple years ago.
Edited by Albert
09/08/2023 02:19 am
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Pillar of the Community
United States
1915 Posts |
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Replies: 34 / Views: 2,840 |
First Page
Posted 09/07/2023 5:39 pm
