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Using a neodymium magnet to test silver coins - not conclusive?

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Miss Moneypenny
Joined: 13-Mar-2015
Posts: 121
So, I have watched the videos on YouTube (e.g., https://youtu.be/s78mPc4QhiM) and think it's pretty neat how you can use a small, powerful neodymium button magnet to test a silver coin (or medal) to see if it's actually made of silver.

Silver is diamagnetic (don't ask me to explain what that means, lol), so the magnet won't attract the coin directly, but it will slide slowly down the coin if held at an angle (e.g., 45 degrees) due to resistance. I bought myself a neodymium button magnet and it really does work, which is awesome. B)

However, I just discovered that copper (and apparently lead) is also diamagnetic! x.  Which makes me wonder whether a silver coin can be faked by silver-plating a copper/lead core, so that it possesses the look, feel and diamagnetic properties of silver, and possibly even the weight (with the right core content). Or would that be too much effort for fakers to bother with?

Kinda bummed, as the neodymium magnet test is easy to do and non-damaging, so I was hoping it would be conclusive. Haven't tried the ice test yet, as I don't keep any at home. Maybe I can scrape some build-up from my freezer, lol.
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BizzoDoes
Joined: 22-Jan-2014
Posts: 996
Quote: Miss MoneypennyHowever, I just discovered that copper (and apparently lead) is also diamagnetic! x.
Maybe your copper coin is fake?
Could be copper plated silver?  :°

I've never had one of those magnets, so can't really comment.
The only test that I've actually done is the ice one, and it is surprising how quickly a silver coin gets cold.
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I'm not an expert in any kind of coins, but I reckon I'm good at research and will do my best to help. Feel free to tell me my identifications/valuations/gradings are wrong. It's the only way I'll learn.
Miss Moneypenny
Joined: 13-Mar-2015
Posts: 121
Quote: BizzoDoesMaybe your copper coin is fake?
Could be copper plated silver?  :°

Haha, I hadn't thought of that. You could be right! :o ;)
Okay, off to the freezer to see if I have any frost/ice build-up... <:D

UPDATE
Well, I just had a look at my freezer, managed to chip off some frost build-up onto a plate, but by the time I got to my coin, it had all melted. x.  Lmao! Looks like I may need to conduct my coin testing in front of the freezer, or else invest in an ice cube tray. :~
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Miss Moneypenny
Joined: 13-Mar-2015
Posts: 121
Okay, so today I conducted my coin test whilst standing in front of the freezer, lol, and noticed the quick melting effect and cold transfer across a large silver coin.

However, for comparison purposes, I conducted the same test on a similar sized copper coin, and the melting/transfer effect was just as quick, if not more so!

Has anyone else noticed this? Maybe my copper coins are indeed fake copper-plated silver coins, lmao!
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ArnoV
Joined: 23-Nov-2011
Posts: 815
Silver is not attracted to a magnet, but not everything which is not attracted to a magnet is silver.

Iron and nickel (and some other metal which is not frequently used for coins) are attracted to a magnet. Steel is usually magnetic, but can be manufactured in such a way that it isn't (see WWII Italian and Albanian coins). I don't know if a threshold exists for alloys: how many percent of iron or nickel would make the alloy magnetic. At least copper-nickel coins are not attracted to ordinary magnets.

Cheap fakes of silver coins can be made of iron. If you doubt the authenticity of a silver coin, and it clings to a magnet, then it's a cheap fake.
If it doesn't cling, that doesn't prove that it's silver. Just that it is not iron, nickel or steel. But it can still be a fake. Or authentic.

Weight is an additional discriminating factor, as is the 'ice test'. If it's about serious money, ask an expert.
Miss Moneypenny
Joined: 13-Mar-2015
Posts: 121
In addition to measuring and weighing a silver coin and then comparing the data against the respective Numista catalogue entry, I usually conduct two quick magnet tests:

  • one to see if the magnet is directly attracted to the coin (this is to rule out iron, nickel and other ferromagnetic metals); and
  • the other to see whether there is any diamagnetic resistance when the coin is held at an angle, as seen in the YouTube link at top (supposedly to confirm silver content, except that copper and lead also exhibit this property!).

Presumably the ring test would easily rule out a silver-plated coin with a lead core, so the tricky one is copper. For me, at least, the ice test produces the same results in both! Copper also rings nicely, or maybe I'm too new/deaf to tell the difference. (Quite possible, lol.)

Weight (or density) is thus the only major difference, but what if the core is copper mixed with a little bit of lead to get the right balance? Thinking out loud mostly to myself, haha, but it's frustrating how there isn't one simple, non-damaging, definitive test!
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BizzoDoes
Joined: 22-Jan-2014
Posts: 996
Did you check out his follow-up video?
Real silver Panda vs. fake. Not hard to tell with a neodymium magnet!


Implying that the fake coins (and probably copper too) are still attracted to the magnet, but less so.
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I'm not an expert in any kind of coins, but I reckon I'm good at research and will do my best to help. Feel free to tell me my identifications/valuations/gradings are wrong. It's the only way I'll learn.
Miss Moneypenny
Joined: 13-Mar-2015
Posts: 121
Quote: BizzoDoesDid you check out his follow-up video?
Real silver Panda vs. fake. Not hard to tell with a neodymium magnet!


Implying that the fake coins (and probably copper too) are still attracted to the magnet, but less so.

Watched it just now. Yes, his example does show a noticeable difference, but my silver and copper coin both exhibit the same resistance. No major difference observed. Guess his fake silver coin doesn't have a copper core. Maybe I should do my own YouTube video, lol!
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BizzoDoes
Joined: 22-Jan-2014
Posts: 996
I don't know a great deal about Neodymium magnets, but maybe the test that guy's doing is with a different strength magnet? So the speed down the coin is noticeably different, maybe?

But one question I don't actually want to ask, how sure are you that your silver coin is silver?
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I'm not an expert in any kind of coins, but I reckon I'm good at research and will do my best to help. Feel free to tell me my identifications/valuations/gradings are wrong. It's the only way I'll learn.
Miss Moneypenny
Joined: 13-Mar-2015
Posts: 121
Quote: BizzoDoesI don't know a great deal about Neodymium magnets, but maybe the test that guy's doing is with a different strength magnet? So the speed down the coin is noticeably different, maybe?

But one question I don't actually want to ask, how sure are you that your silver coin is silver?
Hmmm, I'm not sure how strong my one is, but it is a bit smaller than the one he used in the panda coin video (like a button battery). However, I have two of them, and they're strong enough to attract each other through my hand or finger without coming apart! (Good fun to play with, btw. Might buy some more!)

As for my silver coin, that's a very good question! But I actually tried out my magnet on all of my silver coins and noticed the same. Guess the next question is whether all of my silver coins are fake!! :o  But I'd like to think that at least one or two are real, lol, especially since I bought them from various sellers!
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SolarPenny
Joined: 22-Feb-2012
Posts: 47
I just bought some of those magnets myself a few weeks back. Normally I trade for 1 oz silver bars so I have an electronic scale to measure the mass and then just use a fridge magnet to make sure they aren't magnetic. I did a bit of a bigger trade which got me a few 10 oz bars which is outside the range for my scale. I bought the magnets to conduct the slide test. I did not realize that lead and copper also possess a diamagnetic property, I will have to check and see if a notice a difference between some 1 oz copper rounds I have. Not sure about the lead though, I don't collect lead bars haha.
ZuluRaptorSpace
Joined: 3-Jun-2013
Posts: 1628
Quote: Miss MoneypennyPresumably the ring test would easily rule out a silver-plated coin with a lead core, so the tricky one is copper. For me, at least, the ice test produces the same results in both! Copper also rings nicely, or maybe I'm too new/deaf to tell the difference. (Quite possible, lol.)
Here's a tip:
Balance a coin on your hand, and gently tap it with another coin. Silver will "ring" in a very high-pitched (and beautiful) way, while copper-nickel will be similar, but less high-pitched. Never tried it on copper.
kolikko99
Joined: 6-Jun-2014
Posts: 1233
Quote: ZuluRaptorSpace
Quote: Miss MoneypennyPresumably the ring test would easily rule out a silver-plated coin with a lead core, so the tricky one is copper. For me, at least, the ice test produces the same results in both! Copper also rings nicely, or maybe I'm too new/deaf to tell the difference. (Quite possible, lol.)
Here's a tip:
Balance a coin on your hand, and gently tap it with another coin. Silver will "ring" in a very high-pitched (and beautiful) way, while copper-nickel will be similar, but less high-pitched. Never tried it on copper.
copper also has high pitched sound but the ring lasts shorter
Miss Moneypenny
Joined: 13-Mar-2015
Posts: 121
Won't the size and thickness of a coin affect the ring in terms of pitch and duration? Looks like I'll need to conduct a few tests!
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Miss Moneypenny
Joined: 13-Mar-2015
Posts: 121
Reposting here in case it's overlooked in the other thread...

Well, I basically pinged ALL of my coins the other night (luckily I still don't have very many!), and while I don't think I have the most discerning ear, two coins did stand out and I'd like to seek your thoughts.

Both potentially suspect coins seem to be of the correct size and weight (or within the acceptable range for a worn coin), and also passed my neodymium magnet test as described earlier. However:

  • One supposedly 0.833 silver coin from mid-18C Germany rings at a noticeably lower pitch (sustained, but low). Could this be related to what they used to alloy their silver coins with back then, or can coin age make a difference?
  • My Paul von Hindenburg 5 Mark coin, which is supposed to be 0.900 silver, rings very high in comparison to similar coins (e.g., the 0.900 silver Kennedy half dollar).

The ring/ping test is not foolproof, so I'm still keeping the two coins, but I'm curious to know whether this could indicate that they're *gulp* fakes and not silver. :snif:
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redsmithstudios
Joined: 20-Dec-2010
Posts: 2735
In the ice test, silver becomes instantly cold on the side opposit the ice, literally like within a second. Copper does not, it might be ice cold where the ice was, but it will not be ice cold where your fingers are. Try using a large piece of ice. Frost won't work.
Taking a break from swapping for a while, but still interested in pre 1799 Spanish coins, I will make time for that!

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Fluke
Joined: 22-Mar-2015
Posts: 1864
The "ping" test is flawed, it is density that controls the sound waves and will sound different if you use different types of metal to ping the coin, also taking into account you hit the coin with the rim or the face, the only way is to have one that is already certified as genuine and do a comparison sound but even that will be flawed, its the same principle with crystal.

I have used and known about neodymium magnets for some time (They are also referred to as "rare earth magnets" even though there is nothing rare about its contents or its plating.) They can range in various sizes, they can be dangerous as well the size of dice and larger, if you put one on each side of your hand then it will result in severe crushing of the hand, possibly breaking bones in the process. if that happens then you are in trouble because you wont be able to pull them apart.

They never lose magnetism and are the second most powerful magnet type next to high voltage electromagnets.

I use a 1cmx2cm stack of 2mm square 12 in total, works like a charm. I use it often if I get a job lot of mainly silver colour coinage to sort through, run it around the top of the pile and it will pull out all the magnetic coins effortlessly.

 Keep them well away from children goes without saying.
Restoration addict : Verdigris Removal : Zinc White spot removal : Iron Rust Removal : Silver brooch/necklace mount Removal
GSDykes
Joined: 12-Feb-2015
Posts: 8
The magnet test is not infallible. Certain copper nickel alloys can slow a magnet's downhill descent, and thus appear as "silver".  For example the big Medio-Balboa coins of Panama, 1973 -1993, (copper-nickel clad copper) appear to be silver with a rare earth magnet, they of course are not.   I would always do a specific gravity test to be certain!!  
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plenhardt
Joined: 3-Jan-2018
Posts: 12
Silver is diamagnetic. If the weight and diameter of coin are correct i use at next neodym magnet test.
With one light construction as my own (works same as magnetbalance) can you determine if the coin is silver. Suitable only for big(er) silver coins. From 0 to + values probably silver. - values =counterfeit
You need:
- precision Balance.
- two CD Boxes (25pcs).
- plastic ruler 20cm or thin wooden slat.
- magnet from one Harddisk.
- aluminium Profile (between Balance and magnet).
See pics (i cut the same construction from Ferrero rocher 200g box).

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