Cause of Red Spots on Gold Coins

Discussion in 'Bullion Investing' started by desertgem, Aug 26, 2010.

  1. desertgem

    desertgem MODERATOR Senior Errer Collecktor Moderator

    Red stains on Gold Coins have been often discussed on CT, but I ran upon this article which has scientific results on a Gold Panda Coin. Thought you might be interested. I highlighted in red, the pertinent results, IMO.

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    GDJMSP Numismatist Moderator

    Don't you find it interesting that they say they detect silver and sulphur on the untoned part of the coin - and that being a .999 gold coin.
    midas1 likes this.
  4. Hobo

    Hobo Squirrel Hater

    Copper spots are common on 90% gold coins because the coins are 10% copper.
  5. BadThad

    BadThad Calibrated for Lincolns

    If anyone has a gold coin with such spots, I would enjoy testing it using our electron microscope with EDXRF. :)
  6. medoraman

    medoraman Supporter! Supporter

    I thought the other 10% was frequently copper and silver, not just copper.

    I have always heard that the metal preparation on Pandas was not great. If they weren't so cute I would think they would sell at a discount.
  7. desertgem

    desertgem MODERATOR Senior Errer Collecktor Moderator

    Yes. but they didn't say how much. I would have been interested if it was more than .1 %, since gold doesn't actually combine with the silver atoms, it is more a mix than anything else, and either atom could move in relationship to the other under heat or pressure.

    The relationship of holes in the target area of tarnish was interesting also to me, as it indicated the striking pressure/flow lines might change the location points of silver compared to gold atoms. But the "red spot" if it is a silver tarnish should react to silver dips, but several have said it doesn't help?


    GDJMSP Numismatist Moderator

    Copper spots appear on all gold coins from time, even the .9999 gold Buffalos sold by the US Mint. It's not something that only happens to Chinese coins. And it is not something new either, it has occured since the first coins.

    Science says that gold can't tone. Observation of reality says that it can.

    GDJMSP Numismatist Moderator

    I truly hope that you can come up with a scientific answer some day Jim, but nobody else ever has and they obviously have not stopped trying. As I've said before - I don't know why gold tones. And I really don't care. All I know is that it does. And that's enough for me.
  10. krispy

    krispy krispy

    Unfortunately it is very true that AGBs develop red spots and quickly too.

    Below is my Proof 2006 AGB in OGP, which I have never removed from the Mint capsule and keep stored in a dry, humidity regulated space. I do still own this example but have been wanting to sell it when gold goes hyperbolic (!) and NO you guys cannot test it with your golden gun laser scanners! The spot is on the rim near 10 o'clock. I will not remove the coin from the holder for better pics so this will have to do. I can't point to them here but with high magnification there appears to be other spots developing. I bought this straight from the Mint.


    Compare that to these two 1989 Panda gold coins, which I bought new from a coin dealer in 1989 and have just recently sold earlier this year so I no longer own these two. The spots did not deter interest in buyers (IMO) even selling a bit over spot price.:

    1/10th oz. developed spots on one side only.

    1/2 oz developed spots on both sides.


    Note that both Panda coins were left in their sealed plastic wrap that they came in for over ten years prior to going into Air-Tite Holders.
  11. medoraman

    medoraman Supporter! Supporter

    I agree they can be on any gold coin, and have seen them on all, but it just appears to me, and maybe just me, more frequent on the Pandas. When I asked around, I heard the same. Not scientific or anything.
  12. GDJMSP

    GDJMSP Numismatist Moderator

    And here's two coins both minted almost 500 years ago and of pure gold. Notice the difference in color - one has been dipped and the other has not.

    And don't try and tell me it's the pictures either. I took the pictures, one right after the other. Same camera, same exact settings, same exact lighting, same exact angles, same exact everything.

    Gold tones, even pure gold. And it always has.

    Attached Files:

  13. medoraman

    medoraman Supporter! Supporter

    I agree that gold "darkens", that is the best description I can think of. I have tried searching, anyone ever hear of analysis of the toned surfaces of gold? I would be curious if it was an oxide or sulfide or what. That would help in preservation I would imagine. All of the sites I looked at said gold toning is due to impurities in the metal, specifically silver or copper.
  14. elaine 1970

    elaine 1970 material girl

  15. krispy

    krispy krispy


    Here you go Elaine!

  16. desertgem

    desertgem MODERATOR Senior Errer Collecktor Moderator

    I also believe that gold coins tone, but I still must say there is no scientific evidence for pure gold ( 100% or at least 99.999%) to tone under any conditions on the surface of the earth. I keep looking for some evidence, but all really seem to point at a reaction with the trace elements other than gold :) Just me and IMO.
  17. Cloudsweeper99

    Cloudsweeper99 Treasure Hunter

    I would think it is possible that even if a coin is .999 pure, the environment around it near the end if the process could be slightly contaminated with something that touches the surface and causes the stain.
  18. GDJMSP

    GDJMSP Numismatist Moderator

    You know why I think they say that ? Because they don't have any other explanation that they are willing to accept. They know it tones, the evidence is undeniable. But they can't explain why it tones because they believe it should not. Well, as happens with so many things, personal beliefs tend to blind people to the truth that is right in front of their eyes and they simply can't see it.

    Truth requires complete objectivity and always keeping an open mind. And that is a lot harder to do than it is to say.

    Regarding the accuracy of the explanation that it is impurities that tone and not the gold itself - ask yourself, does that really make sense ? Take the two coins I posted pictures of, does it makes sense that 0.001% impurities is enough to cause the entire surface of that coin to tone ? It sure doesn't to me.

    So about the only acceptable explanation is that gold does tone.
  19. spock1k

    spock1k King of Hearts


    Please think about this. Pure gold does not tone. Period. GD has this strange notions about pure gold. there were no pure gold coins till very recently 99.99 the other impurities in the coin tone anything I tell him wont make him see that so i dont anymore but if you start saying gold coins tone then we are in for a rough ride.

    There is a difference between a gold coin pure gold and a pure gold coin. Pure gold and pure gold coins dont tone. Have you had a first spouse coin tone? that should be a starting point
  20. spock1k

    spock1k King of Hearts

    grandpa that is not a pure gold coin it has generous doses of impurity mixed in it. :D
  21. spock1k

    spock1k King of Hearts

    yes with the other 0.001 but who will acknowledge that. i keep harping on it. even salt water doenst have an effect on pure gold
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