No more 90% coins from the US Mint

Discussion in 'Coin Chat' started by Collecting Nut, Feb 20, 2019.

  1. Collecting Nut

    Collecting Nut Borderline Hoarder

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  3. Dougmeister

    Dougmeister The Coin Scavenger © ¯\_(ツ)_/¯

    Yeah, I remember hearing this somewhere. Aren't the Apollo 11 commemoratives all 99.9% Ag?
  4. -jeffB

    -jeffB Greshams LEO Supporter

    That's a very interesting article. Thanks for the link!

    I have to admit that I have mixed emotions about the shift. It bugs me that new silver issues won't be the same composition as traditional issues, but I do see the benefits.
  5. paddyman98

    paddyman98 No Common Cents! Supporter

    What!? I thought current silver minted coins were all pure silver! :wacky:
  6. NSP

    NSP Well-Known Member

    Thanks for sharing the article. I found the copper/silver solubility issue to be particularly interesting, so I looked up a phase diagram.


    It’s been a while since I’ve tried to read one of these things, but it appears that if you’re trying to make a silver/copper alloy that’s mostly silver (and only have one phase), you’d want to make the β phase (on the right). It looks like the most copper that can be dissolved in silver is 8.8% (100% - 91.2%), and even that would be at 779 °C. Copper is even less soluble as the temperature drops. If too much copper is added, you move into the region where two phases are present: α + β. This would be consistent with what the mint reported.
  7. hcmusicguy

    hcmusicguy Member

    I do prefer the jingle of the .900 alloy over the .999 coins, and tend to be a traditionalist when it comes to coinage, but I definitely understand the benefits of moving to .999. Hasn't Canada already been doing their numismatic non-bullion issues like this for years now?
  8. TheFinn

    TheFinn Well-Known Member

    Canada has been doing .925, Sterling. They did some in .500 when the price of silver got high, but collectors told them they would prefer the higher percentage, even with the higher prices.
    LakeEffect likes this.
  9. calcol

    calcol Supporter! Supporter

    Well, they could make coins 8% copper, 90% silver and 2% depleted uranium. They'd jingle nicely and have some heft. Might want to think twice about putting them in your pants pocket though. o_O

    micbraun likes this.
  10. -jeffB

    -jeffB Greshams LEO Supporter

    You're on the right track. ;)
    calcol likes this.
  11. RonSanderson

    RonSanderson Supporter! Supporter

    Did anyone else notice that the article explains milk spots and haze in passing? The copper exceeds the amount that can dissolve in silver and causes haze and spotting.

    This has been presented as an inscrutable mystery in many discussions here on CoinTalk.
    Randy Abercrombie likes this.
  12. CoinCorgi

    CoinCorgi Derp, derp, derp!

    I noticed, but this "theory" is disputed in the comments. Like you said, they alluded to it in passing but provided no discussion or definitive evidence. One of the comments mentions that milk spots show up on coins that are 99.9% silver. So that leaves us...?
  13. green18

    green18 Sweet on Commemorative Coins Supporter

    Exactamundo..........the mystery persists.
  14. RonSanderson

    RonSanderson Supporter! Supporter

    Ah, yes. I didn’t notice the comments section.

    And even at .999 there was still a 10% rejection rate due to haze.

  15. Razz

    Razz Critical Thinker

    It's all NCLT anyway made for collectors and not to be handled or spent...
  16. CoinCorgi

    CoinCorgi Derp, derp, derp!

  17. Razz

    Razz Critical Thinker

    Busted me! I have no idea really:rolleyes: I think it means non circulating legal tender. Basically modern silver coins minted for collectors...what does it matter really if they are 99% or 90% silver? Especially non proof coins.
  18. fretboard

    fretboard Defender of Old Coinage!

    Apparently it matters a lot to some collectors. ;) Especially since the prices on the 90% 2018 Kennedy Half Dollar reverse proof are going through the roof! Us talking here may make it even more pricey, who knows? :D
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