"Copper spots" on gold coins and bars

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rickbb

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So, I've seen this on other forums about collecting gold coins and bars, "stacking" as they call it. Most of the people there seem to think that newly minted .999 gold can develop spots, they call them copper spots.

They claim that this is normal and caused by the metals not being mixed well and to just take a butane torch to burn them out.

Am I crazy to think that pure 24K, .999 gold should not have any kind of spots, copper or otherwise. And even if it's an alloy with copper that "mixing" so badly that the spots show is not a good or normal thing?

I've voiced my opinion that this is not normal that pure gold should be just that, pure. They think I'm being silly.

Seriously is this a thing.

Edit to correct spelling.
 
rickbb said:
So, I've seen this on other forums about collecting gold coins and bars, "stacking" as they call it. Most of the people there seem to think that newly minted .999 gold can develop spots, they call them copper spots.

They claim that this is normal and caused by the metals not being mixed well and to just take a butane torch to burn them out.

Am I crazy to think that pure 24K, .999 gold should not have any kind of spots, copper or otherwise. And even if it's an alloy with copper that "mixing" so badly that the spots show is not a good or normal thing?

I've voiced my opinion that this is not normal that pure gold should be just that, pure. They think I'm being silly.

Seriously is this a thing.

Edit to correct spelling.
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Seems strange to me.

There is not enough foreign metal to even be visible if it is 999.
It may be possible that if there are loose metal dust the it some how stains the surface, not sure if it is possible though.
A quick Nitric wash will fix this, if it is even a thing though.
 
At least with silver it is known as "toning". The silver will take on a metallic sheen that varies in color and some collectors even look for this for its uniqueness.
 
Spotting is extremely rare on .995 and even .990, but can be seen on .900, depending on the storage environment.

The causes, on pure gold (.999 through .9999) are all external, as far as I know. Typically moisture, over time, can contaminate the surface of gold coins and bars with impurities from local atmosphere. That is why I store both .999 gold and .999 silver in a sealed container with both oxygen and humidity adsorption.

No, moisture from atmosphere is not pure water.

The most common way that .999 gold gets spotted while in storage is when there is physical contact with other metals. It does not matter much what the other metal is, either. Oxidation, coupled with other effects that I simply do not remember from high school chemistry, will cause the surface other metal to pass any effects to the surface of the gold coin or bar. Generally, the less humid the storage area and less reactive the touching metal is, the less likely any staining is. When is does happen, it sometimes takes years for the effect to be visible.

Time for more coffee.
 
goldshark said:
I am wondering if slightly different alloys (less than .900 fine), might induce a galvanic reaction.
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They do. Typically, the metals must be touching one another. Very similar to the reaction I mentioned above. Which metals this occurs with? I do not recall from that many decades ago.

Time for more coffee.
 
galenrog said:
Spotting is extremely rare on .995 and even .990, but can be seen on .900, depending on the storage environment.

The causes, on pure gold (.999 through .9999) are all external, as far as I know. Typically moisture, over time, can contaminate the surface of gold coins and bars with impurities from local atmosphere. That is why I store both .999 gold and .999 silver in a sealed container with both oxygen and humidity adsorption.

No, moisture from atmosphere is not pure water.

The most common way that .999 gold gets spotted while in storage is when there is physical contact with other metals. It does not matter much what the other metal is, either. Oxidation, coupled with other effects that I simply do not remember from high school chemistry, will cause the surface other metal to pass any effects to the surface of the gold coin or bar. Generally, the less humid the storage area and less reactive the touching metal is, the less likely any staining is. When is does happen, it sometimes takes years for the effect to be visible.

Time for more coffee.
Click to expand...
Thanks, just what I was looking for. So now I have to go back and tell them I was being silly but not for the reason they thought.
 
a few years ago, i had some silver rounds that i ordered from a distributor and they showed up failing the metalytics tester that i use to test my bullion. big time. i called to report my findings and my displeasure, and the lady told me that they test all of their material. i told her i was going to post a video of my testing, and asked her to pass the video along to the powers that be. while making the video, i ensured that the distributor's name was not noted, but gave them plenty of evidence that the rounds they were shipping were NOT .999 fine, as marked by the refiner. they were more than eager to make things right, so i sent them back and instead ordered some of their random 1oz gold rounds. they were nice enough to send me .99999 fine canadian rounds in assay at the price of their random gold rounds. a win-win.
 
Master Nater said:
a few years ago, i had some silver rounds that i ordered from a distributor and they showed up failing the metalytics tester that i use to test my bullion. big time. i called to report my findings and my displeasure, and the lady told me that they test all of their material. i told her i was going to post a video of my testing, and asked her to pass the video along to the powers that be. while making the video, i ensured that the distributor's name was not noted, but gave them plenty of evidence that the rounds they were shipping were NOT .999 fine, as marked by the refiner. they were more than eager to make things right, so i sent them back and instead ordered some of their random 1oz gold rounds. they were nice enough to send me .99999 fine canadian rounds in assay at the price of their random gold rounds. a win-win.
Click to expand...
It's why I like sreetips so much. He shows absolutely every part of his processing to guarantee the resulting purity.
 

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