Red spots on .9999 pure gold coins?

I have discovered red spots on two .9999 pure gold bullion coins. One is a 2006 Buffalo Proof directly from the US Mint. The other was a 1989 $50 Maple Leaf. Since .9999 gold coins are not supposed to get red spots, I'm wondering what these could be? Both coins were stored carefully, and both were checked with a digital scale and micrometer to insure that they are not counterfeit.

Any ideas. And standard coin cleaners (MS70 and E-Z-est) have no effect.

 

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I have a gold bar (1 gram) from pamp suisse. It is pure gold (9999 fine), it has more of a black/reddish spot on it. I was wondering the same thing and made a thread on it a couple years ago. What's possible is what happens is there was something on the bar/coin after it was struck, which oxidized after it was minted, causing the reddish/color.

 

Welcome to CoinTalk.

Even though it is said that pure gold will not tone or become discolored, in practice it seems to happen fairly frequently. It sounds like your coins were exposed to something that got on the surface to cause the spots.

 

The dark red spots on my Buffalo (.9999 gold) look almost like little droplets of liquid that then dried on the surface. My theory is that it was some kind of lubricant or coating used in the press machinery that splattered onto the coins and then dried rapidly because the coins are hot right after they're pressed. It is impossible to get off with normal coin cleaning solvents sold by the hobby supply stores. I am reluctant to use anything stronger like an acid, because it will damage the coin. I'm going to give it one last try using Acetone. If that doesn't work, then the coin is still worth 1 oz of .9999 bullion.

 

I think trying clean it is a mistake. Sell it and buy another that you like.

 

I agree. It seems like these red spots are somewhat common on Gold Buffalos. If you don't like it, you are much better off selling the coin you have and buying another without the spot.

 

Thanks for the advice everyone. I appreciate it. I'll probably just sell it with the spots.

 

Join the crowd!! The attached image is of a 2006 PCGS MS69 $50 FIRST STRIKE, which has hideous red discoloration (over a large area) and nicks (darker spots in discolored area above left front leg) on the reverse image. Although less obvious in this photo, it is very recognizable when "sight seen". It is one of several I received in this condition, all having same date/grade. It provided new appreciation for "MS69 full mint luster and brilliance" as defined by a "top tier" TPG. I hope the Grade/Certification allows full recovery of the purchase price, as I'm certain we both, nor others, expect this condition on a "high grade" 24 Kt. Gold coin. I would also appreciate an explanation for this condition.

 

Great enlightening post!!

We're of similar knowledge base on this subject, but as a scientist I still crave a plausible explanation for this unexplained "rust" occurrence, throughout the centuries, on a touted "noble" metal. Once realized, I'll then continue to pursue the a greater than hocus-pocus origin of universe explanation.

 

I've always thought they were copper spots, but then again I'm not much of a gold guy.

 

Well, if the gold is not 100%, it must be alloyed with something. I guess I always assumed it was copper, because all the gold coins up until 1933 were alloyed with copper or a mixture of copper and silver.

If the coin is only .999, or even .9999 fine, then there must be either 1/1000 or 1/10000 part, respectively, that is something other than gold. Why not copper? I would argue that even 1/10000 part of copper in a coin is enough to make it spot.

 

Ahh, back to advanced science!

The colors we see for gold and copper are not simple to explain as just % of the metals. They only have their color on the surface and in energetic light ( photons source). When gold is added to glass, the color is red ( "Ruby glass"). I would agree with Doug that the red color does obviously exist on some gold coins, but I believe that gold is still a noble metal and is uncombined with any other metallic atom in the coin. Reflections from electron cloud surface tends to produce the reflective addition and can only be separated by using gold so thin it is transparent to a degree. Then the color ( since it is too thin for an electron cloud reflection) tends to be blue green.

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http://books.google.com/books?id=-f...v=onepage&q=gold color quantum theory&f=false

Since the color of gold depends so much on the energy of photons striking the surface, it might be feasible ( speculation) that some chemical material during processing might become annealed to the surface and due to its chemistry block some photons of a certain energy level and thus produce the red effect (/speculation).

This is an interesting area, but research on some of the papers on color of metals and quantum effects can clear some of the thoughts. IMO.

Jim

 

An Interesting Hypothesis!

Your advanced possible explanation is somewhat reasonable, but still not plausible, or yet an axiom, a hypothesis without complete basis. I'll still anticipate an explanation of what conditions/chemistry generates the RED random deposits on GOLD surfaces. I believe it is a chemical bond, as I've gone through numerous experiments to neutralize same, and had limited success.

 

I'm wondering why you guys call Gold a noble metal.....Nobel as in a nobel gas. Nobel gases don't combine with anything, they just are. Gold can be made into an alloy, so I'd think a chemical bond with something else is possible. If a chemical bond is possible, then if a metal is 100% pure, this might leave bonds that haven't combined with anything. I wonder if something, possibly oxygen, chemically combines with the metal at the surface. I wonder because I remember an experiment in college where we tried to explain the refractive index of a purely silicon substrate. It turned out to be that silicon forms 4 chemical bonds, so if the substrate were 100% pure silicon, there would have to exist "dangling" bonds, just waiting to combine with something. That something turned out to be oxygen, and the refractive index proved that sure enough, the surface of the substrate was actually silicon oxide.

 

Silversurfer, you can find several definitions on different sites. This one is from Wikipedia.

Gold for instance can form halide compounds such as gold chlorides, from use of aqua regia or from direct halogenation at high temperatures. They can also react with potassium cyanide to form a soluble gold compound ( used in gold mining), but such reactions are few and not normally ( probably never) applicable to the environmental conditions of gold coins.

Most sources consider alloys to be solid solutions and not chemically ( reacted) combined.

I would be interested in any chemical reaction of gold shown to occur under normal storage environments and not involving washing with aqua regia or potassium cyanide. However cyanide dips for coins were very popular over 100 years ago.

IMO.

Jim

 

I just checked, and there is Hydrogen Cyanide in cigarette smoke. So, finding cyanide in the local environment might not be that difficult. Wondering if the owner of the spotted gold smokes, or has someone around who does?