Do gold coins tone?
 

I have noticed that on my Gold maple leafs and k-rands some places are darker than others, but not on my gold eagles. Any reason for this?

Re: Do gold coins tone?
 

On some of the older US Liberties which are an alloyed with copper coin, I have seen concentrations of copper that give a spotted or blotchy effect and after many years in peoples pockets most turn an almost khaki colour. That may be the Krugerand problem copper spotting and or general handling.

As for the Maple that is supposed to be.999 percent pure, so copper concentrations are quite out of the realm of possibility. Is most likely handling related and cleaning should only be attempted after some research into the subject. Whatever you do don't attempt to polish either of them.

Re: Do gold coins tone?
 

Thanks Strudly.

Re: Do gold coins tone?
 

Some 999 gold coins have tiny brown spots on the surface, especially visible on proof coins. In a 999 gold alloy, the remainder is usually silver. This, upon solidification of the alloy, tends to separate out in small crystals or droplets. Where these contact the surface of the coin, they will tarnish, the tarnish layer being very thin and creeping out of the crystal over the coin surface. When you look at it with a scope it is rather a mixture of rainbow colors but with a bare eye it appears as reddish brown. Sometimes the spot has a very dark, almost black central part, which is the silver crystal itself, surrounded by a light brown circular area of tarnish.
If you have this problem on a proof coin I'd suggest you rather do not attempt to remove it. It is in fact a good proof of its purity, and the coin is easily scratched and all... If you really must remove the spots, a dip in 65% nitric acid (chloride free!) for a minute or so will do the job. This will etch the silver away, the spots will now be a gold color but will appear "matted" on a polished proof surface. After the acid dip, wash the coin in distilled water.
If you do this with proof coins - you may have trouble finding distilled water (or any solvent) pure enough to not leave any visible residue on the surface. The only thing that worked for me was 99,9% methylene chloride. Also make sure that any tools used for handling the coins do not even slightly dissolve in any of the solvents you use. :albertein
There exists a similar problem in some Sovereigns, which have copper showing up on the surface as red spots (maybe related to what Sturdly described). This can be removed in the same way.

Re: Do gold coins tone?
 

I have a related question. I ran across a dealer in Coin World, KJP & Assoc. Inc., He has some pre 1933 U.S. $20 Gold Coins that are MS/BU Grade but have been cleaned. ANACS would send them back in a body bag from what I understand. Therefore the aren't really MS/BU. However, he is offering them at $40 over spot. APMEX has similar $20 pieces, EF-AU+ at $50 over spot. Gold Eagles are $25 over spot at APMEX. I would like to find some common pre-33 coins that don't demand high premiums.
1. Is there any advantage to buying Pre-1933 US that can't be graded (been cleaned) but in excellent condition this close to spot. 2. Has anyone delt with KJP before and what was you experience with them? 3. Does cleaning virtually wipe out numismatic value? Feedback, Info, Thoughts & Opinions Appreciated.