1927 $2.5: No I sold that years ago...it was MS64 though. Although I did have comments in the past that the quarter eagle had been subject to iodine but who knows? The only ones I still own are the Buffs. They look odd but I like them well enough...somewhat unique. jom
If the coloration is from gold iodide ( lugol's solution treatment) (AT) putting the coin in a hot distilled water bath for a period of time should greatly reduce or remove it.
I agree regarding the Saints for sure, and the color scheme is similar to that posted on my Saint above and about 6 or 7 other pieces I have seen. With the modern coins that you posted, it appears that the alloy was poorly mixed and a larger amount of copper than is normal accumulated near the surfaces and produced the toning phenomenon that you are referencing. In other words, I don't believe it is artificial.
It seems that some are intermingling the initial color when minted with the case of original color that has changed ( toning) over time. I will accept the first , but would argue the second, especially concerning the effects of copper, which tones by covalent chemical bonding with substances such as sulfur to produce a color change. Whereas, Gold and copper bond with metallic bonding ( sea of electrons concept), which is normally not part of elementary inorganic chemistry. I tried to find a reference that didn't involve quantum chemistry much and found this one http://www.webexhibits.org/causesofcolor/9.html Hopefully it will explain it. Yes, gold can have different coloration depending on the amount of silver or copper added to it, jewelry counters are filled with examples, but as long as gold is the majority metal, color change ( toning) should not occur naturally .
I don't disagree with your chemistry argument, but I do disagree with your conclusion that gold cannot tone naturally over time. Your argument appears to be predicated upon the flawed assumption that the alloy is always homogeneous, but we know that this is not always the case. After all, if it was, we wouldn't have copper spots on gold coins. And when impurities such as the trace metals and copper mentioned previously accumulate in larger amounts near the surface, it is absolutely reasonable to believe that toning could occur via natural mechanisms although admittedly it would be a scarce occurrence (as it appears to be). And of the Saints posted in this thread and that I have seen on other coins, the color pattern and progression is very similar. Edited: And I could have been clearer in my comments about trace metals and the color of gold. While gold takes on a characteristic color overall based on trace metals of some branch mint dated coins for instance, the thrust of my argument was that improper mixing of the alloy with these trace metals (and as always the approximately 10% copper composition for this and other pieces) could accumulate near the surfaces and facilitate toning. I am not conflating overall color of the alloy as struck and toning over time.
Thanks for the info! Coinchemistry: I saw your Saint as well and would have guessed it was a 1924 but you only showed the obverse.... jom
So these gold Buffaloes were poorly mixed alloy and excess copper caused the color? Yet they are .9999 ( 99.99%) gold. That is a lot of surface to cover with .0001 ( 0.01% ) non-gold atoms to produce such a depth of color.
Here is a beautiful $2 1/2 Indian with toning... not mine. They are asking too much in my opinion, but nice toning! http://www.ebay.com/itm/1911-2-50-N...60?pt=Coins_US_Individual&hash=item3a926a1284
If it is true toning on the piece, it is possible although it would be extremely rare, I won't deny it. The other possibility is that what we are seeing on that piece isn't toning but some sort of surface contaminant that has reacted. Maybe that is what the other poster was referring to with the surface deposits. My comments were meant more towards the pre-1933 range which is what I am more familiar with.
What I was referring to is simple smoke or other gases. Stored under certain circumstances any coin can develop a haze that if deposited on a lustrous surface will look like toning. Same as on a dirty window. I have cleaned items that looked like they were toned but were just smoke covered.
I misunderstood what you were originally stating (and I missed your very first post). With regarding to haze and organic debris, one would think that this would appear to sit on the surface rather than be a part of the surface as natural toning would. In reference to darker colors, however, you make an excellent point that perhaps some might confuse darkening with surface contaminants to be toning . Exposing gold coins to smoke is a trick that coin doctors have used in the past.
FWIW, every time a saint like the one I posted and you posted in this thread is shown, improper alloy mixing is always cited as the reason for the appearance and rarity of such toning.
I see this a lot in early silver a high grade coin that's untiuched and lusterless that's just filthy. A soak in acetone gets rid of this grime and the appearance is greatly improved!
Those who've been around long enough have heard of all the techniques to get gold to tone. Just putting it up on a shelf near burners will do something. Here is a heavily toned gold coin in an old holder, therefore whatever was done to it happened before grading: http://www.coinraritiesonline.com/index.php?page=archive&task=det_archive&offset=130&gal_id=1 Lots of different hues in their archive: http://www.coinraritiesonline.com/index.php?page=archive
http://www.ebay.com/itm/1836-Block-...5sbLxlnyNssFZRwisTnpk%3D&orig_cvip=true&rt=ncThis is an interesting QE that was for sale on eBay by Heritage. When I posted about it on the NGC forum most folks thought the look came from uneven alloy mixing.
