Thank you but it's not my coin Regarding the color my main focus was the torso of liberty; the area right above the date
It sure looks purplish to me spock. Now if you were expecting to say that I had seen a brilliant royal purple gold coin, no of course not. But that purplish color though maybe not exactly commonplace is far from unheard of on gold. And if you think about what was said in that article that Jim posted about red and purple being the colors that gold tones, it makes sense. Why ? Because red and purple while at opposite ends of the color spectrum are also right next to each other. I say that because when it comes to toning once you go through the whole color spectrum it repeats starting from the beginning - and that places red and purple right next to each other. Purple after all is nothing but a darker red. And for those who don't know it already, yes we are talking about pure gold. Gold tones.
Aren't we talking about 90% pure gold the rest copper and trace elements . I always thought .9999 gold is inert and won't tone .
Just found this on ebay: http://www.ebay.com/itm/1908-2-5-Go...31?pt=Coins_US_Individual&hash=item19ddb8c207
The comments I posted in the other thread of spock, concerned .9999 level of gold, not much less than .99oo, certainly not .900 . Once you get a good proportion of copper or silver mixed with the gold, the coloration is almost certainly a surface reaction with those metals and the environment rather than a quantum or nanoparticle type of explanation. I would limit the discussion to .99 or higher purity gold myself if you are pursuing mainly gold reactions.
The electromagnetic spectrum does not wrap around It is on a much larger continuum. Specific chemical reactions are at play in toning.
I believe Doug was commenting about the natural toning progression of color as the surface refraction layers increase from sulfides in the atmosphere being deposited. Sunnywood determined a color classification for toned coins, consisting of 4+ cycles before the thickness of the layer became the 'terminal' black color. As the cycles increase , the progression go from light gold to burgundy and then next stage goes back to the lighter colors, etc. So as toning progresses though the refraction spectrum, the color gold/yellow/gold shows up 3 times as the colors cycle through the spectrum. I think this is what Doug meant as he is aware of Sunnywood's progressions. In one of my older threads, I listed both of Sunnywood's threads he had on CU. I don't believe a person can understand toning color progressions without the knowledge contained there. The spectrum you show above is based on transmitted light, and not reflected and refracted light.
When you find a transparent coin, you can use your theory. Yes, wavelength is wavelength, but with a coin , you are looking at light reflecting off a surface and interference patterns can occur which can produce repetitive wavelengths in series depending on how molecularly thick the deposit is. Look up interference patterns on Wiki or someplace.
Here are the two threads you should read if you want to understand and they are good for those interested in the AT/NT coins. http://forums.collectors.com/messageview.cfm?catid=26&threadid=708296 http://forums.collectors.com/messageview.cfm?catid=26&threadid=708592
Yes, I was. Toning is a progressive action, it starts at one of the spectrum and moves through it to the other. Then that progression starts all over again and that results in red being right next to purple. Yeah I am aware of what he wrote. But I was talking about pure gold toning and writing about it for several years before Sunnywood ever posted his comments. Jim, you and I had been involved in several discussions about it right here on CT before that as well.
well with what Jim was saying i have a hard time saying that gold tones red and purple. i feel more comfortable with changes color to red and purple. The toning that we have for silver is very different from the toning for gold I wonder if we should give both processes the same name since its not a reaction to the same things that cause toning in silver. Just a thought.
Look no farther than that post ^ for transparency. The thin film on the coin, causing the opalescence to which you refer not by name, which is based on molecular size. Like the stuff I developed for the coatings industry decades ago. I'd really love to see some chemistry to explain the oxidation state changes (or whatever you proffer gets cycled) correlated with the colors of this repeating spectrum idea. Or if you prefer explain the particular product of particular chemical reactions causing what color schemes to cycle. I'll sit now.
