Any of you guys ever have a gold coin develop them after it has been slabbed? 5 or 6 years ago I bought a St. Gaudens DE slabbed MS-62 by NGC. I don't know how long it was in the slab before I bought it. The coin had a spot on its obverse, now it appears to be developing another on the obverse and one on the reverse. I suppose they could have been there all along, but I don't remember seeing them. I know slabs aren't designed to prevent spotting from happening, but have any of you had it happen to a slabbed gold coin in your collection? Thanks
Hey Bigswick... Not really had spotting..but I sure have some nice toned gold ! It gets real deep gold and looks fake kinda..I do have a 1989 1/2 oz AGE that has a slight haze on it..but minimal. GDJ (Doug) has shown some examples of red spots forming on gold...cant remember the thread name..but it may have the key words in it "red spots" Good luck! RickieB
Rickie, Now that I think about it.....The "new" spots do appear to be more like what you described- a deep gold or maybe even a reddish color. The one previous spot is much darker, almost a dark brown or black in color. Maybe my coin is toning? Hmmm.....
Ya know..it can age like a fine Carribbean Rum...a real nice deep gold color...look for that post and I will try to post some pics of the toned gold for you tomorrow.. Later.. RickieB
The very dark or black spots on gold coins are typically there from the time the coin is struck and they have nothing to do with toning. For the life of me I can't remember what it is that causes them though.
Slabbed coins are not necessarily air tight and the grading organizations do not claim that they are. Any air seaping into a slab contains moisture and numerous other contaminates that effect metals. Although Gold is considered a very non reactive metal, it still does react with other elements. For instance if there is a high consentration of Sulfur in the air in your area due to Sulfur rich coal being burned, the air will accumulate the SO or SO2 radicals which combine with the Hydrogen Hydroxide ( water) to form an air born acid. This acid does over a period of time react with Ag (Gold) to form Au2S a rather BR/BK color. If you have a pool nearby that contains Cl (Chlorine), some of the Cl becomes air born and also could effect your gold coins by becoming dark spots of AuCl4. However, such reactions would be very noticable on any Silver coins in the area first since Ag (Silver) is much more reactive than Gold. The summation is to put such a slab into a freezer type plastic bag, squeeze out as much air as possible and seal. If none of the above helps, just get rid of the coin by sending to me free. I'll put up with a few spots.
Carl, Thanks for the chemistry lesson! I believe the closest powerplant to me is a nuclear one in Idaho, so I doubt that's it- or at least I hope not! There are a few pools around, but none near me. Our water table does have a lot of sulfur in areas and there is typically little humidity. I think the dark area is simply a carbon/copper spot (I've heard both terms used) that has probably been on the coin for years. It is roughly 1/16 of an inch in diameter. Is that considered big for a carbon/copper spot? My understanding is that they come from concentrations of copper in a given area of the coin, the result of a weak mix of the copper/gold. The spot doesn't appear to be "growing" so I guess that is good. Maybe the other two spots are where the coin is starting to tone, but I might have to wait several years before I find out for sure. Like some collectors new to slabs I did think the first few slabbed coins I bought were airtite, but I soon found out that they weren't from members of another coin forum. I'm not sure about this, but one of them even claimed that the process used to seal most slabs would create bond that was only good for about 10-15 years. That sounded a little suspect to me, but I've never owned a slabbed coin that long so, again, I'll have to wait and see- but I doubt it.
I'm not sure of exactly what a Carbon/Copper composition could or would mean. These two elements do not react, at least under normal conditions. Now there is a small amount of Copper in Gold coins. However the mixture is NORMALLY a very homogenius mixture. Copper and Gold are a mixture, not a compound. Same with Carbon/Copper if for some reason someone added Carbon to the coins original composition which I doubt the government would allow. However, since Gold and Copper are a mixture, there is a slight chance that due to some cooling procedure, a small quantity of copper could rise to the surface of a sheet of material used to produce the coins. If there is some contaminates in the air when and where the coin is slabbed, the reaction of the contaminate and the copper near the surface could begin but if no further Oxigen or other gas material is permitted to enter the slab, the reaction should cease. Again, I suggest you seal the slab in a freezer type plastic bag, squeeze out as much air as possible, and monitor the size of the spot(s) on the coin. If any growth of the spot(s) occurs, there was sufficient contaminates in the slab to continue the process. Also, note that almost all chemical reactions require high temperatures indicating that the invironment you place your coins could also have an effect on this spotting. As you know where there is extreme cold the molecular movements deminish causing chemical reactions to deminish. Again, sorry for the boring chem lesson. Oh, one more thing is not only do power stations utilize fossil fuels (coal, gas, oil) but also foundries, steel mills, fatories with large boilers, etc. Also, many large cities treat the waters from sewerage with chlorines and flourines.
