What are carbon spots and what is the impact to long term to the condition of the coin? Will the condition worsen over time or does it just affect the looks of the coin? WCJ
It depends, but generally carbon spots don't grow over time. On copper sometimes they do, and on nickel they generally don't.
This Morgan was given to me in this condition more than a year ago - probably closer to two years ago. These carbon spots have not changed, at least to the eye. Unfortunately someone probably sneezed on this poor dollar.
Yes, the tiny carbon deposit in the metal alloy oxidizes in the air. And while almost any dark spot on any coin is commonly called a carbon spot, in most cases it is not really a carbon spot - they are just called that. True carbon spots are most often found on copper because there is a lot of carbon in copper.
Are you sure? My understanding is that copper is copper and carbon is carbon. Pure copper would not contain any carbon, would it? (If pure copper contains carbon then I didn't learn college chemistry and geology as well as I thought.) US copper coins are made of copper and a few other metals to make an alloy but I am not aware of carbon being one of them. Can you shed some light on this for me? My understanding of why copper (and copper alloy) coins are so prone to carbon spots is because copper is highly reactive, much more reactive than other metals used in US coins.
Yes copper is copper and carbon is carbon, but just about everything there is on this planet has some carbon in it - including us. And there really is no such thing as pure copper, gold, silver or anything else. Everything has trace impurities. And as is true with any refined metal, sometimes the trace impurities exist in larger quantities than normal. And if the trace impurities become aggregated in one tiny spot of refined metal then they tend to show up.
For some reason you don't see carbon spotting on silver or gold nearly as much as you do with copper and nickel. Don't ask me why.... p.s. I agree with GDJMSP that carbon spotting is a catchall for a number of things other than carbon.
p.s. GDJMSP, IIRC (and I'm certainly no chemist), carbon doesn't oxidize into a solid -- it's called CO2, a gas at most temperatures you'll find coins at.
Sorry, hobo, but copper is highly UNreactive. It may be relatively reactive compared to platinum or gold, but compared to everything else, it is not very reactive at all. Oh! Leadfoot, what is the composition of a nickel. The ones I have are 25% copper. Need I say more?
I hate to argumentative but I disagree. I found a website - http://rg.ancients.info/guide/toning.html - that supports my statement: I have been wrong before and I am willing to admit I am wrong on this point if you can show me compelling evidence to support your claim.
Your link is not working. Try this one. http://richardbowles.tripod.com/chemistry/reactivity/reactivity.htm BTW, that says that zinc is more reactive than copper. zinc is used in our coinage. It also list copper as very non-reactive.
I'll accept that zinc is more reactive than copper (but I'll try to remember to verify this later). I do not accept that copper is "very non-reactive". Have you ever seen copper used on the exterior of buildings? Copper gutters and downspouts. Copper roofing. Copper flashing. Unless the copper is coated it will tarnish almost immediately and turn a nice green over time. Gold does not tarnish (for the most part). Take a look at the gold-covered dome on some states' capitol building (e.g., Georgia and Colorado). I can't think of silver being used on a building exterior (perhaps hardware like doorknobs and hinges) but I am sure it will tarnish although not as rapidly as copper. I have seen nickel used in exterior hardware and it does not tarnish nearly as rapidly as copper. I don't know of any exterior uses for zinc but we agree that it is highly chemically reactive.
