What Causes a Coin to Tone?

Justin

I am thinking about buying 1986 PCGS Graded MS69 $50 American Eagles. Can gold also tone?

TomB

If you utilize the "Search" button and look for threads on toning you will find a great deal of material to read, some of it is even useful and accurate. I'll let you do that instead of starting a big thread on toning. Gold also tones but does so at an extremely slow rate since gold is a very unreactive metal. The impurities in gold, principly silver or copper, will tone at a faster rate. However, unless the planchet metal is not made properly, you will likely not notice toning on a modern gold coin. If you are worried about the coin toning you can either do nothing, as you probably do not need to do anything, or you can buy an Intercept Shield holder for a slab and place the slab in the holder.

nwcs

Yes, coin gold can tone. That is because it is only 90% gold. The 10% copper does the toning. Pure gold will not tone. But if you see toning on gold coins, think of it as a warning sign. Almost all toning on gold coins (other than a slight mellowing of color due to copper or brown spots caused by a bad alloy mix) is artificially placed on there, based on the information I have.

dorkkarl

heh heh heh, pure gold will tone, but not exposed to normal air (at least, not in our lifetime). for all intents & purposes, what they said is correct, though, it won't tone, the impurities mixed w/ it will. hence the infamous "copper spots" found on many gold coins. in 20 years, i have never found a gold coin w/ vibrant rainbow colors.

K S