spot on coin getting darker & larger 0

[Timely]

I have a 1894 $20 Lib MS62 with a spot on the obverse on her hair.  In the past 2 years the spot is now twice as dark & has increased in size by 25% or so. The spot looks maroon in color.  Any thoughts? Here's the coin 2 years ago.

Edited July 10, 2019 by Timely

[Mohawk]

Well..the only thing I can think of that may help you is submitting the coin to NCS and seeing what they can do.  If you have a picture of the spot, I'd post it in the Ask NGC/NCS Forum and see what they say to you about it.

Good luck with it!

~Tom

[Greenstang]

It might be some copper showing that was mixed in with the gold. As those coins are 90% gold with other alloys mixed in, it is not unusual with gold coins to have copper showing. It doesn't really affect the grade, but does affect the appearance.

Edit;

Just did a little research and found this article

Most gold coins are between 90 to 92% pure gold depending on the country of issuance. Copper or silver are added to the gold during the melting process to give the finished solid gold coin a hardness. Although during melting the metal molecules are usually mixed well, sometimes traces of copper or silver will be collect near the surface, thereby allowing the change in color in that particular spot.

Check out my counters

Edited July 10, 2019 by Greenstang
Added copy