I don't think it's too far-fetched that certain flora could/would coincide/covary with gold in some areas. Probably not related to the gold directly, but some co-occuring mineral that a certain plant would prefer.
One has - somehow - been exposed to more sulphur (airborne) than the other.
My guess is one has been underneath the other or somehow covered or maybe stored in one end of a container opposed to the other coin.
Exposure to light may also play a role.
Gold-Silver ratio has been pretty stable the last 3 years. (https://www.bullionbypost.eu/price-ratio/gold/silver/3year/)
Prices went up same time as gold. I'd say that it looks like silver found it's level for some time to come.
My guess (and I know practically noting) is that the current...
Just a guy intrigued by PM's with an ambition to stack and learn about techniques etc.
Sadly, in Denmark there's heavy taxes on most PM's, and feedstock and supplies are severely scarce/restricted.