Malachite will "
pop" off with a scalpel if the underlying condition is right.
I have done this numerous times on
silvered coins - you can see some examples in the "sticky" post about cleaning
silvered Roman coins.
However, I don't know about the surface state of your coin.
Personally I would use a scalpel under magnification and clean some of the dirt encrustations off and also try to gently pop/lift off some of the malachite - starting with small out of the way
bit. If it doesn't
work you may have to leave the malachite.
SC
