[Rockhounds] Cleaning Galena, Help?

[Axel Emmermann]

Since lead is an amphoteric element and I believe lead sulfide to be
insoluble in caustic environment (may be wrong there) it could pay to try a
caustic soda solution or potassium hydroxide.
These are pure guesses (educated guesses but guesses nevertheless) so try
out on small piece.
It depends all on what the coating is.
Lead sulfate wont dissolve in acids or bases as far as I know.
Lead oxide will dissolve in strong acids that form a soluble lead salt and
caustic soda or potash.
HCl may dissolve lead oxide slowly when hot. Nitric acid will both oxidize
and dissolve the sulfide thereby forming a new coating of insoluble lead
sulfate.
Caustic soda may dissolve the lead oxide forming lead plumbate (soluble).

Worth a try?

Cheers
Axel