Without seeing the piece,
I will take two guess's
Lead, usually very flat or a ball that once was part of a shotgun shell
Easy to smash or squish. melts in low heat (do not do indoors)
Scratches easily and show a shine (maybe chrome look) of area scratched
Gold covered in mercury, mostly shinny to the eye, could have some sort of contamination that can give a dull appearance
Miners in the old days used many pounds of mercury, didnt know or care the bad side of the metal.
Handled properly, no big deal.
Many ways to remove mercury from gold.
This is a very touchy subject.
I will not tell you how, do the research, know the ramifications and decide on your path