I don't use any open flame around pearls. A simple soldering iron
(like found at Radio Shack) can be heated and touched to the metal
base behind the pearl for a few seconds. If the pearl cannot be
pulled off, just hold the iron to the base for a little longer.
Never contact the pearl with anything hot.
If you're dealing with costume (pot metal) jewelry, you may find
the metal base melting with exposure to the soldering iron. Hope
this helps, Judy in Kansas