Removing jeweler's epoxy from opal surface?

All,

I had bought some “opal starters” on a road trip through Idaho this
summer, and I am actually ready to consider using one. The person I
had bought them from, told me that an opal starter is a
semi-finished opal material that is eventually incorporated in a
triplet. The opal material was attached to a rock backing and then
polished until the opal material shows. The surface was then coated
with Hughes jewelers’ epoxy as a protective barrier for temporary
storage purposes. The barrier is supposed to be later removed prior
to placing a polished glass layer on top of it.

For any of you who work with opal, what is the best way to remove the
epoxy layer, mechanically or chemically? If chemically, what
dissolves Hughes epoxy? If mechanically, what sanding/polishing
sequence?

Thanks in advance,
Andrew Jonathan Fine