Paul- Do not put opal beads in a a sonic. Regardless of the solution
in it, the sonic can destroy them. Opals are notoriosly fragile.
Vinegar or lemon juice and salt will clean the tarnish off of the
Many detergents will discolor the brass.
If this were my project I’d separate the opal beads from the brass,
clean seperately and then re string.
Have fun and make lots of jewelry.