I bought some tubes of semi-raw Boulder Opals. All the unset Opals I could find were made to mounted flat, and none of them would have worked for wire-work. I am so happy to have found these tubes. (They still weren't cheap. Bah!) Now I need some thinner & softer wire.
Here's attempt #1 at wrapping:
Boulder Opal wrapped in Sterling Silver
(It's about 1cm wide and 1cm tall, so it's pretty tiny.)
Here are two shots of the tubes, before I pulled the Opals out.