I've been going through the name database here because I'm revamping my list, and recently came across
Opal again. It struck me as being quirky and pretty in an unusual way. I'm not sure if I'm going to add it to my list just yet, but it would certainly make for an unexpected gemstone name. I think the stones themselves are really pretty, too. I think it would work either as a first or middle name.
Opal Athena is regal and beautiful.
Opal Rosalie is not quite as successful for me- it is overly girly and lacks strength.
Opal Eloise is rather melodic.
Opal Veronica is a nice balance between cuteness and strength.