I believe that you have more “Opals” than you think William.
Each marble has to be backlit looking for a reddish/pinkish glow in the base glass.
This will show up while backlighting them as you move the marble around over the light. Some are hard to ID—just get the base glass if you can and be rewarded.
If yours is an “Opal” it is a very cool find—not really common imho.
I appreciate all opinions and hope to see some more.
Marble—On!!