I agree with Galen.
I've seen opals (synthetic?) used inside marbles to good effect. And metal. I don't know what terminology is used for that type of inclusion.
I believe the word sulphide refers specifically to the clay figures. I did some research for how the name "sulphide" came into use. My best guess so far, obtained with the help of some paperweight collectors, is that it came to us from the French, as "sulfure", in the early part of the 1900's.
Inlaying porcelain in glass appears to go back to the late 1700's. Other items such as ivory go as far back as 1584.