Reading the stone descriptions, I think there's been a mistake.
That's not natural opal; it's opalite, which is a manmade glass. Natural opal would be way, WAY more expensive and far too soft for use as a die.
Also the varying hardness of the stones is a big concern at this rate, damaging stones over time because the owner shuffles/shakes them in their hands before casting. The same reason why a lot of crystal confetti doesn't work out.
I'm also confused, the picture for the goblin die is definitely not hematite. It's pretty, but hematite should be solid metallic dark gray.