I've been wanting to create a material that attempts to mimic the look of a white opal gemstone. The biggest issue I am having is figuring out how to effectively create the streaky rainbow effect on the surface. I want the streaks to have a color-shifting look that reacts to light similar to holographic materials, and it needs to be isolated out by a noise texture mask. Any suggestions would be welcome.
Some examples of what I'm trying to achieve:
EDIT: I hunted around online and I found this post: https://blenderartists.org/t/opal-material/1156421/13
There is a user named JettG_G in the comments that posted a .blend file for a procedural material that pulls of the look of a polished opal incredibly well. I'm including the link to the post in case anyone is interested in the material.