Currently, we have Amethyst Dust from both Tech Reborn and Hex Casting, as well as Amethyst powder from Spectrum.
We also have some odd behavior going on. I'll use the following to refer to each item:
APS = Amethyst Powder (Spectrum)
ADT = Amethyst Dust (Tech Reborn)
ADH = Amethyst Dust (Hex Casting)
Tech Reborn's grinder turns Amethyst into APS instead of its own ADT.
Create's millstone makes APS, but its grinding wheel instead makes ADT.
I'm not sure how I ended up with ADH, but I found it in my inventory after doing some of these processes and it doesn't show up in REI at all for me.
So I'm not exactly sure if it's feasible to consolidate them into a single item, but I thought as it is some of the interactions are a bit counterintuitive.