This mod allows you to convert soul gems at a smelter.

It ONLY allows you to deal with unfilled gems.
NOTE : This does NOT restrict the break down of soul trapped gems. I have not found a way to restrict these yet. Still looking for this resolution, however.
Properly assigned, full gems (Such as bought gems, found gems, or filled gems from my Soul Token mod) are not touched by this.


This allows you to break down larger gems into smaller ones.
This allows you to smelt smaller gems into larger ones
This allows you to develop petty gems from soul gem pieces
This allows you to convert black soul gems to grand, and grand to Blacks


Enjoy

If you want to use this in your mod, then get my permission.
(It's only fair.)
If you want to make your own based off this, then go for it.