Smythe has been playing with that thought. I don't know how it turned out. Maybe he'll chime in on this thread.
Knowing a bit about the complexity of Coticule's natural matrix that binds the spessartine garnets together, I don't think we humans can "perfect" it by bonding them synthetically. For starters, Coticule dust is not pure garnet, but the whole stone, natural binder and all, shattered into small fragments. If you're going to add something to cement them back together, you'll always end up with a stone that has lower relative garnet content.
Turning Coticule dust into a stropping compound, seems more promising to me. I've experimented a bit and got good results, but nothing that surpassed the edge I get off a whetstone.
Best regards,
Bart.