Clear ornamental rock sealant???

[Backfromthedead]

I want to put this amethyst in one of my new tanks im setting up, but im worried about crystals chipping off/eroding.



Any recommendations for some kind of non toxic sealant i could coat the outside of it with that wouldnt compromise its luster or also make it too shiny? I was thinking about spray on or wipe on polyurethane but i dont think thats aquarium safe.

Thanks!