Search:

Well, you used the term nomi :) That's pretty good.

A cheap hardware store chisel would do the job, though, or you could literally just build a box out of components, gluing pieces around the...

I don't think I'd use shellac as a general sealant on a stone. Shellac doesn't tolerate water and solvents that well. It doesn't get ruined immediately by water, but it gets damaged pretty quickly....