That's what Old_School taught me, so I'll stick with it. Japanese lacquer.
But the guy at the store did tell Keiko that we don't really need that specialty lacquer and can just use any type of sealant. This rock appears very dense and does not seem likely to fall apart easily.
Not sure I will have much choice here in the States though. Will just have to get what I can.
You don't need to lacquer it at all. You can if you want to, but...really, it's not necessary.