FYI,
Some rocks can hold gases deep in them, so boiling could cause an explosion. To reiterate, I said could.
I rinse mine at the sink, using brushes I bought specifically for using on aquarium stuff then load them into the dishwasher and let it go through a wash, without soap of course.
Or, soak them in a bucket of water for a few days, scrubbing them off every time you change the water.