I use a lot of driftwood and stones, and some of them come from a beach (we live right at the coast, literally 5 minutes to the ocean).
In fact, everything inside my dragon's enclosure other than his food dishes and the live plants comes from the nature.
What I do for stones and driftwood:
First, I soak them half a day in water, starting with hot water (make sure the bucket can handle the temperature). After doing so, I use a heavy-duty brush. The salt is gone after that. (Might sound funny, but when I started doing this procedure, I licked on a few pieces and I can't taste anything left
)
Then I let it dry very well, I'd give it a week (but here the sun is very strong). Afterwards, the items go into the oven.
(I also use sand, which I get from the desert here, in my dragon's enclosure. Not sand from the beach!
Btw.: I'm also using a lot of stones and driftwood from the beach in various planters on the balcony or otherwise outside of his enclosure, regular house plants. For those I also use the method described as plants generally can't handle salt well. Salt is gone and the plants thrive!)