Originally posted by Zep Tepi:

They have always done damage. The raw eitr sitting on the ground will too.

In addition to black marble, Iron cage walls and floors are also safe, and of course earth walls. I stuck mine in a hole with an iron cage roof. Not pretty, but easy to do.

Didn't know about the iron cage walls and floors. Do the iron gates work? Wouldn't mind putting a door on my refinery building.