It might be wicca or pagan. We use holy water as well as believe that stones have powers. I have never heard of that exact ritual but there are many branches so of course I wouldnt know everything. I can ask around my site and see if any other paths do that. Also, black is used in Wicca to banish things (but it could also depend on the powers of the rock). Now mind you we are encouraged to make up our own rituals and spells using basic knowledge of what a color, stone, herb etc. does.