yeah, but you want to look for southdown (or new castle or one of the other southdown variants)...do a search of this board for 'southdown' and it'll turn up a whole lot of info--mostly what you want is something that is aragonite so that it'll help with ph buffering. if you're unsure as to if what you got is aragonite or not, put vinegar on a small sample and see if it fizzes. If so then it's aragonite.
-leigh