yeah it is hard to find anything on there but they sale it for 5.00 a pound and it is a mixture of coral pieces and things like that to kick start your reefs
yes for the coraline it is but you may have other thing to start growing too plus you may have a few living things in there also...(shrimp and things like that)
what they do is take live rock and crush it into a fine substrate. that way you are getting all the corraline spores, micro organisms,bacteria, etc etc... to seed your tank.