if you have any lapidary shops near you i would check with them(rock shops)
that were i get my slabs from,they also have nodules of other rocks etc
atleast the one i go to does
as far as how hard it is to knapp
well it is glass so if you dont do it right it crumbles
it is good for a beginner(its what i learned on and still use occasionally)
i find other types of rock dont crumble as easy,but are harder to work
price varies by the type of obsidion
good luck
