Its flakes OK but its very easy to crumble on your edges. Also on most coral heads there is only about 1 1/2 inches of good rock on there outer edges of the head. This is what you spall off then you have a spall with concrete on one side and gnarly crust on the other side and hiding some were in there is some very nice stuff.
It is defiantly not a beginner rock but makes one hell of a point if you can pull it off. Also i think this stuff will get sharper them most flints i have used before.