This depends on the type of rock, its moisture and air components. For example, the lava stone that contains many air bubbles and is thus lightweight, will not explode and is often used for fireplace mantles. Featherrock is a national brand name of this stone.
Concrete need a uniform and compacted base, so as long as that rock is uniform and compacted, you should be fine.
BEST METHOD IS TO PRIME AND PLASTER OVER...NEED ACRYLIC ADMIXTURES ADDED TO STANDARD PLASTER PORTLAND CEMENT MIX....TO GET SMOOTH SURFACE WOULD NEED TO PUT THE PLASTER ON IN MULTIPLE LAYERS, LET DRY AND REPRIME BETWEEN LAYERS...PRODUCTS FROM COMPANY STD DRYWALL WITH ACYYL 60 SOLUTION WORK....OTHER WAY WOULD HAVE TO ANCHOR FIR WOOD STRIPS TO VOLCANIC ROCK (LONG FASTENERS) WITH FIR STRIPS LEVEL AND PLUMB USING WOOD SHIMS IF WANT TO ATTACH A NEW LAYER OF FLAT GYPSUM WALL BOARD....
Honeycomb rock is limestone rock. Little pieces of rock landed on the surface and carved a little hole for itself then with wind and water the rock switched around making the hole even bigger.
Paint them on the rock
Flip Flop Rock was created in 2003.