Ravinder from India once drilled a series of small holes in a 6’ deep block of marble. He inserted feathers and wedges in each hole and hammered a little on them each hour for a couple of days. Sure enough, the stone developed a crack through the 6’ resulting in 2 blocks.
In marble, determine the bedding plane or grain direction. Drill the holes, insert the feathers and wedges and hit them sequentially. Most times the stone will split quickly. If not, wait a few hours or overnight before proceeding to allow the crystals to line up