Try a purpose cleaner first and then scrubbing with mild body soap and water, intermittently applying the all purpose cleaner.
If all fails then try the below but with a warning
Mix a gallon of water with half a cup of trisodium phosphate and scrub your stone fireplace clean. This mixture is toxic though so you should make sure that you have a proper mask and gloves and that all your windows open for proper ventilations. Be certain that you have covered your other pieces of furniture or carpet.
Then make sure you discard fluid correctly