Stone fireplaces accumulate soot just like any other fireplace surface. The stone, however, is a porous surface that requires bit of a deep cleaning to entirely remove the soot residue. Using harsh chemicals can sometimes damage the stone, and when you read the back of many commercial cleaning ingredients you will notice the "flammable" label. This means that when fire comes into contact with the cleaning residue, a fire could potentially start, making it dangerous to use this type of product to clean the stone fireplace.
Fill a bucket with 1 gallon warm water, 1/4 cup dish soap and 1 cup oxygen bleach.
Line the floor underneath the stone fireplace with dropcloths to prevent cleaning solution from seeping into your floor.
Dip a cleaning brush into the bucket, and scrub the solution into the fireplace stone. Continue scrubbing, dipping the brush back into the solution as needed as you work your way across the fireplace.
Rinse off the brush and rinse out the bucket. Refill the bucket with clean warm water.
Drench a towel with the water and then wring the water out slightly. Wipe the towel over the whole stone fireplace to remove all of the cleaning residue, and let the stone air dry.