how much does a mason usually charge to stone a fireplace?

a gazillion dollars
depends how many pounds of weed he requires to get the fireplace nice and stoned
Im not sure but I am thinking it would depend on the kind of stone you want and the size fireplace that you have. Guessing 500-1000 dollars. I do hope that you can get it cheaper!
This is an area that if you can not do it yourself then, usually the best rock mason will cost you the most money. Be sure to ask for their work guarantee in writing, a good mason will have a contract with such things in it.
The punishment for adultery in some Muslim countries is 'stoning'. However a mason does not necessarily perform the act of stoning. "Stoning or lapidation is a form of capital punishment in which the criminal is put to death by having stones thrown at him or her. The size of the stones is usually chosen so as to prolong the victim's agony. [citation needed] The throwers are often members of the victim's family, or the larger community, which stands in contrast to the concept of a judicial executioner. Crimes sometimes historically punished by stoning include prostitution, adultery, and murder. In Judaism, and later Islam, stoning was prescribed as the atonement or punishment for a variety of sins in religious texts. Stoning as a form of capital punishment has not existed in the Western World for centuries (if at all)."
depends on what size of stone or fake stone and how much your willing to help and on the size of fire place