Rocks as a thermal mass in front of fireplace?

Would 200 kg of rocks (40 rocks ,5 kg each one) make any difference in front of a fireplace
fire,using these rocks as a thermal mass? I guess piling them would create air space betwween them.
Still would that be an effective way to retain some of the heat coming out of the fireplace.In front of the fireplace
is very veyr hot so wouldnt that be a good idea?

Rocks will absorb heat and act as thermal mass.  You are talking about an open fire place and not a wood stove, right?  Either way, rocks will help.  Just be sure that they are stable so that the pile of rocks is not dangerous, since this area is where you tend the fire.  Any mortar (concrete, cob, clay) would help secure the pile, fill the air gaps, and add thermal mass.  Even putting regular dirt between the stones would get rid of air spaces and increase it's thermal potential.

Roberto pokachinni wrote:Rocks will absorb heat and act as thermal mass.  You are talking about an open fire place and not a wood stove, right?  Either way, rocks will help.  Just be sure that they are stable so that the pile of rocks is not dangerous, since this area is where you tend the fire.  Any mortar (concrete, cob, clay) would help secure the pile, fill the air gaps, and add thermal mass.  Even putting regular dirt between the stones would get rid of air spaces and increase it's thermal potential.

Yeah i am talking about an open fireplace.Thank you for the answer.