The stove is covered with nicely polished Brazilian soapstone, and with the extra heat storage module that this model has, maximum heat storage is achieved, which collects and emits heat at one and the same time.
The advantage of soapstone in general is that it is a material that absorbs heat from the oven slowly, while at the same time gives off the same heat long after the fire has gone out. The heat dissipation is thus more even, and you have enjoy it for a much longer time. In addition to the visible stones, there are also built-in extra storage stones in the top section.
Especially for the TT21RS Heatorage in particular, you can feel the effect of the soapstone for up to 13 hours * after the last firing.