Natural stone vs firebrick for thermal mass

[Wiley]

A second look at the photo you attached.... the arch over the entrance is made with Roman bricks. I wonder how old the oven is and whether it was made with recycled materials at the time of it's construction or perhaps actually dates to a time the Romans occupied the region.
Wiley

[PerryPizza]

I took down a partition in my house which was made with the same terracotta bricks & I have a pile of those too, which I was also considering using in the oven construction. The Romans were certainly here, I live next to a Roman church, though I've always imagined the bricks were made more recently. Having said that, the buildings are made with anything going - I have a round column laid horizontally in one of my walls - I have no idea what that was used for before. There's no telling how much recycling has gone on over the centuries, and will continue with me!