When i unboxed the crucible i first thought it was made out of metal. It was polished to such a glossy finish..
Used it acoupl of times now and it seems to work as it should. Its a crucible, cant say too much about it, altho i use this one purely for refining soldering tin (burning all the flux out of it and pouring it into a bowl of water).
I did leave it outside to cool down in -3 celcius after the melt at 235c and it cooled down without cracking.