The Pizza Canopy, and the Pizza Stone that goes inside it, are made from a synthetic refractory  mineral that I call OBDURITE.  The name comes from the Latin word “obduro”, which means:  to make hard,  to persist, to endure, unbending.  I have been working on this formulation for about 3 years now.  It has to be rock hard and it has to be able to withstand high temperatures repeatedly,  without weakening. Nature has been  using these same materials to make lava, rocks and mountains since the beginning of time.  Most of the raw materials that make up OBDURITE have been used in the production of ceramics for centuries and are fairly inexpensive.  Unfortunately there are a few of the dozen or so ingredients that are very expensive and without which the end product would be far less lava-like.   Its not only the raw materials that make OBDURITE what it is, the process is all important.  The reactions that occur when these natural  raw materials are brought together with water and properly cured, are very “time” and “temperature” sensitive.  The process, which takes nature millions of years to do, is reduced  to about a weeks time.    I have yet to get one of my kilns hot enough to melt one of these pizza stones, but I think the melting point of OBDURITE is somewhere above 2500  degF.