Cristobalite
Cristobalite is a high-temperature polymorph of silica.
Since the natural resources of cristobalite are not sufficient for industrial use,
it has to be synthetised by the conversion of quartz in a rotary kiln at high
temperature (>1500°C) with the assistance of a catalyst.
Read More about Cristobalite Here - https://en.wikipedia.org/wiki/Cristobalite