Refractory Technology
Natural silica

Is not stable at high temperature
Transforms to other allotropic forms i.e tridymite and cristoballite involving very high volume changes
Mainly contains quartz
All of these

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Refractory Technology
Quartz is

All of these
Stable form of silica upto 870°C
Converted to tridymite on firing between 870 to 1470°C
Transformed to crystoballite on heating above 1470°C

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