Refractory Technology
Quartz is

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

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Refractory Technology
Fireclay refractories

Combine with salts (e.g. chlorides sulphates etc.) & bases (e.g. lime, magnesia etc.) forming fusible aluminates silicates etc
All of these
Are not resistant to the action of basic slags
Shrink during firing

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