Properties and significance:
- It can withstand a temperature of at least 1515 °C.
- It is made up of 65% siliceous materials and 22% argillaceous materials.
- It has high alumina content and kaolinite.
- It is plastic in nature and have high iron impurities.
- It is ideal for lining surfaces exposed to high temperature.
- It is used in furnaces, kilns, in manufacture of crucibles, fire bricks, saggars and glassware.