The main raw materials used are quartz, sand stone etc. the siliceous rock is crushed and ground with 2% lime and water to form a thick paste so formed is moulded into bricks either manually or using a machine-press after which they are heated to about 1500 0 C for 24 hours.
Cooling takes about 1 or 2 weeks.
During heating quartzite converts into crystobalite which during cooling gets converted into tridymite, such that silica bricks are the mixture of these two.
- Glass furnaces
- Roofs of electric and hearth furnaces
- Lining of acid converters etc.