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.

Uses:

• Glass furnaces
• Roofs of electric and hearth furnaces
• Lining of acid converters etc.