Coarsegrained but very strong firebricks are also made of the waste of china clay works.
Among such substances are fireclay and firebricks, certain sandstones, silica in the form of ganister, and Dinas stone and bricks, ferric oxide and alumina, carbon (as coke and graphite), magnesia, lime and chromium oxide - their relative importance being indicated by their order, the last two or three indeed being only of limited use.
Among the chief localities are the neighbourhood of Stourbridge in Worcestershire and Stannington near Sheffield, which supply most of the materials for crucibles used in steel and brass melting, and the pots for glass houses; Newcastle-on-Tyne and Glenboig near Glasgow, where heavy blast furnace and other firebricks, gas retorts, &c., are made in large quantities.
The red firebricks known as Windsor bricks, which are practically similar in composition to soft red sandstone, are of this character.
Carborundum was applied by Engels in 1899, firebricks being washed with carborundum paste and then baked.