Clinker is a general name given to waste from industrial processes - particularly those that involve smelting metals or burning fossil fuels. Clinker often forms a loose, black deposit that can consist of coke, coal, slag, charcoal, grit, and other waste materials. Electric phosphate smelting furnace in a TVA chemical plant (1942) Chemical reduction, or smelting, is a form of extractive metallurgy. ... Coal Coal (IPA: ) is a fossil fuel formed in swamp ecosystems where plant remains were saved by water and mud from oxidization and biodegradation. ... Slag is also an early play by David Hare. ... Charcoal is the blackish residue consisting of impure carbon obtained by removing water and other volatile constituents from animal and vegetation substances. ... Look up grit, GRIT, grits, GRITS in Wiktionary, the free dictionary. ...

Clinker may be reused to make hard paths.