Once Netherrack is lit on fire using Flint and Steel or a Ghast's fireball, it will continue to burn until it is put out, usually by the player. This property of Netherrack makes it a source of persistent light when lit on fire, thus making them popular components of fireplaces. This also allows the creation of Netherrack traps, such as firewalls. Fire from the burning Netherrack will spread to nearby flammable blocks such as Leaves. The other way round, netherrack will not get set alight from nearby fire. Burning netherrack can be put out by water (except in the Nether itself), mining the block, putting another block on top of it, or clicking its top surface (with any tool or none, but a pickaxe is likely to mine the block).