Netherrack (formerly known as Netherstone[1]), is a block that is found only in the Nether. Netherrack is rather fragile and can be mined extremely quickly, even using a stone pickaxe. It can also be broken relatively easily by hand; however, using your hand or a tool other than a pick will drop no material. Netherrack has an extremely low resistance to TNT and can be destroyed by the Ghast's fireballs.
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, or putting another block on top of it.
Netherrack can be used as part of a trapping mechanism for Mob farming. It can also be used to protect buildings or places from mobs, mob damage, or other players. There is a danger of flammable blocks such as Wood catching on fire if burning netherrack is too close to them, so netherrack should generally be placed far away from flammable blocks. Nonflammable blocks such as Stone can be used as a buffer between the netherrack and flammable blocks. Burning Netherrack can also be used to keep an area clear of snow/ice more efficiently than can torches due to it having a greater brightness.
Due to its abundance, and fast mining speed, netherrack also makes an efficient building material. Digging out underground quarries in the nether is a good way to obtain large quantities of netherrack quickly. Note: Netherrack is good for building functional structures, (Bridges, walls, etc.) but may look unsightly to some. If this is the case, see Stone or another block type.
It is possible to place several single tiles of Netherrack across one's outside home area and light them on fire using flint and steel. Animals will carelessly jump on top of the blocks, catching on fire, and more often than not, jumping off the burning Netherrack and dropping loot in a safe location. After a while, many animals will kill themselves on the traps and their loot can be collected for free. Be sure not to place them near trees or wood, or you may cause a large fire. Water will not evaporate if placed on a Netherrack block in the Overworld (this is a property of the Nether itself, not the Netherrack blocks).
Another type of trap can be made using Netherrack and Cacti. This can be done by digging a line around a chosen area and placing alternating blocks of sand and Netherrack, placing Cactus blocks on the sand, then lighting the Netherrack on fire.
This trap is good for placing in an open area as a perimeter for stopping Mobs. However, as of Beta 1.2, spiders are able to climb over the wall as pictured unless an overhang is added to the top of the cacti. Thankfully, this will still damage the spider; if the spider is in the sunlight this will "reset" its anger and it will become neutral.
Trivia
Moving Netherrack through the use of pistons will put out any fire currently active on top of the block. However, if the piston is pushing a line of 2 or more Netherrack blocks, fire on the block(s) in the front will be transferred to the block(s) behind it.
Netherrack, although stone, used to be able to be destroyed by hand in seconds, making it the first of its kind in Minecraft.
The name "Netherrack" is not a misspelling of "Netherrock".[2]
To find north, find an 'L' on the top left corner of the block. The 'L' always points north. It is also present on Cobblestone, but after Beta 1.7 the Cobblestone arrow now points west.
Despite being flammable, Netherrack cannot be used as fuel in a Powered Minecart or Furnace.
Netherrack can be mined in 50 milliseconds with a golden Pickaxe (or a diamond pickaxe enchanted with any level of efficiency).
A screen capture of the 1.9 prerelease "dripping" lava. This is not exclusive to Netherrack; any block "drips" water or lava when the layer is only 1 block thick and has water or lava above it.
If Netherrack is burning under a Glass block which is under a Water block, smoke comes through the Glass and the Water blocks to the air. The smoke then can light fire to burning blocks near enough to the Netherrack block. These blocks do not need to be directly over the Netherrack block.
Bugs
If Netherrack is lit and then immediately extinguished, the game freezes.
Sometimes when placed adjacent to Nether Brick, Netherrack becomes Nether Brick.