Glowstone

Glowstone is a Block that provides light. It can only be found naturally in The Nether, where it generates in coral-like clusters on the undersides of Netherrack. When mined, Glowstone does not drop a Glowstone block, instead shattering into 2-4 Glowstone Dust, which may then be used to re-craft Glowstone Blocks or boost the effect of a potion.

Glowstone shares many properties with Jack-O-Lanterns and Beacons, with a luminance of 15 (as compared to Torches at 14) and the ability to provide light when submerged under water. Like all non-sunlight light sources, Glowstone Blocks will cause nearby snow and ice to melt.

Glowstone can be mined more efficiently with Silk Touch Enchantment to drop actual Glowstone Blocks during mining, or Fortune Enchantment to drop four Glowstone Dust rather than two or three.

Harvesting Methods
Glowstone occurs naturally in The Nether. It can be difficult to harvest there, due to high ceilings, sheer cliffs, an abundance of lava, and dangerous mobs. Pillaring up to dense Glowstone clusters is often useful, provided there are no Ghasts in the vicinity. Glowstone sometimes appears beneath low ceilings, which makes mining significantly easier. Glowstone can also be collected by directing a Ghast's fire ball at a glowstone deposit, destroying the blocks with the resulting explosion. This could be useful if the glowstone is very hard to reach.

Witches can drop Glowstone Dust, which can be used to craft Glowstone Blocks, though Witch farming can be hazardous.

Priest Villagers will sometimes trade 2-3 Glowstone Blocks in exchange for an Emerald.

Uses
Glowstone has a higher light level than torches (15 as opposed to 14). Because it is a block, players can replace wall, ceiling, or floor/ground blocks with it for aesthetically pleasing and versatile embedded light sources, which can be especially attractive for lit paths. It can also be attached quickly to existing flat ceilings, unlike Torches. A "lamp post" of sorts can also be fashioned from a fence block with a Glowstone block on top.

Their ability to be submerged in Water affords the ability for docks or harbors to be lit from under water for a pleasing and functional effect that is useful to players in boats that need to see where to stop. Glowstone can be used as a source of light for growing crops at night, and can be placed under irrigation paths to provide an aesthetic ambient glow for crops.

Note however, you cannot place anything on Glowstone except for blocks and redstone, meaning that torches, doors, etc. cannot be placed on it.

When placing Redstone on a Glowstone block, being a transparent block, signals can pass from one block to another diagonally, with Glowstone "blocking but not blocking" it. Redstone wire, even though it may appear to connect up the side of a Glowstone block and to the wire portion on top, will not send a Redstone signal down the Glowstone block. This allows for a one-way signal without requiring a repeater. This makes Glowstone effective for vertical diodes, logic gate designs and space-efficient instant vertical Redstone.

Trivia

 * Since glowstone blocks become entities when pushed by pistons, this momentarily stops it from giving off light.
 * Rarely, glowstone can be found touching the ground if the ceiling it was generated on was extremely low (2-3 blocks of clearance).
 * When glowstone is placed 9 or more blocks above ground level (out of its lighting range), glowstone will actually cast a shadow, despite it being a light-emitting block.
 * When you break glowstone, it has the same sound effect as breaking glass.
 * In the Xbox 360 Edition, because of the lack of glowstone clusters due to small worlds, Blazes drop 0-2 glowstone dust for a renewable source of glowstone.
 * Oddly, if a piston contraption is used to move a glowstone block onto a player's head, it will give an x-ray effect. This is useful should one want to find cave systems (though will kill you if done in survival without a partner unless you are in the xbox version).
 * Glowstone was formerly known as lightstone.

Gallery
Glowstone (Block) Glowstone/es Glowstone (bloc) 발광석 Lichtsteen (blok) Jasnogłaz Светящийся камень 萤石块