Glowstone

"Glowstone was added to Minecraft on 30 October 2010 in the Halloween Update - which also added Jack o’Lanterns, clocks and fishing. It occurs naturally in the Nether, generating on the underside of netherack, but if you’re having trouble finding it then clerics in Minecraft villages will sometimes sell small amounts in exchange for emeralds."

- Duncan Geere

Glowstone is a light-emitting block that appears in the Nether, and that can be acquired from trading.

Natural generation


Glowstone occurs naturally only in the Nether, where it generates in crystalline clusters on the cellings of netherrack.

From block loot
If a tool with Silk Touch is used, the block drops itself.

From trading
Journeyman-level Cleric villagers offer to sell one glowstone for four emeralds.

Wandering traders sell glowstone for two emeralds.

Breaking
If glowstone is broken using a tool with Silk Touch, the block drops itself. If a tool with Fortune is used, it has a higher chance of dropping a large amount of glowstone dust—but never more than 4. When a glowstone block is broken with any other tool, it drops 2–4 glowstone dust.

Light source
Glowstone blocks emit a light level of 15, the brightest possible light level in the game. They emit the same amount of light as lanterns, sea lanterns, jack o'lanterns, redstone lamps, conduits, beacons and shroomlights

In redstone circuits
When placing redstone on a glowstone block, being a transparent block, signals can pass from one block to another diagonally. Redstone wire, even though it may appear to connect up the side of a glowstone block and to the wire portion on top, does not send a redstone signal down the glowstone block. This makes glowstone effective for vertical diodes, logic gate designs, and space-efficient instant vertical redstone.

Note that upside-down slabs can be used for the same purpose, and are easier to obtain.

Note blocks
Glowstone can be placed under note blocks to produce pling sounds.

Respawning
Glowstone is used to charge respawn anchors.

ID




Trivia

 * Since glowstone blocks become block entities when moved by pistons, this momentarily stops them from giving off light. This will not be fixed.
 * Rarely, glowstone can be found touching the ground if the ceiling it was generated on was extremely low (2-3 blocks of clearance).
 * Glowstone, though being transparent, causes the sky light to count down as if it hit a non-transparent block, whilst still letting through this light.