The Beacon is an itemadded in the 1.4 update. Beacon Blocks, upon added to the top of a pyramid made of either iron, gold, diamond, and emerald blocks, can grant the player potion effects for a eight seconds but will last forever if the player is in range of the beacon.
Beacon Blocks can only function when they are added on the top of a pyramid, and when not being blocked by a solid block on top of the beacon. The GUI consists of a primary, and secondary effect selection screen, a material acceptance selection header, and the player's inventory. The player must place the material (iron ingot, gold ingot, diamond, or emerald) in the header to activate the effects. When the material is placed, the player is free to choose an effect located in the primary effect screen. Whenever the player is in-range of the pyramid, the player will receive the effect. The effect(s) last forever, as long as the player is in range.