Glowstone Cluster

Glowstone Cluster is a naturally generated structure that spawns commonly in the Nether dimension. It consists of a vein of Glowstone blocks.

It will be added in Update 0.12.0

Generation
Glowstone Clusters form in coral-like structures on the underside of hanging Netherrack, so they are often found on the ceilings of the Nether, where they provide luminosity.

Trivia

 * Glowstone Clusters can be created artificially be placing Glowstone blocks.