Block of Emerald

Blocks of Emerald is a mineral block that does not appear in normally generated maps anywhere. Although their primary usage will be decoration, they can also be used to store Emeralds. To acquire a single emerald block, one must craft a 3x3 emerald row in a crafting table.

History
On May 28, 2012, Jeb tweeted an image, featuring a room containing Redstone Lamps and Blocks of Emerald.