Emerald Ore

Emerald Ore is a block that drops Emeralds when mined with an Iron Pickaxe or better; it does not require smelting. It's only been generated in certain biomes, at the moment it's confirmed to be generated below extreme hills and jungle biomes, and not been generated below desert and ocean. also the ore can appear at any level between 1 and 128.

History
Starting from Survival Test, Diamond was apparently going to be called Emerald.

Emerald Ore was first seen in the preview screenshot from Jeb and had a red texture; it was later released in snapshot 12w21a.

Trivia

 * Emerald Ore is an estimated 25 times more rare than Diamond Ore as of 12w21a.

Bugs

 * Jeb forgot to change the color of the ore in snapshot 12w21a, so it appears red rather than green.