Emerald

An Emerald is an item which will be added in the 0.9.0 update, obtainable by mining emerald ore. On the PC and Console editions, it is used for trading with villagers. But, as villagers will have degraded AI, trading will not be possible, so it's only function would be to craft an emerald block and use it as a decorative item.

Trivia

 * Emeralds will serve no main purpose in Minecraft PE as trading will not be available.
 * Emeralds were added in an earlier update as well, but were removed.