Uses
Emerald shards can be crafted into emerald pieces by right clicking with 8 of them in your hand. 8 emerald pieces can be right clicked into a vanilla emerald, using a total of 64 emerald shards, which can then be combined into an Emerald Block, which can then be placed.
8 Emerald Shards will create 1 Emerald Piece
8 Emerald Pieces will create 1 Emerald.
9 Emeralds will create 1 Emerald Block.
A single Emerald Block requires 576 Emerald Shards.
Drops
Emerald shards are sometimes dropped upon the death of a mob as well as upon destroying the top layer of a mystic shrub or an energized mystic shrub.