The emeralds can be imbued by a druid. The imbued emerald is used in smithing to make an emerald shard which can be used for Fier'Dal fletching (Blessed Mithril Arrows)
These are used by Wood Elf and High Elf Tunare Following Smiths and Tailors to make the Fier 'dal (Wood Elf) and Koada'dal (High Elf) smithed items and Mithril Leathers
They can be Imbued by Tunare Druids and Clerics using the Imbue Emerald spell which can be scribed at level 29 and is sold at the Cleric Guild in Felwithe