Blue Sapphire Elemental Gem

Wondrous Item, uncommon

This gem contains a mote of elemental energy. When you use an action to break the gem, a water elemental is summoned as if you had cast the conjure elemental spell, and the gem's magic is lost.

DM NOTE: In RAW the Blue Sapphire gem summons an air elemental, while the Emerald gem summons a water elemental. I thought swapping the gems made sense as blue is more commonly associated with water and green is a relatively common color for wind/air.
Source
Dungeon Master's Guide p167

Rarity

uncommon