Mana Divining Stone

When used, the Mana Divining Stone allows the tracking of Ancient Mana nodes, through a buff, on the minimap while in Suramar.

You do not have to keep the stone and can delete it, however should you accidently cancel the buff, you will have to ask First Arcanist Thalyssra for another stone.

Source
This item is provided and kept when accepting Ancient Mana (quest).