The Projection Stones are a Nomai technology used for communication with a remote location. Each stone is linked to a single location. They allow characters to send written messages from one projection wall to the wall of the linked location, and to see that location's respective Projection Pool as if they were physically in that space.
When placed on the receptacle of a projection wall, the stones allowed the Nomai to send and receive written messages to the respective wall. When the player places a stone in a wall's receptacle, the wall will display the archive of the last messages that were sent through it to the stone's linked wall. If a same stone is used on different walls, it will display different archives, or nothing if the two locations were not used to communicate. The messages are color coded according to their origin: local messages are displayed in blue and remote messages are displayed in orange. A stone is usually found next to or very near a wall that used it on a regular basis.
When placed on the receptacle of a projection pool, the pool will form a full color 3D projection of the linked location as it is presently. These provide hints to important locations throughout the player's journey.
This technology allowed the Nomai to maintain long distance personal and work relationships once the two stranded tribes became reunited, and was crucial in the development of the Ash Twin Project.