First appearing in season 8's Citizen Joe, the Ancient long-range communication stone is a device capable of connecting two people over a great distance. The prop returned in season 9's Avalon Part 2 where it was explained that the stone had greater potential when paired with a long range communication device. In Stargate Atlantis the stone was also used in a limited capacity in season 5's Identity. It wasn't until the spinoff series Stargate Universe that the stone became a major part of the Stargate story line.
In Stargate Universe, the Icarus Base was equipped with a collection of 5 communication stones along with a Earth-made long range communication device. After becoming stranded on the Destiny, the Icarus personnel used the stones extensively to communicate with Homeworld Command on Earth. The stones appeared throughout both seasons of SG:U, and played a prominent role in the story.
The prop itself is a triangular shaped piece, with rounded edges on all sides. Made from solid reson, the prop feels substantial despite it's small size of just 2.5" in length. It is adorned on the sides with characters from the Ancient alphabet, and also features the same along the top. The top also includes several Ancient patterns and two deep grooves which extend from the front to the rear of the prop.
The color of the prop varies depending on the lighting conditions of the set on which it was used. In the SG1 episodes the prop appeared black due to the mostly indirect lighting. In Stargate Universe the strong interior lighting of the ship and the long range communication device caused the prop's bluish purple undercoat to reflect brighter. It is also possible that the SG1 and SGU versions of the prop received different finishes, although this would be difficult to prove without a side-by-side comparison of both original props.
We were able to use a mold of one of the original stones to create a perfectly accurate replica. The SG1Props replica includes all of the surface details of the original stone since it is a direct copy of one of the original props. The paint scheme has been carefully matched to the original, and as such appears dark from a distance, but reflects bluish purple when exposed to the appropriate light source.