The Pharos siteworld was a planet in the Marrat system, in the Marrat Nebula. The planet was rich in extremely pure dilithium, so much so that if it were to have been mined it would not have required any form of refinement. This was not discovered until the 2250s when the planet became the location of Starfleet's Project Pharos. The Starfleet scheme involved building a giant galactic lighthouse on the planet, to act as a navigational aid in the dangerous region. It was while digging the foundations for the project that the rich dilithium deposits were discovered.