Aur X was a planet located in the Aur system near the Colonies planet Phu. The planet occupied the tenth orbital position within its star system and consisted of a giant diamond the size of a terrestrial world. It was believed that Aur X, as well as Aur IX another diamond planet in the same system, were originally the cores of gas giants. Along with the cloud of diamond fragments that occupied the eleventh orbital position in the Aur system, the planets were collectively known as the Aur Diamonds, and thought to have been creations of the ancient Celestial species.