Star Stones were sets of stones that were set at every Weyr. They were used to track the path of the Red Star as it approached Pern. One of the stones was called the Eye Rock; when the Red Star could be seen through the Eye Rock, that meant a new Pass was near.
The Star Stones were developed at the end of the First Interval, when the leadership of Lord Holders, Weyrleaders and Craftmasters realized the need for a way to preserve information on how to recognize the coming of a Pass for future generations. Jemmy, a student at the College, came up with the idea. Before the Second Pass started, the Star Stones were installed at all six Weyrs by Head Engineer Kalvi.
At the end of the Eighth Interval, Benden's Weyrleader F'lar invited Lord Holders and Craftmasters to view the approach of the Red Star through Benden Weyr's Star Stones. After the discovery of AIVAS, it was noted that Pern's dating system was inaccurate, as the Red Star's orbit was not exactly 50 years. In light of this, the Pernese noted the importance of the Star Stones, as it meant that a Pass could be predicted accurately despite any inaccuracies in dating.