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 recognized 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.