The stone, uncovered by the Balfour Beatty team and identified by museum experts, displays a unique carving previously unknown in the region. The Pictish design is thought to be extremely significant as few stones carved with this particular type of image have been found in Scotland and its discovery identifies the importance of the area in Pictish times.
In line with council policy, all works stopped on site to allow archaeologists to excavate further.
The study of the carving and what it can reveal about life in Pictish Scotland will continue and the carving will be donated to a museum over the coming months.
Alec Campbell, one of the two Balfour Beatty employees who uncovered the stone, said: "Once the dig was done, we were clearing the area. We flipped the stone over to take it away and knew we had found something different."
David Strachan of Perth & Kinross Heritage Trust added: "This is a really significant find as there are very few such stones known in Scotland, it's a signal of the importance of the area in Pictish times. I would like to take this opportunity to thank the finders of the carving for drawing it to our attention.”
Following the discovery, work has now restarted on site and is due for completion next year.