This charm stone foretold the fortunes, both good and bad, of the Clan Chiefs since the Battle of Bannockburn.

The story goes that Duncan and his men stopped on the way to Bannockburn. Next morning, when his standard was lowered, the hole in the ground brought to light a ball of rock crystal, two inches in diameter and having magical powers that helped in the battle that followed. The other versions of the story have Duncan finding the stone from the hole left by his standard.

It is said to change colour according to the outcome of an impending battle and it has been used as a healing stone by dipping it in water to be drunk as a cure.

As the end of the nineteenth century Struan left it at the Museum of National Antiquities, but now it may be seen in the Donnachaidh Museum.