Is Bitumen the Key to the Quality of the Monasterboice Stone Crosses?

The tenth-century high crosses at Monasterboice, with their remarkable panels of stone carving, are unusually well preserved compared with other monuments of the time. A clue to their durability recently came to light during examination of fragments of a small cross discovered at the site that are carved from sandstone impregnated with bitumen. If the major crosses at Monasterboice were carved from the same sandstone, as seems likely, the quality of the carving and its state of preservation might well have been enhanced by the bitumen acting as a weak binding agent and as a water repellent.