The standing stone, which is believed to date from 3,500BC, is considered an extremely important national monument and features extensively in ancient texts. The granite stone is associated with the inauguration rites for the Kings of Tara and was moved to its current position in the early 19th century.
The monument was reported to be damaged last weekend, but it is unknown when the attack occurred.
An archaeologist from the National Monuments Service examined the monument this week and concluded it had been struck – possibly with a hammer or similar instrument – at 11 places on all four faces of the stone. Fragments of the standing stone were also removed.
There is a picture of some of the damage up on Facebook (the picture is public); the blows to the stone are quite clear, and while they're not so damaging that the monument itself is damaged beyond repair, the damage they've done to a monument that's probably a good 5,000 years or so is irreparable. It could just be mindless vandalism, but more worryingly (as far as I'm concerned) is the idea that the vandalism is the result of souvenir hunters trying to get a few pieces to keep or sell.
Whoever did it, I hope their disrespect comes back to bite them in the arse.