Irish archaeologists Tuesday heralded the discovery of an ancient book of psalms by a construction worker who spotted something while driving the shovel of his backhoe into a bog.

The approximately 20-page book has been dated to the years 800-1000. Trinity College manuscripts expert Bernard Meehan said it was the first discovery of an Irish early medieval document in two centuries.

"This is really a miracle find," said Pat Wallace, director of the National Museum of Ireland, which has the book stored in refrigeration and facing years of painstaking analysis before being put on public display.

"There's two sets of odds that make this discovery really way out. First of all, it's unlikely that something this fragile could survive buried in a bog at all, and then for it to be unearthed and spotted before it was destroyed is incalculably more amazing."