sciencehabit writes: Kissing the Blarney Stone, which involves hanging upside down from the battlements of Blarney Castle near Cork in Ireland, is meant to bestow eloquence and persuasiveness. Such claims are not known to have been put to the test in a clinical trial, but then not much is known about the rock itself. Some say it is made of Welsh bluestone, the same material used to make the monoliths of Stonehenge. Others say it was cleaved from the Stone of Scone, which forms the coronation seat used by the kings and queens of Scotland and Great Britain for hundreds of years. Now, some light has finally been shed on the stone’s mysterious origins by the chance find of a microscope slide in the Hunterian Museum of the University of Glasgow in Scotland. Analysis of the sample, which is cut thin enough to be transparent, by geologists at the museum reveals that it is not a bluestone, nor is it sandstone like the Stone of Scone. In fact, it is a 330-million-year-old carboniferous limestone typical of that corner of Ireland and contains fragments of fossilized brachiopod shells and bryozoans.