If /u/LadyLaLas and /u/CrustalTrudger are willing, there’s another way to answer the question: share a photo of your rock, and I bet /u/CrustalTrudger could narrow down the range of places it might be from.

Depending on what it looks like the answer could be “damn near anywhere” or very specific. And keep in mind that this is very difficult to do with just one photo, and I don’t think /u/CrustalTrudger is a specialist in rock identification or the geology of Ireland. But they’ll do a better job than I would and I bet it will be interesting!

For best results take a photo in bright light with a white background and a ruler or other common object to give the scale. Crustal I apologize for asking you to do geology tricks.