This cairn sits on top of a small, conical knoll to the south of Loch Mudle. We often check the tops of knolls partly for the view but also because foxes, pine martens and wild cats sometimes leave their scat on their mossy turf. In this case, there was nothing but a few offerings from the local sheep, but the cairn itself was of interest because, from the way most of its constituent rocks are covered with mosses, it's obviously old. While it may be a boundary marker, it wasn't on one of the boundaries of the old clachans. On Bald's 1806 map it's clearly on Tornamona land.
here, which is particularly good as it's maintained by Dr Alan Silverside of the University of the West of Scotland. From the website, it seems possible that this is P. membranacea. I don't suppose it matters too much what it's called, except that it's somehow good to have found out. What does matter is that the lichen, with the strange root-like growths under its 'leaves', is rather beautiful.