These are cup marks, the most common form of prehistoric rock art found in Ireland, small circular depressions ground or pecked into stone by people whose intentions remain genuinely unknown. Theories range from astronomical mapping to ritual offering vessels to boundary markers, but none has stuck convincingly, which is part of what makes sites like this one quietly unsettling.

The boulder at Drummin is earthfast, meaning it is set into the ground rather than free-standing, and measures roughly 2.4 metres north to south and 1.5 metres east to west. Its eastern side rises about 62 centimetres above ground level, while the western edge tapers to just 15 centimetres, giving the surface a gentle tilt. Fourteen cup marks are spread across the stone, most of them clustering toward the eastern side. Three are notably large, around 7 centimetres in diameter, though relatively shallow at about 1 centimetre deep. The best preserved of all sits near the southern end of the boulder, measuring 5.5 centimetres across and 1.7 centimetres deep, its edges still relatively crisp despite exposure to centuries of Wicklow weather. The remaining marks are smaller and more worn. There is also a suggestion that the eastern edge of the boulder may have been quarried at some point, which raises the possibility that the stone has been altered or partially worked since the cup marks were first made. Research by the Wicklow Rock Art Project, based in the School of Archaeology at University College Dublin and directed by Dr. Clíodhna Ní Lionáin, has produced a photogrammetric three-dimensional model of the stone, a technique that uses overlapping photographs to generate a precise digital surface, allowing the marks to be studied and measured in detail without further disturbing the rock.