This substantial triangular stone measures 1.47 metres at its widest point, standing 1.16 metres tall and 1.1 metres deep, with a thickness of about 25 centimetres. The rock's placement at the top of the cultivation level on west-sloping ground suggests it may have been repositioned from its original location when it was unearthed.

What makes this stone particularly fascinating are the six cup marks carved into its surface; shallow, circular depressions that were pecked into the rock thousands of years ago. Two of these cup marks are surrounded by carved rings, and one of these ringed marks features an unusual tail or groove extending from it. These markings are classic examples of prehistoric rock art found throughout Ireland and Britain, typically dating from the Neolithic to the Bronze Age periods, roughly 4000 to 1500 BCE.

Cup and ring marks like these remain one of archaeology's enduring mysteries. Whilst similar carvings appear across Atlantic Europe, their exact purpose continues to elude researchers. Some theories suggest they served astronomical or territorial functions, whilst others propose they held ritual or spiritual significance for the communities that created them. The Carrowmullin stone, now residing somewhat incongruously in a residential garden, serves as a tangible link to Donegal's ancient past and the artistic expressions of its earliest inhabitants.