It measures roughly sixteen metres from north to south and twelve from east to west, rising only about ten centimetres above the surrounding soil. What makes it unusual is what it is made of: burnt material, the accumulated debris of a practice that was once widespread across prehistoric Ireland and yet remains, to most people, almost entirely unknown.

This is a burnt mound, a class of monument found in considerable numbers across Ireland and Britain, typically dating to the Bronze Age, though some examples span a wider range. The general interpretation is that they represent the spoil heaps left behind by a form of communal cooking or processing, in which stones were heated in a fire and then dropped into a water-filled trough to bring it to the boil. The cracked and fire-shattered stones were then discarded, and over time, repeated use of the same site built up a characteristic mound of blackened, heat-fractured material, often with a distinctive horseshoe or kidney shape when viewed from above. The specific history of this example at Coolvallanane Beg, beyond its physical dimensions and agricultural setting, is not documented in detail, but its presence on a gentle south-facing slope is consistent with the broader pattern: such sites often occur near water sources and on ground that would have been accessible and sheltered.