It is lozenge-shaped in plan, meaning its cross-section forms a broad diamond rather than a simple rectangle, and it is orientated along a northeast-southwest axis, rising to a definite apex at the southwestern end. That deliberate geometry, so precisely maintained across millennia, is what separates a standing stone from a rock that simply happens to be upright.

The stone measures roughly 0.6 metres by 0.4 metres at its base and stands approximately 2 metres tall. It has suffered considerable spalling over the years, a process by which the surface of the stone flakes away in layers, likely due to frost action and weathering working into natural fractures in the sandstone. At its base there are low hummocks, and several smaller stones on the southeast side that may originally have served as packing stones, wedged in to stabilise the upright when it was first erected. Standing stones of this kind are broadly prehistoric in origin, though rarely dateable without associated archaeology, and their precise function remains genuinely uncertain. Ritual, boundary marking, and astronomical alignment have all been proposed, sometimes for the same stone. The northeast-southwest orientation here is worth noting, as this axis broadly corresponds to the directions of midsummer sunrise and midwinter sunset, though whether that was intentional at Garryduff is unknown.

The stone commands open views in most directions from its hillside position, the southern aspect being the only one blocked by the rising ground behind it. The upland pasture setting is rough and unimproved, which gives some sense of how isolated and deliberate the original placement must have felt.