That quality is not the result of any deliberate craft. It is evidence of the extreme heat these materials were once exposed to, heat intense enough to transform ordinary riverbank clay into something almost ceramic. The curious thing is that this material is not where it was originally used. It was pushed here, most likely by a bulldozer during a field clearance, and now sits displaced in the water as a kind of accidental archive.

What the riverside scatter appears to represent is a fulacht fiadh, a class of prehistoric cooking site found across Ireland in considerable numbers. The typical fulacht fiadh consists of a horseshoe-shaped mound of burnt and fire-cracked stone, accumulated beside a trough or pit. Water in the trough was heated by dropping stones from a fire into it, and the cracked, spent stones were then discarded to the side, building up the characteristic mound over repeated use. At Lissooleen, the burnt stone and scorched clay that would have formed this mound were apparently bulldozed into the adjacent river during the same field clearing exercise that created a nearby earthen mound, scattering the evidence across the riverbed rather than leaving it in its original arrangement. A survey of the Lee Valley area carried out in 1996 and 1997 by Michael Connolly recorded the site and noted the near-pottery hardness of the clay as a marker of the intense heat once applied there, confirming the fulacht fiadh identification despite the disturbance.