On the 1947 revision of the Ordnance Survey six-inch map, a hachured feature sits in the undulating grassland of Thornfield in County Galway. Hachures are the short radiating lines cartographers used to suggest slope or depression, and on older maps they can mark anything from a rath to a collapsed souterrain. This one, it turned out, was a disused quarry, confirmed when someone went to look in 1992.

The quarry dates to after 1700, which places it firmly in the era of organised land improvement and estate building rather than in any prehistoric or early medieval context. Post-medieval quarries like this one were working features of the landscape, dug to extract stone for field walls, farmhouses, or estate infrastructure, and then simply abandoned when the work was done or the need passed. Because it falls outside the pre-1700 boundary that defines archaeological significance for formal survey purposes, it occupies a peculiar administrative limbo, old enough to have vanished from living memory and to warrant a cartographic mark, but not old enough to be anyone's professional concern.