The quartz was almost certainly deliberate, placed there by Neolithic builders who seem to have favoured the white stone at passage tombs across Ireland, most famously at Newgrange. Here, though, on a modest hillside in south County Dublin, the effect is quiet and largely unnoticed. The cairn at Crockaunadreenagh, at the point known as Knockaniller, measures roughly thirteen metres across and stands about two metres high, defined by a ring of granite kerbing that still holds its rough circular form despite centuries of collapse and encroachment.

A passage tomb is, broadly, a prehistoric burial monument in which a stone-lined passage leads to one or more chambers, all covered by a mound of earth or rubble. The example at Knockaniller follows this general tradition but is described in the archaeological record as having an undifferentiated chamber, meaning the passage and chamber are not clearly distinct from one another. The interior space runs northeast to southwest, narrowing toward the north end, and measures four metres long by just under two metres wide. No roofing stones or sill stones remain visible. Fieldwork cited by scholars including Kilbride-Jones in 1950, Michael Herity in 1974, and Christopher Mount in 1988 has documented the site over several decades, and it was recorded in detail by Geraldine Stout and Padraig Clancy. A field boundary cutting across the southwestern edge of the mound has truncated the cairn at some point, a common fate for monuments that sat within working farmland for generations. The site is protected under a preservation order first made in 1940 under the National Monuments Acts.

The tomb sits to the northeast of two related monuments at Knockaniller, a second passage tomb and a ring-barrow, a low circular earthwork typically associated with burial, making this a cluster of prehistoric activity on the same hillside rather than an isolated find. Furze, the dense thorny shrub also known as gorse, covers the southern section of the site and can make close inspection awkward depending on the season. The monument is on private land on the slopes of Saggart Hill, and the surrounding area, while relatively close to Dublin city, retains a quietly rural character. Anyone with a serious interest in visiting should check access arrangements in advance, and approach the site with the understanding that what remains is a heavily robbed and partially obscured cairn rather than a well-preserved chamber.