54O'Kelly, Michael J., and Claire O'Kelly. Newgrange: Archaeology, Art, and Legend. London: Thames and Hudson, 1982. 72.
The author states, "It had become obvious that the quartz/granite made up this surface at the front of the mound and that elsewhere selected boulders of the normal cairn material had been used, that it had been built on top of the kerb as a revetment and that when it fell there was nothing to hold the cairn behind it in place."