Just some food for thought. These photos show Newgrange before, during and after the restoration/conservation work which took place during the archaeological excavation of the mound in the 1960s and 1970s. On top is a picture of the monument as it appeared before the archaeological work. The second picture shows the giant concrete wall which was added to the front of the mound. The main purposes of this wall are to prevent cairn slippage out over the kerbstones, which had happened previously in the Bronze Age, and to securely fasten the white quartz and granite cobble stones which form the modern facade. These stones were found to be on the ground, beneath the cairn slip material. The archaeologist deduced from experimentation that the quartz had to have been placed on the front of the mound in order to have ended up underneath the cairn slip material. Interestingly, some kerbstones had fallen over as a result of the cairn slippage. There was no quartz underneath the stones that had fallen over!