>>can you make a note of exactly what it is layered with and let me know?

Newgrange is layered with sods of turf, 'turves', stripped from the ground near the mound,also possibly brought some distance and laid down over loose clay and gravel, probably to keep the mound from slipping. There was also a few layers of larger stones between the layers of turves. I have a photo of the layers visible in the cross section of the Knowth mound and I'm pretty sure it was constructed the same way. I'll dig through my photo library and see if I can post a few of the Knowth cross sections.