A second option was to go for tethered artificial rocks made from polyurethane or polyethylene. Here there are concerns about the carbon footprint involved in their manufacture.
The best option would be to use slag remains of a coal mine. This would be similar to the Lady of The North project in Northumberland, England. However the aim is entirely different. There the aim is to produce something beautiful from the coal mine remnants. The aim here is the opposite. I want a vision that is initially dark and bleak, the heaps of black coal casting shadows over the landscape. However over the years the aim would be to allow nature to slowly reclaim the site, weeds and flowers spouting out from among the skeleton remains. This would be a metaphor for the Gaia principle in action. The bones would also be reminiscent of tumuli, ancient burial mounds found throughout the world and in this country back as back as the Neolithic Age.