Geophysics has revealed that thiis is not a chambered cairn but more like Silbury Hill, as with a site at Dunragit in Dumfries and Galloway, the BA cist and animal bones from ?feasting towards the top being later additions http://www.orkneyjar.com/archaeology/saltknowe.htm
It's in a terrible state, what were rabbit scrapes is now an extensive burrow system - it would be better excavated before it becomes a complete unstratifiable mess
Behind the Ring of Brodgar in the RH corner of the field there is a cist-like structure at the top of this mound, though all I could locate on my visit was the turf-covered edge of a long horizontal slab at the side facing the loch. During an excavation nine pieces of silver 'ring-money' were found.