This picture shows the view of the fallen stone taken at right angles to the previous shot. The base section is lying to the left of the upright pillar. The middle section is embedded in the ground to the right of the base section. The top section is off the picture to the right.
Look closely though at the end face of the base section of the stone. It seems extruded almost, like three slender fingers fused together but retaining a ribbed shape.... Once more I must express the opinion of an uninformed amateur but that doesn't have the 'look' of a natural rock. But if it was worked then I don't know what it was intended for.
E-mail me if you have any ideas about this rock (or any stone circle) which don't involve aliens. :-)