The block below is odd. If the top was cut off, why is the upper surface so rough? It looks like a layer has been glued on.
The one below is very similar and looks to be granite, however the smooth planed surface has that black sheen characteristic of basalt.
This one is probably the remains of a granite pillar.
These are basalt but can have the appearance of granite on the chiseled surfaces.
Next time you're up on the plateau bring a rock pick and have the chips analyzed although there are plenty just lying around. [www.independent.co.uk]