The site country rock is greywacke and shale of Llandovery age (Silurian). There may be dykes of porphyrite in the near vicinity. This stone, with altered country rock, is worked at Tongland Quarry, 3/4 mile due south of the site.
It was not possible to visit the site during the excavation; the identifications are of samples taken from features on site by the excavator. Samples were supplied from:-
a. outcrop to west of the site and recorded by Coles as one of an outer arc of low standing stones
b. outcrop to north of the site and recorded by Coles (1895) as one of an outer arc of low standing stones
c. two samples of the cairn material
d. one sample from the cairn kerb material