Petrological and geochemical characterisation of the sarsen stones at Stonehenge

Little is known of the properties sarsen stones (or silcretes) that comprise main architecture Stonehenge. The only studies rock struck from monument date 19 th century, while 20 century investigations have focussed on excavated debris without demonstrating a link to specific megaliths. Here, we present first comprehensive analysis samples taken directly Stonehenge megalith (Stone 58, in centrally placed trilithon horseshoe). We apply state-of-the-art petrographic, mineralogical and geochemical techniques two cores drilled stone during conservation work 1958. Petrographic analyses demonstrate Stone 58 highly indurated, grain-supported, structureless texturally mature groundwater silcrete, comprising fine-to-medium grained quartz sand cemented by optically-continuous syntaxial overgrowths. In addition detrital quartz, trace quantities silica-rich fragments, Fe-oxides/hydroxides other minerals are present. Cathodoluminescence show cement developed as an initial <10 ?m thick zone non-luminescing followed ~16 separate growth zones. Late-stage Ti-oxides line and/or infill some pores. Automated indicate preserves 7.2 9.2 area % porosity moderately-connected intergranular network. Geochemical data chemically pure, 99.7 wt. SiO 2 . major element chemistry consistent within stone, with magnitude variations being observed Fe content. Non-quartz accessory silcrete host sediments impart signature distinct standard sedimentary crustal materials. 143 Nd/ 144 Nd isotope suggest these were likely derived eroded Mesozoic rocks, rocks incorporated much older Mesoproterozoic material. has been identified recently representative 50 52 remaining sarsens at These results therefore type used build what arguably most important Late Neolithic Europe.