Stonehenge Dacite Group D: fact or fiction?

A group of six samples of an unusual dacitic volcanic tuff found close to Fargo Plantation at the western end of the Stonehenge Greater Cursus, but from unsecured contexts, had been dismissed as being a localised adventitious anomaly and probably not related to Stonehenge. However, the recent realisation that further examples had been excavated from Aubrey Hole 16 in the 1920s and found beneath the turf within the Stonehenge Circle before 1885 has prompted a reexamination of all the lithics and of their relationship to the circle.The samples examined are a heavily albitised dacitic tuff with a distinctive petrography and geochemistry unlike any other material from Stonehenge, including all of the sampled orthostats. They show remarkably little variation suggesting a common source and that some, perhaps, were taken from the same large stone.It is proposed that they represent debitage from an unknown, unsampled, buried or lost orthostat and should be considered a true bluestone. Although the precise geographical provenance of the tuff is yet to be determined, the rock is most likely from the Fishguard Volcanic Group in the north Pembrokeshire area of west Wales.