The Stones of Stonehenge

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Tim Darvill and Geoffrey Wainwright’s research focuses on the very stones of Stonehenge. Here, they give us an insight into their 2008 excavation at Stonehenge and ten years of fieldwork in and around the Bluestone quarries in the Preseli Hills of north Pembrokeshire.

Previous analysis of Stonehenge has focussed on its layout and construction, chronology and phasing, function, and symbolism. But Timothy Darvill and Geoff  Wainwright are convinced that there are other important aspects to Stonehenge that deserve the attention of archaeologists: the geology and character of the stones themselves.

For over two centuries it has been recognised that the mass of stones forming the iconic structure known as Stonehenge comprises several different kinds of rock. Writing in the 1720s, William Stukeley noted that all the large stones were ‘gray weathers’, or what today would be called sarsen. Locally derived from the Wessex  Downs, this incredibly hard form of sandstone was worked by flaking and pecking to form the carefully shaped uprights and lintels of the five trilithons and the sarsen circle, and was used in its natural state for the Heel Stone and at least two of the four station stones.

Stukeley also recognised that what he referred to as the ‘Altar Stone’ at the focus of the monument was a different kind of sandstone ‘still harder, as design’d to resist fire’ as he says in his quaint 18th century style. And what he called the ‘pyramidals’, which we now refer to as the pillars of the Bluestone Circle and the Bluestone Horseshoe, were likewise ‘of a different sort, and much harder than the rest’.

The ‘Stonehenge Layer’

Our excavations within Stonehenge in 2008 (see CA 219) confirmed what earlier excavations had hinted at: namely that the Bluestones started to be broken up and chipped away more or less from the time they were set up in each successive arrangement. The great spread of flakes and debris usually referred to in the archaeological literature as the ‘Stonehenge Layer’ is not, as once thought, the debris from a one-off act of dressing the stones prior to their erection. Instead, these flakes have accumulated over millennia and include evidence for the use of Bluestone to fashion axes. Furthermore, detailed analysis of the finds from our excavations, now well under way, has highlighted two other important points. First, that some kinds of stone that we found as flakes and blocks in the excavated sample are not represented amongst the existing range of pillars standing at the site. Detailed petrological work by Rob Ixer and Richard Bevins has racked the source of one such rock type — a kind of rhyolite — to probable source outcrops near Pont Saeson, on the north side of the Preseli Hills (despite a speculative note in British Archaeology Nov/Dec 2009, page 7, suggesting a source elsewhere in Wales). Second, that interest in the Stonehenge Bluestones did not cease in prehistoric times. In the 4th century AD a shaft was dug adjacent to Bluestone Stone 35a that was refilled with rich dark soil. It was then ritually sealed by the placeme up, would have marked the position of the shaft. Coins, pottery, brooches, surgical instruments, and possibly also a curse-tablet from earlier excavations show that Stonehenge was just as much a sacred spot in Roman times as it had been earlier.

Back to Preseli

Seen this way the Bluestones are an important component of whatever made Stonehenge special. Their meaning, purpose, and role were central to the activities at Stonehenge and gave the site a power of place quite unlike anywhere else in northwest Europe. Decoding their significance means looking not only at Stonehenge, but also at the landscapes around their sources in the Preseli Hills of north Pembrokeshire. The surveys and sample excavations we have carried out there since 2001 as part of the SPACES project (the Strumble-Preseli Ancient Communities and Environment Study) have emphasised connections between source outcrops and water in a way that mirrors the link between Stonehenge and the Avon, formalised by the route of the Stonehenge Avenue. In Preseli, elaborated springheads, some associated with rock art, lie around the outcrops on Carn Menyn. Most significantly, the arrangement of Bluestones at Stonehenge in the early 2nd millennium BC broadly matches the arrangement of stone outcrops in the Preseli landscape.

Detailed characterisation of the Stonehenge

Bluestones and comparison with samples from outcrops in Preseli by a team based in the Open University, backed up by work undertaken by Rob Ixer, shows that the kinds of spotted dolerite exclusively forming the central Bluestone oval/ Bluestone Horseshoe at Stonehenge occur at just a few outcrops along the central spine of the Preseli ridge. Our detailed archaeological surveys show that, of the handful of possible sources, only one, that at Carn Menyn on the highest point of the ridge, displays substantial traces of prehistoric stone extraction and it is here that broken pillarstones, standing stones, and enclosures were also found (CA 212).

The full article can be found in Issue 252 of Current Archaeology


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