David Field, Hugo Anderson-Whymark, Neil Linford, Martyn Barber, Mark Bowden, Paul Linford, Peter Topping, , Marcus Abbott, Paul Bryan, Deborah Cunliffe, Caroline Hardie, Louise Martin, Andy Payne, Trevor Pearson, Fiona Small, Nicky Smith, Sharon Soutar and Helen Winton (2015). Analytical Surveys of Stonehenge and its Environs, 2009–2013:
Non-invasive survey in the Stonehenge ‘Triangle’, Amesbury, Wiltshire, has highlighted a number of features that have a significant bearing on the interpretation of the site. Geophysical anomalies may signal the position of buried stones adding to the possibility of former stone arrangements, while laser scanning has provided detail on the manner in which the stones have been dressed; some subsequently carved with axe and dagger symbols. The probability that a lintelled bluestone trilithon formed an entrance in the north-east is signposted. This work has added detail that allows discussion on the question of whether the sarsen circle was a completed structure, although it is by no means conclusive in this respect. Instead, it is suggested that it was built as a façade, with other parts of the circuit added and with an entrance in the south.
"Eighty-six stones are visible at Stonehenge, including four stumps (Fig. 2); the 20th century excavations revealed a further ten buried stumps making 96 in all. These stones are coarsely divided between the sarsens, a hard sedimentary silcrete, and the ‘bluestones’, a catch-all term covering a variety of rock types of distant origin including spotted/unspotted dolerite, rhyolites/rhyolitic tuffs (Ixer & Bevins 2011; Bevins et al. 2012), volcanic ashes, a Devonian sandstone (the Altar Stone), and other sandstones (Thorpe et al. 1991)."
Concerning the sarsens and the recent attempts to designate "origins" on the Marlborough Downs and other distant localities: Quote: "Flinders Petrie in particular, who carefully surveyed the stones and whose numbering system is used here, considered that the very position of Stonehenge may have been determined by the presence of a quantity of sarsen (Petrie 1880), while William Gowland (1902, 75, 115), who excavated at Stonehenge at the outset of the 20th century, similarly thought the stones were brought from ‘no great distance from the spot where the structure stands’. The geologist Prof. J. W. Judd (1902, 115–6) considered that they had been moved ‘only a few hundred yards’, while H. H. Thomas (1923, 242) also thought that they may have come from ‘the site of Stonehenge itself’. Johnson (2008, 121) has suggested that the Heelstone is too awkward and bulky a shape to move on rollers and it, at least, is unlikely to have travelled far. Equally the much smaller Station Stones could easily have a local origin: it is, after all, possible to find larger stones on Salisbury Plain without having to travel to the Marlborough Downs for them."
"Assuming that dolerite has a specific gravity of 3, the above-ground weight of the pillars in the Bluestone Horseshoe ranges between 0.96 (Stone 61) and 2.16 tons (Stone 69). As excavation of stones 68, 69 and 70 revealed that between 33% and 40% lay below ground; their estimated weight might be 3.35 tons, 3.24 tons and 2.05 tons, respectively. Stones in the Bluestone Circle are typically not as tall as those in the Bluestone Horseshoe and, due to the numbers that are broken or fallen, it is not possibly to calculate their average weight. In any case they decrease in size towards the north-east. Stone 33, however, has an above-ground weight of 0.51 tons and excavation revealed that c. 1.03 m of it was below ground, allowing its total weight to be estimated at 0.82 tons. In contrast, the above-ground portions of Stones 49 and 31 weigh 1.11 tons and 2.04 tons respectively, and excavated profiles indicate that 39% and 45% of the respective stones was below ground, allowing their total weights to be estimated at 1.82 tons and 3.72 tons."