New paper on Bluestone 38

 

 

Altar Stone (top), Stone 38 (middle) and Stone 48 (bottom) -  thanks to the Stones of Stonehenge site for the photos.  These stones are neither rhyolitic tuffs nor dolerites, spotted or otherwise.  Look at the extraordinary markings on the surface of the Altar Stone -- more on this later.....

The new paper refers to Stone 38 and related debitage.

More images:

Stone 80 (Altar Stone)
http://www.stonesofstonehenge.org.uk/search/label/Altar%20Stone

Stone 38
http://www.stonesofstonehenge.org.uk/search/label/Stone%20038

Stone 48
http://www.stonesofstonehenge.org.uk/search/label/Stone%20048

There's a new paper from Ixer, Bevins and Gize on the subject of Bluestone 38 and the related debitage at Stonehenge -- which might, or might not, have come from the stone itself. Once again, an interesting piece of work which increases our understanding of the widsespread provenances of the weird bluestone assemblage.

Hard ‘Volcanics with sub-planar texture’ in the Stonehenge Landscape by Rob A. Ixer, Richard E. Bevins and Andy P. Giże
Wilts Arch & Nat Hist Mag 108 (2015), pp 1-14

Volcanics with sub-planar texture -- twelve fragments have been examined. They are "small, often sub-rounded, rather than angular flaked, fragments throughout Stonehenge and its environs ....."  And there is quite a wide distribution of fragments across the landscape.  Stone 38 itself is a strange little one, quite unsuitable to be counted as a fallen orthostat -- it's more like a mis-shapen boulder, and like  Stone 48 it's best described as a glacial erratic, pretty worthless for incorporation into a megalithic monument, but simply used because it was there........

Quote: These volcanics comprise two groups namely Volcanic Group A, friable rocks with abundant white mica and a strong metamorphic fabric and Volcanic Group B, hard rocks that are partially characterised by an unusual mineralogy including two forms of graphitising carbon. Only twelve Volcanic Group B samples have been recognised from the Stonehenge debitage but they share the same petrography as Orthostat SH38. Spatially, as with the debitage from the Altar Stone and Orthostat SH48, they are widely, if thinly and randomly, distributed throughout the Stonehenge Landscape. Temporally, almost none of the debitage, from all three bluestone orthostats, has a secure Neolithic context. 

Quote:
 
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Conclusions 

Orthostat SH38 and twelve pieces of debitage that constitute the new Volcanic Group B class of debitage are sufficiently uniform in terms of their mineralogy, grain size and textures that it seems probable that they are all from the same rock rather than just from the same outcrop.

Although this debitage is numerically rare it has a wide spatial distribution in the Stonehenge Landscape notably within the Darvill and Wainwright April 2008 excavation and Heelstone Ditch but also including within Trench 45 in The Avenue and Aubrey Hole 7 in Stonehenge. Although a lithic with graphitising carbon was found from close to the Stonehenge Greater Cursus no SH38 debitage has been recognised from there with any certainty. The SH38 debitage distribution is similar to that found for orthostat SH48 but is more extensive than that for the Altar Stone.

The temporal distribution of the SH38 debitage is very similar to that for SH48 in that most pieces are found from post Neolithic contexts but are less ‘bunched’ than that from the Altar Stone.

The newly reported SH38 debitage has extended the range of petrographical features beyond those seen in orthostat SH38, notably to include the presence of large zircons, rare earth-bearing minerals, tube pumice and a significant fine-grained siliceous component. This in turn suggests that were the single geochemical analysis for SH38 (Thorpe et al. 1991) and taken from a very small sample , to be augmented by new analyses from the present samples, a geochemistry that was closer to the bulk geochemistry for SH38 could be achieved. An enhanced petrography plus a more representative geochemistry would help to narrow the possible geographical sources for the orthostat. On present knowledge this is still expected to be found within the Ordovician Volcanic sequences, in the north Pembrokeshire area but the net is tightening.