Over and again on this blog, I have examined the published "evidence" for Neolithic bluestone monolith quarrying in Pembrokeshire, and have found it wanting. With the extraordinary (in the sense that it is difficult to comprehend) backing of geologists Robert Ixer and Richard Bevins (and a few other geologists brought in as specialists in assorted techniques) Mike Parker Pearson and his fellow archaeologists have flogged to death the idea of Neolithic quarrying at Rhosyfelin and Carn Goedog. They are now apparently about to look for more "quarries". They have refused to acknowledge that there is any dissent from their quarrying hypothesis either inside or outside of the specialist peer-reviewed literature, and their "bluestone myth" has been developed and enlarged year on year so that it now incorporates a lost "giant stone circle" at Waun Mawn and a wildly convoluted narrative. I think it is true to say that many independent observers have finally decided that enough is enough, and have come to the same conclusion as me -- that the evidence presented by MPP in that appalling TV programme fronted by Alice Roberts, and in the literature, is so ludicrous as to be embarrassing.
** There are 31 dolerite orthostats, of which 14 were sampled in 1991 and 2008. Some are standing stones and some are stumps. Some are spotted and some are unspotted. The spots are now thought to be not felspars but aggregations or clusters of low grade, secondary metamorphic minerals. Bevins, Ixer and Pearce (2014) analysed 22 Stonehenge dolerite samples, and suggested that they were clustered into three groups, with one sample petrologically distinct from all three. So there are three groups and one outlier -- four types. Every one of the 22 samples is unique, and the possibility must be entertained that every one has come from a different geographical location in eastern Preseli.
** There are four above-ground volcanic rocks in the orthostat collection (stones 38, 40, 46 and 48). There seem to be four distinct types - two dacites and two rhyolites. They are referred to by the geologists as rhyolitic tuffs, foliated rhyolitic tuffs, crystal-lithic-vitric tuffs, and argillaceous tuffs. They have come from four different north Pembrokeshire locations. Stone 38 has an unusual mineralogy including graphitising carbon.
** There is not much debris to match the 4 volcanic rock orthostats in the Stonehenge debitage, but similar fragments are found in the great cursus field. In the debitage, unique volcanic material has been classified as belonging to two types -- Volcanic Group A and Volcanic group B. None of the potential parent orthostats for Volcanic Group A (32c, 33e, 33f, 40c and 41d) have been petrographically examined, making it impossible to relate this debitage to any (or all) of the buried stones. Ixer and Bevins (2016) say: ".........on present knowledge the origin(s) of the Volcanic Group A lithics is still expected to be found within the Ordovician volcanic sequences in the north Pembrokeshire area on the northern side of the Mynydd Preseli range probably amongst those outcrops examined by Evans (1945)."
** There are two micaceous sandstone stumps -- numbered 40g and 42c. There are also lumps of Lower Palaeozoic sandstone scattered about in the debitage -- the largest lump weighs c 8.5 kg. There appear to be two types, with possible sources in the Lower Palaeozoic rocks of north-west Pembrokeshire.
** The Altar Stone (stone 80) is a greenish calcareous sandstone, probably from the Senni Beds of Carmarthenshire or Powys. (It is not from Milford Haven.) So just one rock type here. There is some debitage related to this stone, but it cannot be established that the fragments came from the Altar Stone itself (Ixer and Bevins, 2013). The most feasible provenance for the stone is the Laugharne - Craig Ddu -- Llansteffan area of Carmerthenshire.
** In the debitage there are many fragments of rhyolites, some with planar fabrics -- and most matching closely (but not perfectly) the rock outcrops of the Craig Rhosyfelin district. There appear to be three distinct groups of "rhyolites with fabric", all assumed to have come from the Pont Saeson area. There may be a match with orthostat 32e or 32d (Ixer and Bevins, 2011), but the debris analyses does not match any of the known volcanic orthostats.
** There are also some basic tuffs in the collection of fragments from the debitage -- two lithologically different types (Ixer and Bevins, 2013). These are probably also from the Fishguard Volcanic Series.
** Other lithics in the stone collections from the debitage (eg. haematite (from the Reading Beds?), greensand, slate, limestones, Mesozoic sandstones and gabbros) appear genuine, and need further research.
To sum up:
Ixer and Bevins (2014) claim that there are “about ten types of bluestone” represented in the orthostat / debitage samples, but they also show in assorted articles that these have nonetheless come from at least 20 different locations. It is estimated on the basis of the above points that there are at least 30 different rock types represented in the full "bluestone assemblage" -- especially when due respect is given in this count to cobbles as well as orthostats and flakes, for reasons frequently recited on this blog.
It should also be noted that the majority of the 43 bluestone monoliths/stumps at Stonehenge have still not been sampled and analysed. The new work reinforces the idea that the Stonehenge bluestone assemblage is made up entirely of rock types from the west, and that they have come mostly from north Pembrokeshire.