But I was wrong.
I have done some more detective work. In 1989 the OU team (which included Rob Ixer) examined as many bluestone fragments as they could find, including one that they referred to as RSN18 - ENQ2305. They admitted that they did not know where it had come from, and there was no mention in their text of Newall’s boulder. They renamed it OU2 and the analysis showed it to be a typical blue-grey rhyolite from the north slopes of Mynydd Preseli. However, they listed the sampled rock fragment as having dimensions 10 cm x 7 cm x 3.4 cm and a weight of 244 gm. The Newall boulder with which we are concerned does not have those dimensions and it is certainly not a blue-grey rhyolite. It is, according to Harrison, a dark blue / blackish flinty welded tuff. The boulder dimensions are c 22 cm x 15 cm x 10m cm, and I guess its weight as being around 10 kg. The OU team did not examine the smaller cut IGS boulder sample either, since that has dimensions c 8 cm x 4 cm x 6 cm — ie considerably smaller than OU2. We know that the IGS staff examined at least five samples / thin sections from the Newall collection, since there is a reference in correspondence to a sample numbered ENQ2301. We also know that the record keeping was somewhat chaotic, and in one letter to Kellaway, Newall referred to his notes and labels being eaten by mice while the samples were stored in his attic……..
I think that the sample examined by the OU team came from one of the other smaller samples (of a quite different rock type) that has now found its way into the Salisbury Museum collection.
So we can reject that 1991 reference as unreliable, and concentrate on the examinations of the boulder by RK Harrison, Geoffrey Kellaway, R Sanderson and BR Young. They all handled the boulder, took samples from it, knew its provenance in the Hawley Stonehenge dig, and discussed among themselves and with Newall where it might have come from. I have on the file some very interesting correspondence. So the Stonehenge provenance is, as they say, rock solid…….. and far more reliable than the provenances of many of the other fragments collected from Stonehenge digs. That is all that matters.
PS. I have noticed that the text painted onto the rock says RSN18. But the bit that says ENQ2301 is on a sticky label. Shall we guess that when Newall handed over his samples to Salisbury Museum in 1976, with many of the labels missing because the mouse in the attic had eaten them, new labels had to be written out and appended to assorted lumps of rock? And shall we guess that somebody inadvertently put the wrong label onto the Newall Boulder?