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Wednesday 3 August 2016

The Pensarn mound

Me pointing at the top of the Pensarn mound.  As you can see, it is just a gentle rise in the field, with a summit maybe 1m higher than the surrounding field level.

I went to take a look at it with Chris today, and it's not exactly spectacular.  When we arrived there the field was full of cows with small calves, and so we decided not to go and check out the mound, but to go and have a chat with the local farmer's wife.  But then miraculously all the cows and calves disappeared, and we had the field to ourselves.  Put it down to the fairies........

The mound is approx 25m across, and appears roughly circular, and it's in the field which sits on the highest part of a little plateau, with glorious views in all directions.  Grid ref SN 124358.  The field is well drained, and here and there one finds fragments of foliated rhyolite on the surface.  If the field was to be freshly ploughed, broken fragments of this rock would predominate, together with bits of dolerite.  Both rock types are seen in the hedgerows round about.  My guess is that rhyolite is the bedrock type here.

The best guess is that this is a heavily aggraded Bronze Age burial mound like many others in the area, especially on the summit ridge of Preseli.  It might well have been much more prominent originally, but after many  centuries of erosion and maybe deliberate and accidental destruction by animals, ploughing etc, there is nothing much left.  A guess is that it was maybe 10m in diameter and maybe 3m high originally, and that it has now degraded down to this very low feature with stones and soil spread out to a diameter of c 25m.  Another guess is that it is made of smallish rhyolite and dolerite stones collected locally -- although there may be larger slabs in the core.

Chris also drew my attention to a very fine standing stone in the field adjacent to the main road, about 300m to the north.  It's made of foliated rhyolite very similar to that of Rhosyfelin.  Could it have come from Rhosyfelin?  It's possible, but there are many other outcrops of this rock within and around the valley of the Brynberian river in this district, and it could well have been simply picked up from the ground surface more or less where it was erected. A thin sectioned sample from this standing stone could well be of interest, if Richard and Rob have not examined one already........

Three photos of the Crosswell standing stone at SN122363.  It is quite a slim pillar, tapering slightly, with sharp edges in spite of constant use and polishing by farm animals.  On one of the faces, coinciding with a fracture plane, there are traces of a quartz vein which has mostly flaked away.  Some good fracture scars are visible, some of them slightly conchoidal.  The top of the stone is broken by fractures but the foliations in the rhyolite are clearly visible.

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