I drove past Bethel Chapel in Mynachlogddu today, and was forcefully reminded of the way in which spotted dolerites from the nearby outcrops of Carn Meini etc have been used in local architecture. The whole of the chapel facade (finished in 1875) is built of shaped blocks of spotted dolerite -- many different types. Big spots, little spots, scattered spots, dense spots, white ones and cream ones, and so on and so on.
This stone must have been incredibly difficult to work, but somehow or other the faithful builders of the chapel have managed to make most of the blocks rectangular. The only stones that are NOT spotted dolerite are the window cills and lintels, and those curved window surrounds -- those are all, I think, made from soft grey local slate which is very easy to work and shape.
I dare say that Rob or Richard could give a comprehensive geology lesson on spotted dolerites without having to move away from the churchyard. I don't know enough about these different types to know which outcrops they were taken from -- but there are historical records of decisions being made by the chapel deacons to go up onto Preseli to collect stone, and of horses and carts coming down with loads specifically for the chapel restoration.
Here are some close-ups. In some cases the weathered surface has been left, giving a nice rusty or buff colouring, and in other cases the blue-grey of the fresh worked surface is quite striking:
You can click to enlarge any of these photos. What interests me here is the question of WHY, in or around 1870 -75, the congregation here chose local spotted dolerite for their chapel facade. Did it have any particular religious or spiritual significance for them? I doubt that very much -- chapels were generally built with stone that was cheap and durable, and attractive -- they obviously wanted their chapel to be striking, as an offering to the glory of God. But if sandstone or limestone had been the local rock, they would have used that instead. And it WAS cheap -- they needed to pay nothing for it, for there it was, within a mile or two, up on the common, ready to be carted away.
Interestingly enough, in the years 1946-48, during the famous local episode called "The Battle of Preseli", local ministers and political leaders created a great campaign to resist the efforts by the MOD to turn the whole of Preseli into a military training range, by building on HH Thomas's thesis of "the sacred stones." It suited their campaign strategy very well to claim that the spotted dolerites were sacred, and always had been, and that it would be an outrage and an insult to the sensitivities of the Welsh if the MOD had gone ahead with its plans. Shock! Horror! Military firing range planned for sacred Welsh mountains......!!
Anyway, it worked. Churchill and the rest of the Government of the day were swayed by this emotional and pseudo-spiritual argument, and chose Castlemartin and the Brecon Beacons instead. That doesn't alter the fact that the campaign to save Preseli was based on spiritual mumbo-jumbo, conjured out of thin air by the bards and religious leaders of the day....... all credit to them, for in reality there never was any great feeling in history that either the spotted dolerite or Preseli had anything sacred about them. They had MYTHOLOGICAL connections, of course, since the uplands figure prominently in the Mabinogion -- but so do many other places in Pembrokeshire, and you could argue that Cwm Cych, Narberth and the Pembrokeshire Islands were much more "special" than Preseli in the minds of the medieval storytellers.