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Tuesday, 7 September 2010

What is Preselite?




I have banged on for years about the continued use of the term "Bluestone". OK -- I suppose I use the term as much as anybody else, but this is my definition: "Any stone on Salisbury Plain that is demonstrably not from the immediate neighbourhood." So I am talking about FOREIGN stones or erratics, sticking close to the dictionary definition of the word "erratic" -- but others use the word "bluestone" as if it is a learned geological term, which it most emphatically is not........ The word "bluestone" tells us nothing about petrography or lithology, colour or origin.

Now I'm getting equally confused about the use of the term "Preselite" -- it also tends to be used as if it is a geological term, which it is not. I would classify it as another pseudo-scientific term......

The term is used particularly with respect to polished axe-heads purportedly from the Preseli Hills area, but geologists also use the term. These are the axe lithologies / types normally referred to in the literature:

Group XIII Spotted dolerite or preselite. Source in the
Preselau Hills, Pembrokeshire (Dyfed). Rare, but
important as ‘Blue Stones’ of Stonehenge. Stone
and Wallis, PPS, 17 (1951), 128. See also Group
XXIII.

Group XXIII Ranges from graphic pyroxene granodiorite
(Group XXIIIa) to quartz dolerite (Group XXIIIb).
Source area between Preselau Hills and St David’s
Head, Pembrokeshire (Dyfed). Group XIII is an
individual rock type which falls within the petrological
and geographical range of Group XXIII. It
might have been classed as a subgroup of XXIII
but for its prior publication as a group in its own
right. Rare. Shotton in Prehistoric Man in Wales
and the West (eds Lynch & Burgess), (1972), 89.

Can anybody give me a precise definition of the word "Preselite", which will help us all to use it accurately?

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