Thursday 19 December 2013

Bluestone Chips, Paper by Ixer and Bevins And A New Discovery

A very interesting paper about the Bluestone chips or debitage at Stonehenge has just been released:



Rob Ixer and Richard Bevins

Within this century there has been a renewed interest in
the lithology of the Stonehenge bluestones, both for the
standing orthostats and also for the vast numbers of broken
bluestone material, now referred to as debitage.
Increasingly it has been recognised that there are a number
of interesting problems associated with this debitage found
within the ‘Stonehenge Landscape’, most notably their
original geographical provenance, their internal Stonehenge
provenance (matching debitage to parent orthostat), the
reason for their presence and finally explanations for the
apparent mismatch between the lithologies of the (aboveground)
bluestone orthostats and the debitage both in terms
of type and numbers....

Full paper and download at

This coincides with Rob Ixer kindly confirming that the bluestones chips pictured below (click to enlarge)look like Preseli Spotted Dolerite - a chemically altered igneous rock containing spots or clusters of plagioclase feldspar.

I discovered this surface scatter in the spoil from animal burrows, the black round object is from a rabbit, last summer.

Over two hundred chips have been seen so far on the surface. It is close to Stonehenge, in the landscape but not within the Stonehenge Triangle. I have of course informed the archaeologists at Stonehenge, and can't tell anyone else the location. Sorry.

UPDATE - They aren't "bluestones", Rob Ixer has done further analysis and provides this Press Release.

Lithics from within the Stonehenge landscape collected by Mr T. Daw.

A selection of small lithics were collected by Mr T. Daw from within the Stonehenge landscape, they were macroscopically identified using x20 magnification. Their uniform but very restricted size range is of note as this would be unusual for Stonehenge debitage.
They comprise a mixture of modern roadstones, mainly fine-grained basalt , altered basalt and felsite, plus a single Stonehenge saccharoidal sarsen. The majority of the lithics are fine-grained igneous and similar in appearance to the spotted dolerites comprising most of the bluestones. Although the lithics are too small to determine macroscopically they appear to include two different types. No non-dolerite bluestone (rhyolite, tuff/ashes, sandstone) was recognised.
Two representative samples were sectioned to determine if either main group of lithics was a Stonehenge bluestone but neither was.  A sample of the abundant white feldspar and one of the rare, white feldspar classes of possible preselite were sectioned and petrographically described in transmitted and reflected light.  Neither thin section showed Preseli Dolerite.
The abundant white feldspar is an altered feldspathic rock possibly a basalt and the rare white feldspar rock is an altered felsite and more acidic carrying primary quartz.
The two sections add to the large number of adventitious lithics-mainly 19th and 20th century roadstones found in the Stonehenge Landscape.
Saccharoidal sarsen                                                                                     1.3g
Purple fine-grained lava same as from Fargo Wood Test Pits             1.9; 0.4g
Black, non-epidote bearing fine-grained dolerite with ?bornite         1.4g
Basalt/micrite                                                                                                0.4g
Abundant white feldspar     basalt                                                             1.1; 0.9g
Few white feldspar                                                                                        1.6; 1.5; 1.0; 0.6g

Rare, white feldspar, some pale green colouration   felsite                  1.6; 1.4; 1.3; 1.2; 3x0.8; 2x0.7;       0.6; 0.4

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