This is what you write in the final site report when you need to find an archaeologically acceptable way of saying you have thrown something away. As in – ‘A 100% sample of the tile fragments from the 19th century pit deposits was collected and weighed but these were then not retained for further analysis.’ The sub-text being, of course, why did we ever pick them up in the first place?
The worked stone artefacts have been in the firing line for non-retention this week. This is entirely because it is so difficult for a non-specialist (like me) to reliably recognise the difference between very small fragments produced when people make stone tools and the very small fragments produced by a whole range of natural processes. When you are digging you naturally err on the side of caution and pick up everything which looks remotely plausible. This means, once you do get a specialist opinion, you will inevitably finish up throwing some of them away.
Prehistoric stone tools are all basically made in the same way. ‘The secret is to bang the rocks together’ – as it says in The Hitch-hikers Guide to the Galaxy. You need a very fine-grained stone which fractures in a smooth predictable way and something hard to hit it with. This hammer can be another stone or a piece of antler. If you were to hit the centre of your raw material with this hammer the force from the impact would travel smoothly through the stone, spreading out in a conical shape from the point of impact. The trick with flint-knapping is to make glancing blows so that most of this cone is outside the raw material, in the fresh air, and you remove a thin segment from the edge of the stone you are working. These segments are called ‘flakes’ and the process leaves recognisable scars and traces both on the flakes and on the block they were removed from – the ‘core’. By repeating this process over and over again, and through careful choice of the original block of stone being worked, all the vast array of different kinds of prehistoric stone tools were produced.
There are lots of different kinds of stone which can be worked in this way. The finest are the natural volcanic glasses such as obsidian. Incidentally manufactured glass can be worked like this too – I have watch experimental archaeologists make very convincing scrapers from the bases of old beer bottles. Flint is not a volcanic glass, it is a sedimentary rock formed within chalk deposits. However, the peculiar way it forms means that its structure is very fine-grained and even. It is also relatively common and so is the most widely worked rock in prehistory. Of course, there are no deposits of chalk in Lancashire and therefore no flint, except little bits that wash up on the beach. However, cherts form in limestone in a very similar way to flint and the finer ones are good enough to be worked in the same way. As I said a couple of weeks ago about 80% of our worked stone from the New Laund Enclosure is chert and this varies from very fine black stone to extremely granular chunks that you wonder how anyone, however skilled they were, could have worked them at all.
Because of the intractable nature of the raw material the study of stone tool assemblages made of chert is even more specialised than normal. This week we’ve been very lucky to have Alex Whitlock from Pendle Heritage Centre Archaeology Group and Stuart Noon, who is one of the Cumbria and Lancashire Finds Liaison Officers, to go through our worked stone and look at what we’ve got. These are Alex’s photos of a flint flake from trench C and a chert scraper from trench D.
One result of this has been a certain amount of discarding things we collected but which, once they are washed and looked at with the expert eye, can now be seen not to be worked. They have also re-categorised the material into actual tools, flakes and pieces which have had one or more flakes knocked off them. One of the most interesting things to come out of this is that Alex and Stuart have identified Mesolithic (Middle Stone Age – about 9600 – 4000 BC) techniques and tools in the collection as well as a lot of Early Bronze Age material. I think that this is likely to mean that the features in trench D are part of an Early Bronze Age monument but that there was a temporary hunting camp in the area much earlier in Prehistory.
Of course, now that Alex and Stuart have done all this work then the distribution plot of lithics I put up two weeks ago needs revising again. This is the most recent version; blue is chert and brown is flint, diamonds are debitage, squares are tools and the cores/bits with flakes removed are the circles. Some bits have, of course, now disappeared from the plot as we no longer believe in them.