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Stone Tools in the Lab

Methods applied to stone tools in a lab environment with the intention of extracting evidence
So after we get back from Liang Bua, the artefacts are eventually delivered to the laboratory here. When they get here, they haven’t been touched. They’ve been air dried, and they’ve been wrapped up. And as we unwrap them, we’re careful not to touch them at all. We have gloves on, and so they’re un-contaminated. The next step is to take photographs and record what we’ve got before we even touch the dirt or the artefacts. And we document carefully which side of the artefact is up and which is down. And then we remove that artefact and take an image of the sediment because what’s important here is what the artefacts are actually touching. So sometimes they’re leaning against bits of bone.
It might be a stegadon bone, or it might be a bird bone, or it might be just little bits of rat or bat bone that are in the cave there. Some of them might have to do with what the artefact was used for, or it might not. So it’s very important to document that detail. And we can say that when we lift up the artefact, we can see exactly what’s underneath it. So the next step is to photograph the artefact, photograph what it looks like underneath, then turn the artefact over to the underside, that side that was actually touching the bottom bit that we just photographed on the sediment pedestal.
So we photograph that as well, and then we’ve got a really good documentation of exactly what’s there. So the next step after we’ve done the photography is actually take some samples. Now, these can then be analysed because at different stages of the analysis, we can document what are the lipids or the chemical composition of the soil and see if that’s the same as what we’re actually finding on the artefact. Then we can take an initial look at the artefact itself, and that’s done under, initially, low-powered microscopy. And with that, we can see obvious things like roots, or we can see any damage on the edge of the artifact, scarring.
Or sometimes we can see alignments, and we can see different aspects that might be useful in interpreting what the tool was used for, but also the kinds of things that it might have come into contact with. And once we’ve actually noticed some very specific things at the relatively low magnification, we can move to higher magnification. So on the surface, we can see things like scratch marks, which show us the directionality and how something’s been used, whether it’s been used parallel to the edge of the artefact or it might be used for scraping, using it perpendicular to the edge, or it might be used for chopping or drilling.
All these different activities can be determined by orientation of these scratch marks or striations, and the angles of the actual scars, the scars and flake scars on the edges, and the amount of rounding. And we can also look at the polish. So what would happen after we’ve done this preliminary look, before it’s been washed at low power and at high power magnification, we then pass it on to Luke, who’s going to be looking at vibrational spectroscopy on this place. And that includes Raman and FTIR. So these vibrational spectroscopy techniques that can identify with a laser very, very small particles and potentially identify their origin, whether they’re plants or animal proteins or lipids.
Now, once he’s done that, the artefact comes back to us again, and then we can look at it on a clean surface after it’s actually been washed. Now, that then allows us to look at polished surfaces in a lot more detail. And the polishes on the edge can be sometimes diagnostic of whether it’s been used on certain classes of material– so a siliceous plant material, or wood, or bone, or shell, or other sorts of broad classes of material. We can start looking at those things in a lot more detail, document them, and make pretty accurate predictions about the tasks that were performed with that particular piece.

Once excavated, artefacts are carefully air-dried and wrapped to avoid being touched. Similarly, when they are delivered to the lab, gloves are worn, so that the artefacts remain untouched and uncontaminated. A series of procedures are then followed…

The following methods are applied to stone tools in a lab environment to extract evidence that addresses the following questions about the artefacts:

  • What were they used for?
  • What did they come into contact with?

1. Photography

Photographs and careful documentation of observations of the artefact in its raw form are captured. The artefact is removed, the surrounding sediments are photographed, and the artefact is photographed from every angle.

2. Taking samples

Samples are extracted from the surface of the artefact and the surrounding sediments for analysis of organic molecules (e.g. lipids) and the chemical composition of the sediments.

3. Microscopy and washing of artefact

The artefact is viewed (before and after washing) under low-powered magnification to identify obvious roots, damage, scarring features etc. It is then viewed under higher magnification to identify the orientation of scratch marks or striations, the nature and angle of scars, polish from use, and the amount of rounding of the use-wear traces.

4. Spectroscopy

An artefact may then be passed on for further analysis using ‘vibrational spectroscopy’ (Raman and FTIR), which is a technique that uses scattered and reflected light to identify the chemical composition of particles (e.g. proteins, lipids, carbohydrates).

5. Analysis of cleaned surfaces of washed artefacts

After microscopy and spectroscopy observations, documentation of the artefact’s polished surfaces takes place to add further insights to the past use of the artefact.

Conversation starter

  • Why is it important that the artefact remains untouched?

  • Why is it important to consider the sediments with which the artefact has come into contact?

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