Interpretation of Edge Angles to Determine Use of Stone Tools
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meat, plants, woody plants, bark, fresh soft wood, fresh hide |
other wood, fish, dry hide, soft stone, horn |
bone, shell, stone |
Axehead #1 has a edge angle of 38 degrees and Axehead #2 has an edge angle of 38.5 degrees.
The angle is close enough to the 26-35 degree range to say that this stone tool was used for cutting.
When we look at the hardness of the stone (thermally metamorphosed quartzite) which is quite hard; these tools were probably used to cut open soft wood (for native honey, grubs... according to elder Nungbana)
Axehead #3 has an edge angle of 44 degrees which is close enough to the 46-55 degree range to say that this axehead was used for heavy cutting. This makes sense as it is composed of the hardest and strongest rock very fined grained rhyolite lava. One would expect deep scratches on both sides of the edge due to the massive forces involved in heavy cutting; however the axehead has no large scratches. The information is contradictory. One solution lies in the fact that the axehead is very highly polished and unmarked - perhaps it servers a ceremonial or status role. It's source area is some 1100km away - certainly is is an attractive specimen.
Axehead #4 has an edge angle of 49 degrees, the largest of all. This specimen is composed of greywacke , the softest of the metamorphic rocks being derived from "dirty mudstone". As it falls within the 46-55 degree range and is soft; its use was probable as a hide scraper.
Axehead #5 is different to all the others, in that it has no valid edge angle. It was probably used to grind malachite into a green powder for body ornamentation (it could not be used for food as malachite is toxic to humans). We thought that it would be used with one hand at each of the apexes of the rock. This complies with further observations of the stone , in which we found that if the stone was held this way, that there were two working faces, one of which was more polished than the other. We thought that the scratched side would be used in a forward downward method to squash and push the material , then the user would bring back the squashed material with the other side in a sliding motion to grind it finer. It is also possible that the object is not a tool; naturally occurring and just a convenient shape - there is no conclusive evidence of human alteration to this basic shape.