Defining an algorithm to classify Stone artefacts. I Preview
Measuring stone artefacts has been an important task since the beginning of lithic studies in nineteenth century. Since then researchers have spent most of their time measuring stones and looking for new things (I mean variables) to measure.
In the following posts I will show you some interesting variables and results I found during my researches. At the end of this series I will try to summarize most of them in a new algorithm that I hope will help you to classify stone artefacts. Let’s start. Remember, if you want to be updated subscribe to Wikilithics.
Getting ready
First of all, how did I measure the stone artefacts I studied?
For this research I have measured 150 flint and quartzite artefacts (yeah, not so many but enough for a sample). They are all complete flakes. By the way, at the end of the series you’ll be able to download the database I used for your personal use.
Each flake has been scanned and digitally measured. There are a lot of software apps in the web you can use to measure digital images as ImageJ or Digimizer. I used instead a CAD plugin for Adobe Illustrator. A cool thing you can do with this kind of software, is to measure areas and perimeters with high accuracy.
Artefact orientation is a key point in all lithic studies and probably one of the main sources of error, so I will show you how I’ve orientated each artefact.
Well I know, we need a reference axis to start. I have used the intersection between the striking platform and the ventral surface as the main axis. The Length is measured perpendicular to this axis, and the width is parallel to it. Thickness is orthogonally measured to length and width.
I have measured the following variables:
-Maximum length (ML): From the reference axis to the most distal end.
-Maximum width (MW): From the outer left margin to the outer right margin.
-Maximum thickness (MT): From the outer ventral surface to the outer dorsal surface.
-Length from the striking point (Lsp): From the striking point to the distal end.
-Width (Wm) and Thickness (Tm) at the midpoint of the ventral surface area.
-Ventral surface Perimeter (VP) and ventral surface Area (VA).
-Estimated cutting edge (ECE): calculated as the difference between the VP and the length of the blunt margins (for instance, the backed edges or the striking platform).
As you can see all these variables are measuring the ventral surface of the flake. What I'm really measuring in this way are the dimensions of the fracture plane, I mean the surface generated by the hammer impact. Keep in mind for future posts. Let's continue.
-Maximum Platform Depth (MPD): From the intersection of the striking platform and the ventral surface to the intersection of the striking platform and the dorsal surface. Measured perpendicular to the reference axis.
-Maximum Platform Width (MPW): From the outer left margin of the striking platform to the outer right margin of this surface. Parallel to reference axis.
-Platform depth from the striking point (PDsp).
-Platform width at the midpoint of the Depth axis (PWm).
-Platform Perimeter (PP) and platform Area (PA).
-Exterior platform angle (EPA): the angle formed by the intersection of the striking platform and the dorsal surface of the flake.
-and finally we register the Weight (W) of the flake.
In addition to these measures I have calculated some interesting ratios that I will show you throughout the next posts.
See you soon.
