by Brittany Blanchard – CART Archaeological Technician
Creating stone tools is a reductive process called “chaîne opératoire” where a knapper, an individual skilled in lithic reduction, forms a rock into smaller, sharp tools by chipping away until the desired shape is achieved. In the field and lab, archaeologists encounter both the stone tools and the fragments of stone that have been knocked off during manufacture. Click here to learn more about lithic production. Archaeologists can interpret broken stone as either the result of cultural or natural forces. Natural fracturing of lithic materials from forces such as freezing and thawing (cryoturbation) can be separated from purposefully fractured stone on the basis of morphological attributes associated with flint knapping. High quality materials such as chert, jasper, and chalcedony retain these attributes in the lithic debitage, the rock debris from the manufacture of stone tools. A type of debitage is called a lithic flake and takes a trained eye to distinguish from other stone fragments.
A lithic flake is “a thin flat asymmetrical piece of flint or other stone which was intentionally removed from a tool or projectile core during the process of manufacture or sharpening/resharpening” (Gumbus 2019). Flakes exhibit unique characteristics that are the direct result of the processes used when making a stone tool. Archaeologists use three main attributes to classify flakes from naturally fractured stone: the striking platform, the bulb of percussion, and what is sometimes referred to as ripples or waves.
Typically flakes are relatively thin with a slight curvature and three sharp edges that feather out. The fourth edge is the striking platform. This is where blunt force was used to hit the rock and separate the flake from it. A harder rock or sturdy piece of antler could be used to achieve this.
The pressure during impact produces a Hertzian cone that forms the bulb of percussion, a swelling or “bulb” along the inner or ventral side below the striking platform. This force also produces a negative scar on the surface of the rock where the flake was removed. The last attribute, is the ripples or waves that radiate away from the point of impact on the ventral surface. The ripples are a result of the shock wave that runs through the stone when it is struck.
Studying the amount of cortex and number of negative flake scars on the outer surface of a flake can help determine how far along the knapper would have been in shaping a tool. When a rock is selected to be shaped into a tool, it can show weathering from exposure to the elements in its natural setting. The outer portion, called the cortex, can be visible on flakes removed from rocks subjected to weathering.
“The first flake removed from a piece of raw material, which will preserve cortex on its entire exterior surface, is called a cortical or primary flake . . . As further flakes are removed from the core they will show diminishing, though variable, amounts of cortex on their exterior surfaces because their exterior surfaces will be partially or completely composed of previous flake scares. These are often called secondary flakes” (Debénath and Dibble 1994).
Some rocks are retrieved from quarries or outcrops and will not have evidence of weathering on its exterior so negative flake scars can help determine at which stage of reduction the knapper removed the flake. Fewer flake scars on the external surface would indicate that the flake was removed earlier in the process while many flake scars occur as the knapper further shapes the tool.
Flakes can appear in various sizes depending on what stone resources are available and the knapper’s intentions for the tool. Partly, this occurs because different rocks fracture in different ways. Additionally, the intended size of the finished tool will result in larger or smaller flakes. If the knapper is making a large hand axe or cutting tool, then they may choose a large piece of raw material to begin with and large flakes would be removed during the process of making the tool. Alternatively, smaller tools will begin with a smaller rock that results in smaller flakes chipped away during manufacture.
Debénath, A. and Dibble, H. L. 1994 Handbook of Paleolithic Typology. Vol. I. University Museum, University of Pennsylvania, Philadelphia.
Gumbus, A. 2009 Lithics-Net’s Glossary of Lithics Terminology. Web Page, http://www.lithicsnet.com/glossary.html, accessed January 16, 2019.
Koons, S. 2015 CART Lithic Analysis 101: An Introduction to Cataloging Lithic Artifacts. Video, Archaeology and Collections Branch Fairfax County Park Authority files, accessed January 16, 2019.