A core is any piece of material that has had flakes removed from it. Thus,
a core could be used only as a source of sharp flakes, as in this example. At
other times, cores themselves might also be made into tools, in which case the
resulting tool is called a core tool.
A flake is any material removed from a core, whether intentional or not.
In some cases, the flakes themselves were meant to serve as tools. In other
cases, the flake is further modified to make a tool. At other times, the flakes
may just be the waste material from shaping, thinning, or resharpening a stone
tool. This waste material is called debitage, and is one of the most important
collections of lithic material that archaeologists study. By studying the waste
flakes and failures, we can actually reconstruct the prehistoric production
technology and gain valuable insight into an important component of prehistoric
The flake scar is the concave surface left on a core after a flake has been
removed from it. The flake scar will show the reverse image of the bulb of
percussion on the flake, and will also exhibit ripples on occasion. The flake
scar is equivalent to the hole left in the window pane from our last example.
The cortex of a core or flake is the weathered, outer surface of the rock.
Archaeologists often examine flakes to determine the amount of cortex on them in
order to gauge the stage of manufacture and the degree to which cores were being
used to exhaustion.
The striking platform is the prepared surface on both the flake and the
core where the blow that detached the flake was struck. Striking platforms will
have different characteristics depending on the technique that was used to
remove the flake. For example, on this flake and core, the striking platform
has only one surface, and is quite wide, indicating that the flintknapper wanted
to detach a large, thick flake. The platform will often have half of a ring
fracture right at the exact point where the detaching blow was struck.
The errailure is a French term denoting a subsidiary flake scar on the bulb
of percussion of a flake. These scars occur as a result of excessive force
being applied in the removal of the flake. The bulb of percussion is compressed
so much that its elastic response is violent enough to cast secondary flakes off
Bulb of Percussion
The bulb of percussion is the conic section resulting from the fracturing
of the rock. Depending on the amount of force in the detaching blow, the bulb
of percussion can be very pronounced. The bulb is the result of the compression
of the rock due to impact, and it is the elastic rebound from this compression
that actually detaches the flake from the core.
Ripples can often be observed on flakes made of obsidian and other very
fine-grained materials. These radiating waves in the stone are actually
deformations of the rock resulting from the shock wave that accompanied the
detaching blow. They look like frozen ripples on a pond after a pebble has been
tossed into it.
Hatchure lines occur in flakes where extreme force was used in their
removal from the core. The lines are actually hairline cracks resulting from
interference shock waves bouncing around within the rock before the flake
actually detaches itself. In the most extreme cases, these interfering shock
waves can actually cause the flake to shatter as it is being detached.