Anth 140
Summer 2007
Raw materials:
Lithic, or chipped stone tools can be made only from a few specific types of rock, all
of which are composed largely of silica (SiO2). These rocks are either amorphous,
meaning that the minerals that compose the rocks have not formed crystals, or
cryptocrystalline, meaning that the minerals have formed patterns of microscopic
crystals. Because these rocks are not composed of large crystalline minerals, they
break much like common glass, yielding conchoidal fractures.
A conchoidal fracture is one in which the fracture surfaces are curved. When the rock
is struck the energy of the blow is distributed evenly, in a radial fashion, away from
the point of contact. This property of fracturing conchoidally is what makes the
production of lithic tools possible.
Definitions:
The practice of producing lithic tools is generally termed flintknapping. Initially, a
stone, called the core, is struck, to break off smaller pieces, the flakes. Depending on
the technology of the flintknapper, either the core or a flake may then be worked into
a finished tool. The flat surface at the top of the flake where it was struck is called the
platform. The platform end is the proximal end of the flake; the end where the flake
terminates is the distal end. The interior surface of a flake, i.e. the surface that was
next to the core, is called the ventral surface; the exterior surface is called the dorsal
surface. Concave surfaces on any stone where flakes have been removed are called
flake scars. Any of the original weathered surface of the stone remaining on the
flakes or core is called cortex. The waste products of flintknapping, including
unwanted flakes, are called debitage.
Courtesy of: http://www.utexas.edu/courses/denbow/labs/lithic2.htm
Anth 140
Summer 2006
Techniques:
Due to conchoidal fracture properties, flakes and cores tend to have distinctive
characteristics that vary with the flintknapping techniques used to produce them. The
three most common techniques are (1) hard hammer percussion, (2) soft hammer
percussion, and (3) pressure flaking.
Hard hammer percussion is the earliest and most basic flintknapping technique,
producing flakes by striking another stone, the hammerstone, against a core. It can
be used to produce finished, but simple, lithic tools from cores, such as the early
handaxes used by Homo erectus, or as a starting point for more elaborate tools
formed either from cores or flakes. A flake struck using hard hammer percussion
frequently has a crushed area on the platform called a point of percussion. Beneath
this on the interior surface of the flake, there will be a swelling, called the bulb of
percussion, caused by the force of the striking blow. Beneath the bulb of percussion,
the force of the blow may have created ripples in the fracture which center around
the bulb of percussion.
Courtesy of: http://www.utexas.edu/courses/denbow/labs/lithic2.htm
Anth 140
Summer 2006
Soft hammer percussion produces flakes by striking the unfinished tool with a soft
hammer, usually a piece of antler, bone, or wood. A soft hammer flake differs from a
hard hammer flake in that it tends to be thin and flat with a small platform, a lip on the
interior of the platform, and a low diffuse bulb of percussion. Because soft hammer
percussion is the easiest way to remove large, thin flakes, is particularly useful in
producing thin bifaces, or lithic tools that have been flaked on both sides.
Pressure flaking produces flakes by using a flaker made of a soft material, such as
antler, bone, wood, or copper to apply force by pressing rather than striking. Pressure
flakes are small and fragile, and are used to thin and shape lithic tools. Many lithic
tools are produced by a combination of all three techniques, with hard hammer
percussion followed by soft hammer percussion and then finished by pressure flaking.
Courtesy of: http://www.utexas.edu/courses/denbow/labs/lithic2.htm